Results of College Supplementary Exam 2017 (Council Meeting 25 January 2018)

 

Exam No.	Result
E17109	PASS

 

An overview of NMO Spectrum Disorder and the diagnostic utility of anti-NMO antibodies

 

Volume 13, Issue 1 December 2017  (download full article in pdf)

 

Editorial note

NMOSD is an immune mediated demyelinating disease. Though its clinical presentation may overlap with multiple sclerosis, distinguishing these two entities is important in view of differences in treatment. Anti-NMO antibodies play a crucial role in the workup and diagnosis of NMOSD. In this review, Dr Elaine Au provided an overview of the NMOSD condition and the use of anti-NMO antibody assays. We welcome any feedback or suggestions. Please direct them to Dr Elaine Au (email: ayl436@ha.org.hk) of Education Committee, the Hong Kong College of Pathologists. Opinions expressed are those of the authors or named individuals, and are not necessarily those of the Hong Kong College of Pathologists. 

Dr Au Yuen Ling Elaine
Associate Consultant, Division of Clinical Immunology, Department of Pathology, Queen Mary Hospital 

 

NMO is an idiopathic immune mediated demyelinating disease that predominantly affects optic nerves and spinal cord. The prevalence range from 0.3 to 4.4 per 100000 people, with Asian and African-American more affected than Caucasian, where multiple sclerosis is more common in the white population (1-5). The condition has been named as Devic’s disease in the past (6), which described a monophasic disorder presenting with simultaneous bilateral optic neuritis and transverse myelitis. With the availability of specific serological marker, antibodies that targeted the water channel aquaporin-4 (AQP4), the clinical and neuroimaging spectrum of NMO disease is broadened. Instead of being a monophasic disorder, NMO antibodies positive patients with recurrent attacks are not uncommonly found. Moreover, the clinical presentations are more variable than the traditional Devic disease. There is no pathognomonic clinical feature of spectrum disorder (NMOSD), though certain clinical presentations are particularly suggestive of the disorder. These include simultaneously bilateral optic neuritis, complete spinal cord syndrome and area postrema clinical syndrome.

 

Multiple sclerosis is an important differential diagnosis of this condition in view of the overlapping clinical features of these two conditions. In NMOSD, optic neuritis tends to be more severe, more often with simultaneous bilateral involvement or sequential in rapid succession, compare to multiple sclerosis. Complete spinal cord syndrome, with longitudinally extensive transverse myelitis in MRI, is more suggestive of NMOSD than multiple sclerosis. Differentiating NMOSD from other demyelinating disease, i.e. multiple sclerosis is important since the treatment is different. Indeed, some multiple sclerosis therapies may aggravate NMO disorders (7-10).

 

Diagnostic Criteria

In 2006, the serological marker was first incorporated into the revised NMO diagnostic criteria. In 2007, NMOSD was introduced to include seropositive patients who do not follow the classical monophasic bilateral optic neuritis and transverse myelitis. Lately, the International Panel for NMO Diagnosis (IPND) has further revised the diagnostic criteria (11). For anti-NMO antibodies positive cases, presenting at least one core clinical characteristic of the disease is required for diagnosis. Core clinical characteristics include optic neuritis, acute myelitis, area postrema syndrome (episode of otherwise unexplained hiccups or nausea and vomiting), acute brainstem syndrome, narcolepsy or acute diencephalic syndrome with typical Magnetic Resonance Imaging (MRI) lesions and symptomatic cerebral syndrome with typical MRI lesions. On the other hand, more stringent clinical criteria, with additional neuroimaging findings, are required in seronegative patients to fulfill the diagnostic criteria (See appendix). 

For the workup of the disease, MRI, cerebral spinal fluid (CSF) exam and serological test for anti-NMO antibodies are important. In some patients, CSF pleocytosis, usually in the form of monocytosis and lymphocytosis, are present. Increased CSF protein levels are noted in 46-75% of cases (12, 13). Nevertheless, presence of CSF oligoclonal bands is uncommon in NMOSD, and at most transient, in contrast to the presence of persistent CSF oligoclonal bands in the case of multiple sclerosis. Finally, visual evoked potentials, somatosensory evoked potentials and brainstem acoustic evoked potentials examination may also be helpful in the workup.

 

Clinical course and prognosis

In NMOSD syndromes affecting regions other than optic nerve and spinal cord, not uncommonly patients will relapse with more classical involvement in subsequent attacks. Majority of NMOSD patients suffer from recurrent attacks (80- 90%), less frequently monophasic attack (10-20%) (14), while gradual progressive course with neurological deterioration is very rare (15). Relapses usually occur in clusters, but unpredictable intervals. In the Mayo Clinic series, the second relapse occurred within 1 year in 60% of cases, and within 3 years in 90% of cases (16). Repeated NMO attacks not uncommonly lead to accumulation of neurological impairment. NMO is associated with more adverse outcome than MS in general(14).

NMOSD has been shown to be frequently associated with other autoimmune disorders, including lupus, Sjogren’s syndrome, etc (17-19). On contrary, NMOSD is not common in rheumatic disease patients.

 

Anti-NMO antibodies

Among the different investigations, NMO antibodies test is central to the workup. Anti-NMO antibodies are pathogenic. The third extracellular loop of AQP4 is the major epitope for the anti- NMO antibodies. Biopsy and autopsy tissue obtained from seropositive patients demonstrate loss of AQP4 immunoreactivity. Perivascular complement activation in actively demyelinating lesions is also happened. In the central nervous system (CNS), AQP4 is expressed at the foot processes of astrocytes, near the basement membranes, in the optic nerve, in a subpopulation of ependymal cells, in hypothalamic nuclei and in the subfornical organ (20, 21). Truncated astrocyte processes or cell loss were found in demyelinating lesions (11). In rat models, passive transfer of the antibodies leaded to the development of disease (22, 23). These pathological findings distinguish NMOSD from multiple sclerosis.

The Anti-NMO antibodies can be detected by indirect immunofluorescence staining on tissue slide using mouse cerebellum tissue section, cell- based assays, radioimmunoprecipitation assays and enzyme-linked immunosorbent assays (ELISA). Overall, cell-based assay is preferred in view of better assay sensitivity and specificity compared to other methods. Ideally, confirmatory testing with one or more techniques is suggested (11), especially in cases with atypical presentation or borderline results are obtained.

In tissue based indirect immunofluorescence test, NMO antibodies positive case is characterized by the binding to structures adjacent to microvasculature, the Virchow-Robin spaces (VRS) and pia mater (Fig.1).

 

Fig. 1. Mouse cerebellum tissue section stained with anti-NMO antibodies.

 

This assay allows the detection of any coexisting anti-neuronal antibodies, which may be important as differential diagnosis and workup. However, the method is observer dependent and subjective. The interpretation of antibody staining may easily be affected by non-specific background staining on the tissue. In some rare occasions, antibodies other than anti-NMO may mimic the staining pattern and lead to false positive results. Moreover, indirect tissue based immunofluorescence test has relative low sensitivity (63-64%) (24-27).

Cell-based assay utilize cell lines such as human embryonic kidney 293 (HEK293) cells or Chinese hamster ovary (CHO) cells that have been transfected with AQP4 gene expression vector, so that expressing much higher level of antigen comparing to normal tissues. Cell lines from different units may use different ratio of the two isoform of AQP4: M1 and M23 in order to obtain optimal antigen presentation. Cell-based assay can be assessed by indirect immunofluorescence staining or flow cytometry. For indirect immunofluorescence cell- based assay, slide with fixed AQP-4 gene transfected cells and non- transfected cells growing on different biochips are placed side by side for comparison. Therefore, false positivity is minimized with the inclusion of control non-transfected cells. A higher expression of antigen in the transfected cells also enhance the assay sensitivity compared to tissue-based indirect immunofluorescence testing. (Fig.2)

 

Fig.2. HEK 293 cells transfected with AQP-4 gene expression vector and stained positive with anti- NMO antibodies.

 

Overall, cell-based assay is the recommended assay in view of good sensitivity and specificity (mean sensitivity 76.7% in a pooled analysis; 0.1% false positivity in a multiple sclerosis cohort) (24- 27). Commercial kits for indirect immunofluorescence cell-based assay are available, which facilitate the assay setup in service laboratories. Nevertheless, indirect immunofluorescence method is semi-quantitative and observer dependent.

Protein-based assays, like ELISA and radioimmunoprecipitation assays, in general, have lower sensitivity compared to cell based assays. In addition, ELISA, in particular at low titer, may yield nonspecific results. However, these assays provide quantitative results which may potentially be used for serial monitoring (24).

Though NMO antibody testing in serum is well- established, the diagnostic role of testing the antibody in CSF is controversial. Most of the cases reported in literature are diagnosed by serum test, though there have been rare cases reported that were CSF positive but serum test negative (28, 29). When studying paired CSF and serum samples with antibody indices calculated, intrathecal production of the NMO antibody is rare (24). NMO antibodies can be present in patients few years before and after the disease presentations. Lately, there is increasing evidence that the antibody titre may reflect disease activity. Elevated antibody levels at relapse and decrease in titre after immunosuppressant treatment has been reported in literature (30-34). Therefore, serial monitoring may possibly facilitate management and medication adjustment. However, there is no general threshold value for clinical relapse and the absolute level varies with individual patients. Rising level may not predict relapse in all cases. In addition, some methodologies, like indirect immunofluorescence test, only provide semi-quantitative results, and inter-run reproducibility is another issue. Other factors including the frequency of test necessary to achieve meaningful disease status monitoring and the cost involved are also important consideration. Therefore, it remains to be determined whether the marker should be serially monitored for treatment response and disease activity monitoring.

 

Treatment

The treatment for classical Devic’s disease presentation and relapsing NMOSD presentation is no different. High dose steroid is commonly employed as first- line of treatment in acute presentation. Plasma exchange may be considered in treatment refractory cases. Immunomodulatory treatment with interferon β, which is a treatment option in multiple sclerosis, may exacerbate NMOSD disorders. Therefore, differentiating between these two conditions is important. Options of steroid sparing immunosuppressants to consider in NMOSD include azathioprine, methotrexate, mycophenolate mofetil, rituximab, etc (14).

 

Conclusion

NMOSD is a rare but increasingly recognized condition, which present as an inflammatory and demyelinating autoimmune disorder affecting the central nervous system. With the availability of a serological marker, anti-NMO antibody, the diagnosis and differentiating from related conditions is facilitated. Timely diagnosis and treatment is important for the management of these patients.

 

Reference

1. Kira J. Multiple sclerosis in the Japanese population. The Lancet Neurology. 2003;2(2):117- 27.

2. abre P, Signate A, Olindo S, Merle H, Caparros-Lefebvre D, Bera O, et al. Role of return migration in the emergence of multiple sclerosis in the French West Indies. Brain : a journal of neurology. 2005;128(Pt 12):2899-910.

3. Asgari N, Lillevang ST, Skejoe HP, Falah M, Stenager E, Kyvik KO. A population-based study of neuromyelitis optica in Caucasians. Neurology. 2011;76(18):1589-95.

4. Cossburn M, Tackley G, Baker K, Ingram G, Burtonwood M, Malik G, et al. The prevalence of neuromyelitis optica in South East Wales. European journal of neurology. 2012;19(4):655-9.

5. Mealy MA, Wingerchuk DM, Greenberg BM, Levy M. Epidemiology of neuromyelitis optica in the United States: a multicenter analysis. Archives of neurology. 2012;69(9):1176-80.

6. Jarius S, Wildemann B. The history of neuromyelitis optica. Journal of neuroinflammation. 2013;10:8.

7. Kimbrough DJ, Fujihara K, Jacob A, Lana- Peixoto MA, Leite MI, Levy M, et al. Treatment of Neuromyelitis Optica: Review and Recommendations. Multiple sclerosis and related disorders. 2012;1(4):180-7.

8. Kleiter I, Hellwig K, Berthele A, Kumpfel T, Linker RA, Hartung HP, et al. Failure of natalizumab to prevent relapses in neuromyelitis optica. Archives of neurology. 2012;69(2):239-45.

9. Min JH, Kim BJ, Lee KH. Development of extensive brain lesions following fingolimod (FTY720) treatment in a patient with neuromyelitis optica spectrum disorder. Multiple sclerosis. 2012;18(1):113-5.

10. Papeix C, Vidal JS, de Seze J,Pierrot- Deseilligny C, Tourbah A, Stankoff B, et al. Immunosuppressive therapy is more effective than interferon in neuromyelitis optica. Multiple sclerosis. 2007;13(2):256-9.

11. Wingerchuk DM, Banwell B, Bennett JL, Cabre P, Carroll W, Chitnis T, et al. International consensus diagnostic criteria for neuromyelitis optica spectrum disorders. Neurology. 2015;85(2):177-89.

12. O'Riordan JI, Gallagher HL, Thompson AJ, Howard RS, Kingsley DP, Thompson EJ, et al. Clinical, CSF, and MRI findings in Devic's neuromyelitis optica. Journal of neurology, neurosurgery, and psychiatry. 1996;60(4):382-7.

13. de Seze J, Stojkovic T, Ferriby D, Gauvrit JY, Montagne C, Mounier-Vehier F, et al. Devic's neuromyelitis optica: clinical, laboratory, MRI and outcome profile. Journal of the neurological sciences. 2002;197(1-2):57-61.

14. Sellner J, Boggild M, Clanet M, Hintzen RQ, Illes Z, Montalban X, et al. EFNS guidelines on diagnosis and management of neuromyelitis optica. European journal of neurology. 2010;17(8):1019-32.

15. Wingerchuk DM, Pittock SJ, Lucchinetti CF, Lennon VA, Weinshenker BG. A secondary progressive clinical course is uncommon in neuromyelitis optica. Neurology. 2007;68(8):603-5.

16. Wingerchuk DM, Hogancamp WF, O'Brien PC, Weinshenker BG. The clinical course of neuromyelitis optica (Devic's syndrome). Neurology. 1999;53(5):1107-14.

17. Jarius S, Jacobi C, de Seze J, Zephir H, Paul F, Franciotta D, et al. Frequency and syndrome specificity of antibodies to aquaporin-4 in neurological patients with rheumatic disorders. Multiple sclerosis. 2011;17(9):1067-73.

18. Pittock SJ, Lennon VA, de Seze J, Vermersch P, Homburger HA, Wingerchuk DM, et al. Neuromyelitis optica and non organ-specific autoimmunity. Archives of neurology. 2008;65(1):78-83.

19. Wandinger KP, Stangel M, Witte T, Venables P, Charles P, Jarius S, et al. Autoantibodies against aquaporin-4 in patients with neuropsychiatric systemic lupus erythematosus and primary Sjogren's syndrome. Arthritis and rheumatism. 2010;62(4):1198-200.

20. Graber DJ, Levy M, Kerr D, Wade WF. Neuromyelitis optica pathogenesis and aquaporin 4. Journal of neuroinflammation. 2008;5:22.

21. Tait MJ, Saadoun S, Bell BA, Papadopoulos MC. Water movements in the brain: role of aquaporins. Trends in neurosciences. 2008;31(1):37-43.

22. Kinoshita M, Nakatsuji Y, Moriya M, Okuno T, Kumanogoh A, Nakano M, et al. Astrocytic necrosis is induced by anti-aquaporin-4 antibody- positive serum. Neuroreport. 2009;20(5):508-12.

23. Kinoshita M, Nakatsuji Y, Kimura T, Moriya M, Takata K, Okuno T, et al. Neuromyelitis optica: Passive transfer to rats by human immunoglobulin. Biochemical and biophysical research communications. 2009;386(4):623-7.

24. Jarius S, Wildemann B. Aquaporin-4 antibodies (NMO-IgG) as a serological marker of neuromyelitis optica: a critical review of the literature. Brain pathology. 2013;23(6):661-83.

25. Waters PJ, McKeon A, Leite MI, Rajasekharan S, Lennon VA, Villalobos A, et al. Serologic diagnosis of NMO: a multicenter comparison of aquaporin-4-IgG assays. Neurology. 2012;78(9):665-71; discussion 9.

26. Sato DK, Nakashima I, Takahashi T, Misu T, Waters P, Kuroda H, et al. Aquaporin-4 antibody- positive cases beyond current diagnostic criteria for NMO spectrum disorders. Neurology. 2013;80(24):2210-6.

27. Pittock SJ, Lennon VA, Bakshi N, Shen L, McKeon A, Quach H, et al. Seroprevalence of aquaporin-4-IgG in a northern California population representative cohort of multiple sclerosis. JAMA neurology. 2014;71(11):1433-6.

28. Klawiter EC, Alvarez E, 3rd, Xu J, Paciorkowski AR, Zhu L, Parks BJ, et al. NMO-IgG detected in CSF in seronegative neuromyelitis optica. Neurology. 2009;72(12):1101-3.

29. Long Y, Qiu W, Lu Z, Peng F, Hu X. Clinical features of Chinese patients with multiple sclerosis with aquaporin-4 antibodies in cerebrospinal fluid but not serum. Journal of clinical neuroscience : official journal of the Neurosurgical Society of Australasia. 2013;20(2):233-7.

30. Jarius S, Aboul-Enein F, Waters P, Kuenz B, Hauser A, Berger T, et al. Antibody to aquaporin-4 in the long-term course of neuromyelitis optica. Brain : a journal of neurology. 2008;131(Pt 11):3072-80.

31. Jarius S, Franciotta D, Paul F, Ruprecht K, Bergamaschi R, Rommer PS, et al. Cerebrospinal fluid antibodies to aquaporin-4 in neuromyelitis optica and related disorders: frequency, origin, and diagnostic relevance. Journal of neuroinflammation. 2010;7:52.

32. Jarius S, Franciotta D, Paul F, Bergamaschi R, Rommer PS, Ruprecht K, et al. Testing for antibodies to human aquaporin-4 by ELISA: sensitivity, specificity, and direct comparison with immunohistochemistry. Journal of the neurological sciences. 2012;320(1-2):32-7.

33. Kim W, Lee JE, Li XF, Kim SH, Han BG, Lee BI, et al. Quantitative measurement of anti- aquaporin-4 antibodies by enzyme-linked immunosorbent assay using purified recombinant human aquaporin-4. Multiple sclerosis. 2012;18(5):578-86.

34. Takahashi T, Fujihara K, Nakashima I, Misu T, Miyazawa I, Nakamura M, et al. Anti-aquaporin- 4 antibody is involved in the pathogenesis of NMO: a study on antibody titre. Brain : a journal of neurology. 2007;130(Pt 5):1235-43.

 

Appendix

NMOSD diagnostic criteria for adult patients

---

Diagnostic criteria for NMOSD with NMO-IgG

1. At least 1 core clinical characteristic

2. Positive test for NMO-IgG using best available detection method (cell-based assay strongly recommended)

3. Exclusion of alternative diagnoses

---

Diagnostic criteria for NMOSD without NMO-IgG or NMOSD with unknown NMO-IgG status

1. At least 2 core clinical characteristics occurring as a result of one or more clinical attacks and meeting all of the following requirements:

   - At least 1 core clinical characteristic must be optic neuritis , acute myelitis with LETM, or area postrema syndrome

   - Dissemination in space (2 or more different core clinical characteristics)

   - Fulfillment of additional MRI requirements, as applicable

2. Negative tests for NMO-IgG using best available detection method, or testing unavailable

3. Exclusion of alternative diagnoses

---

Core clinical characteristics

1. Optic neuritis

2. Acute myelitis

3. Area postrema syndrome: episode of otherwise unexplained hiccups or nausea and vomiting

4. Acute brainstem syndrome

5. Symptomatic narcolepsy or acute diencephalic clinical syndrome with NMOSD-typical diencephalic MRI lesions

6. Symptomatic cerebral syndrome with NMOSD-typical brain lesions

---

Additional MRI requirements for NMOSD without NMO-IgG and NMOSD with unknown NMO-Ig status

1. Acute optic neuritis: require brain MRI showing (a) normal findings or only nonspecific white matter lesions, OR (b) optic nerve MRI with T2-hyperintense lesion or T1-weighted gadolinium-enhancing lesion extending over >1/2 optic nerve length or involving optic chiasm

2. Acute myelitis: requires associated intramedullary MRI lesion extending over >=3 contiguous segments (LETM) OR >=3 contiguous segments of focal spinal cord atrophy in patients with history compatible with acute myelitis

3. Area postrema syndrome: requires associated dorsal medulla/ area postrema lesions 4. Acute brainstem syndrome: requires associated periependymal brainstem lesions

---

Neurology 2015;85:177-189

 

Clinical features and laboratory findings atypical for NMOSD, that need to consider alternative diagnoses

---

1. Progressive overall clinical course (neurologic deterioration unrelated to attacks: Consider MS)

2. Atypical time to attack nadir: less than 4 hours (consider cord ischemia/ infarction); continual worsening for more than 4 weeks from attack onset (consider sarcoidosis or neoplasm)

3. Partial transverse myelitis, especially when not associated with LETM MRI lesion (consider MS)

4. Presence of CSF oligoclonal bands (oligoclonal bands occur in < 20% of cases of NMO vs > 80% of MS

---

Comorbidities associated with neurologic syndromes that mimic NMOSD

1. Sarcoidosis, established or suggestive clinical, radiologic or laboratory findings thereof (e.g. mediastinal adenopathy, fever and night sweats, elevated serum angiotensin converting enzyme or interleukin-2 receptor level)

2. Cancer, established or with suggestive clinical, radiologic or laboratory findings thereof; consider lymphoma or paraneoplastic disease ( e.g. collapsing response mediator protein-5 associated optic neuropathy and myelopathy or anti-Ma- associated diencephalic syndrome)

3. Chronic infection, established or with suggestive clinical radiologic, or laboratory findings thereof ( e.g. HIV, syphilis)

---

Neurology 2015;85:177-189

Results of College Exam 2017 (Council Meeting 26 September 2017)

 

Fellowship Assessment:

 

Exam No.	Result
E17201	PASS
E17202	PASS
E17203	PASS
E17204	PASS
E17205	FAIL
E17206	FAIL
E17207	FAIL
E17208	PASS
E17209	PASS
E17210	FAIL
E17211	FAIL
E17212	FAIL
E17213	PASS
E17214	PASS
E17215	FAIL

 

Membership Examination:

 

Exam No.	Result
E17101	PASS
E17102	PASS
E17103	PASS
E17104	FAIL
E17105	FAIL
E17106	PASS
E17107	PASS
E17108	PASS
E17109	FAIL

 

Molecular alterations of gastrointestinal stromal tumor - Prognostic and therapeutic implications 

 

Volume 12, Issue 2 August 2017  (download full article in pdf)

 

Editorial note:

Gastrointestinal stromal tumor is the commonest mesenchymal tumor in the digestive system. It is a genetically heterogeneous disease with various mutations apart from classical activation mutations in KIT  and PDGFRA genes. In the topical update, Dr. Anthony Chan provided an overview of molecular alterations of gastrointestinal stromal tumor with emphasis on their prognostic and therapeutic significance. We welcome any feedback or suggestions. Please direct them to Dr. Anthony Chan (e-mail: awh_chan@cuhk.edu.hk) of Education Committee, the Hong Kong College of Pathologists. Opinions expressed are those of the authors or named individuals, and are not necessarily those of the Hong Kong College of Pathologists. 

Dr. Anthony W.H. Chan
Clinical Associate Professor
Department of Anatomical and Cellular Pathology, Prince of Wales Hospital, The Chinese University of Hong Kong 

 

The gist of GIST

Gastrointestinal stromal tumor (GIST) is a rare tumor with the annual incidence rate of 10- 15/1,000,000, but it is the commonest mesenchymal tumor in the digestive system. It affects both sexes equally and presents at any age from children to elderly with the median age of mid 60s. Stomach (55.6%) is the most frequent primary tumor site followed by small intestine (31.8%), large intestine (6.0%) and esophagus (0.7%). Other uncommon primary sites, such as omentum, mesentery and liver, accounts for 5.5% of all GISTs.(1) Important milestones of GIST in diagnostic, prognostic and therapeutic aspects are briefly summarized in this section. 

In the past, GIST was regarded as leiomyoma, leiomyoblastoma or leiomyosarcoma before the era of wide availability of immunohistochemistry. In 1983, Mazur and Clark first applied the term "stromal tumor" to describe a group of gastric mesenchymal tumor lacking ultrastructural features of smooth muscle or schwann cells.(2) In 1989, a short-lived term, gastrointestinal autonomic nerve tumor (GANT), was used to describe a small subset of GIST featured by small intestinal location, epithelioid appearance and focal immunoreactivity towards neural markers (S100, neurofilament and synaptophysin).(3) In 1995, CD34 was found to be the first useful diagnostic immunohistochemical marker to differentiate GIST from leiomyoma and schwannoma although only 60-70% of all GISTs are immunoreactive to CD34.(4) In 1998, the hallmark constitutive activation mutation of KIT gene and overexpression of KIT/CD117 protein in GIST were discovered by Hirota et al.(5) This finding also suggested that GIST may be originated from interstitial cells of Cajal, pacemaker cells of intestine, which express KIT and CD34. However, activation mutation of KIT gene and overexpression of KIT are not consistently correlated. A subset of KIT positive GISTs was found to lack KIT mutation and this observation led to the subsequent discovery of gain-of-function mutation of platelet-derived growth factor receptor alpha (PDGFRA) gene in 2003.(6, 7) KIT and PDGFRA mutations are mutually exclusive. About 5-10% of GISTs, particularly those with PDGFRA mutation do not express KIT. In 2004, West et al. identified a novel gene, DOG1 (discovered on GIST-1), through cDNA microarray, and showed DOG1 protein was highly expressed in GISTs (97.8%), including those KIT negative GISTs.(8) KIT and/or DOG1 become crucial diagnostic immunohistochemical markers for GIST. A small subgroup of GISTs with immunoreactivity of KIT/DOG1 lack neither KIT or PDGFRA mutation was first designated as wild-type GISTs in the same year.(9) Wild-type GISTs are later shown to be a heterogeneous group with various mutations.(10- 13)

Prognosis of patients with GIST is shown to be correlated with tumor size and mitosis. The first consensus risk stratification was proposed by investigators in National Institutes of Health (NIH) in 2002 (Table 1).(14) Anatomical location of GIST is also an important prognostic factor and firstly integrated to the Armed Forces Institute of Pathology system in 2006 (Table 2)(15). Gastric GIST behaves more indolent than small and large bowel GIST with similar size and mitosis. Tumor rupture is an additional prognosticator for GIST patients and incorporated into the modified NIH system in 2008 (Table 3).(16) Finally, the most widely adopted tumor staging system, American Joint Committee on Cancer (AJCC), include GIST risk stratification composed of tumor size, mitosis, anatomical location, nodal and distant metastases in the 7th edition in 2010, which remains unchanged in the recently released 8th edition (Table 4 and 5).

Surgical resection remains the mainstay of curative therapy for GIST but a substantial portion of GIST patients present in advanced stage beyond surgical intervention. Imatinib, a multi-targeted tyrosine kinase inhibitor specific for c-abl, c-kit and PDGFR, was first used in a patient with metastatic GIST in 2001.(17) The dramatic clinical response from this patient and the subsequent successful phase II clinical trial in 2002 secured the first-line role of imatinib for patients with inoperable GIST and pioneered molecular targeted therapy for sarcoma.(18) Primary and acquired resistance to imatinib among GIST patients led to development of newer targeted agents. Two hallmark phase III randomized controlled trials on sunitinib (NCT00075218) and regorafenib (NCT01271712) for GIST were completed in 2006 and 2013, respectively.(19, 20) Sunitinib and regorafenib are indicated for patients with advanced GIST resistant or intolerant to imatinib. 

 

Table 1: NIH risk stratification for GIST (14) 

GROUP	SIZE (CM)	MITOSIS (/50 HPF)
Very low risk	<2	≤5
Low risk	2-5	≤5
Intermediate risk	<5	6-10
	5-10	≤5
High risk	>5	>5
	>10	Any
	Any	>10

 

Table 2: AFIP risk stratification for GIST (15) 

GROUP	SIZE (CM)	MITOSIS (/50 HPF)	STOMACH	DUODENUM	JEJUNUM /ILEUM	RECTUM
1	≤2	≤5	None	None	None	None
2	>2-5	≤5	Very low	Low	Low	Low
3a	>5-10	≤5	Low	Moderate	-	-
3b	>10	≤5	Moderate	High	High	High
4	≤2	>5	None	High	-	High
5	>2-5	>5	Moderate	High	High	High
6a	>5-10	>5	High	High	-	-
6b	>10	>5	High	High	High	High

 

Table 3: Modified NIH risk stratification for GIST (16) 

GROUP	SIZE (CM)	MITOSIS (/50 HPF)	PRIMARY SITE
Very low risk	≤2	≤5	Any
Low risk	>2-5	≤5	Any
Intermediate Risk	>2-5	>5	Gastric
	≤5	6-10	Any
	>5-10	≤5	Gastric
High risk	>5	>5	Any
	>10	Any	Any
	Any	>10	Any
	Any	Any	Tumor rupture
	>2-5	>5	Non-gastric
	>5-10	≤5	Non-gastric

 

Table 4: AJCC staging system for gastric and omental GIST 

GROUP	SIZE (CM)	N	M	MITOSIS
IA	≤5	0	0	≤5
IB	>5-10	0	0	≤5
II	≤5	0	0	>5
	>10	0	0	≤5
IIIA	>5-10	0	0	>5
IIIB	>10	0	0	>5
IV	Any	1	0	Any
	Any	Any	1	Any

 

Table 5: AJCC staging system for small/large bowel, esophageal, mesenteric and peritoneal GIST 

GROUP	SIZE (CM)	N	M	MITOSIS
I	≤5	0	0	≤5
II	>5-10	0	0	≤5
IIIA	≤2	0	0	>5
	>10	0	0	≤5
IIIB	>2	0	0	>5
IV	Any	1	0	Any
	Any	Any	1	Any

 

 

Mutational landscape of GIST

KIT and PDGFRA mutations are major driver mutations in GIST tumorigenesis. Both genes encode type III receptor tyrosine kinases with similar structures: extracellular ligand binding domain and dimerization domain, a transmembrane sequence, a juxtamembrane domain and intracellular kinase domain (Figure 1). Binding of corresponding ligands, stem cell factor and PDGFA, to c-kit and PDGFRA receptor, respectively, dimerizes and activates receptor tyrosine kinases. In GIST, activation mutations in KIT and PDGFRA lead to uncontrolled ligand- independent receptor activation. Mutation hotspots of KIT gene are located at exons 9, 11, 13 and 17, whereas those of PDGFRA gene are situated at exons 12, 14 and 18. Mutation of extracellular domain of KIT encoded by exon 9 facilitate receptor dimerization. Mutations in the juxtamembrane domain, which is encoded by exon 11 of KIT and exon 12 of PDGFRA, allow dimerization of receptor without binding of ligands. Mutations of ATP binding region of kinase domain (encoded by exon 13 of KIT and exon 14 of PDGFRA) enhance kinase activity, while mutations of activation loop (encoded by exon 17 of KIT and exon 18 of PDGFRA) promote active conformation of kinase.(21) Table 6 and Figure 2 summarize the mutational landscape of GIST based on the data from population-based studies and clinical trials.(22-29) Frequencies of PDGFRA mutations are significantly lower among patients in clinical trials (mean 1.7%) than those in population-based studies (mean 14.9%) because GIST patients with PDGFRA mutations are associated with better prognosis and earlier stage and hence do not require systemic therapy.(9, 22, 23, 29)

KIT mutation accounts for 71.5% (64.8-89.1%) of mutations in GISTs.(24, 25, 27-29) Exon 11 mutation is the commonest mutation (61.1%, range: 56.1-77.1%). Deletion, substitution and duplication contribute to 23-28%, 2-20% and 2-7%, respectively. Deletion in exon 11 is associated with younger age, larger tumor size, higher mitotic count and poor prognosis, whereas duplication is associated with female and stomach predilection and better prognosis. Exon 9 mutation is found in 7.1-10.9% of GISTs, particularly in those arising from small and large intestine, and associated with poor prognosis. Exon 13 and exon 17 are rare mutation hotspots (<1-2%) in GISTs, which are almost exclusively spindle in morphology and more frequently developed in small intestine. GISTs with exon 13 and 17 mutants are associated good and intermediate prognosis, respectively.

PDGFRA mutation accounts for 14.9% (4.7-21.1%) of mutations in GISTs.(24, 25, 27-29) About 30- 40% of GISTs without immunoreactivity of KIT/CD117 harbour PDGFRA mutation. GISTs with PDGFRA mutation generally show predilection to gastric location (>90%) and epithelioid/mixed morphology, and favourable prognosis (except non-D842V exon 18 mutation).

Wild-type GIST, which express immunoreactivity of KIT/DOG1 but lack neither KIT or PDGFRA mutation, contributes to 13-18% of adult GISTs and 85% of pediatric GIST.(10-12) As previously mentioned, it is a genetically heterogeneous group (Figure 3). Wild-type GIST can be further stratified by using succinate dehydrogenase B (SDHB) immunohistochemistry and familial syndromes. On one hand, SDHB deficient wild-type GISTs accounts for about 5% of all GISTs, and can be sporadic or related to Carney triad and Carney- Stratakis syndrome. Carney triad is a constellation of GIST, paraganglioma and pulmonary chondroma with undetermined germline mutation, whereas Carney-Stratakis syndrome is an autosomal dominant disease with dyad of GIST and paraganglioma, and germline mutations in SDHB, SDHC or SDHD genes.(30) SDHB deficient wild-type GISTs are featured by female predominance (except for Carney-Stratakis syndrome), exclusive location in stomach, multifocality, epithelioid/mixed morphology, unpredictable clinical outcome by histology, indolent clinical course despite frequent nodal metastasis, and mutation id SDH subunits (except for Carney triad). On the other hand, SDHB proficient wild-type GISTs make up 10.5% of all GISTs, and are either sporadic (9%) or syndromic (1.5%). Syndromic SDHB proficient wild-type GISTs are associated with neurofibromatosis type 1, absence of sex/age predilection, small intestine in location, multifocality, spindle morphology, and favorable prognosis. Sporadic SDHB proficient wild-type GISTs can be further classified according to BRAF mutation. Sporadic SDHB proficient wild-type GISTs with BRAF mutation usually occur in 6th decade of age and small intestine with spindle morphology. Prognosis of this subgroup is inconclusive.(10, 29, 31, 32) Sporadic SDHB proficient wild-type GISTs without BRAF mutation are also known as quadruple wild-type GISTs without any mutation in KIT, PDGFRA, SDH and genes in RAS pathway (BRAF/NF1).(12, 13) They represent the commonest subgroup (7%) of wild-type GISTs and a genetically heterogeneous subgroup harboring ETV6-NTRK3 translocation, FGFR1-TACC1 translocation, mutation of MEN1 and MAX, and overexpression of COL22A1 and CALCRL.(12, 29, 33, 34) Due to complex genetic heterogeneity, clinicopathological features of this subgroup have not been well characterized.

 

Figure 1: Schematic diagram of the structures of KIT and PDGFRA receptor tyrosine kinases 

 

Figure 2: Mutational landscape of GIST 

 

Figure 3: Classification of wild-type GIST 

 

Table 6: Mutational landscape of GIST

Study	Region	n	KIT exon				PDGFRA exon			Wild type
			9	11	13	17	12	14h	18
Wozniak 2012 (24)	Poland	427	7.3%	61.1%	0.5%	0.5%	0.2%	0.7%	11.9%	17.8%
Wozniak 2014 (28)	Europe	1056	7.4%	61.4%	1.8%	0.6%	0.9%	0.3%	12.8%	14.9%
Künstlinger 2013 (25)	Germany	1366	9.2%	59.3%	1.8%	0.8%	1.8%	0.6%	13.8%	12.7%
Wang 2014 (27)	China	275	10.9%	77.1%	1.1%	0.0%	1.1%	0.0%	3.6%	6.2%
Rossi 2015 (29)	Italy	451	7.1%	56.1%	0.9%	0.7%	2.2%	1.6%	17.3%	14.2%
ACOSOG Z9001 (26)		507	6.9%	67.3%	1.8%	0.2%	NA	NA	NA	12.8%
CALGB 150105 (23)		378	8.2%	72.8%	0.8%	1.1%	0.0%	0.0%	1.6%	15.3%
EORTC 62005 (22)		377	15.4%	65.8%	1.6%	0.8%	0.8%	0.0%	1.9%	13.8%

 

 

Clinical implications of mutations in GIST

Different mutations in GIST have their own characteristic prognostic and therapeutic implications. Prognostic significance of individual mutations have been described by various investigators and briefly mentioned in the previous section. Rossi et al. recently systemically analyzed the prognostic impact of mutations among 451 patients with primary localized treatment-naive GISTs.(29) By multivariable Cox regression, mutational status was an independent prognosticator in addition to patient's age, tumor location, tumor size and mitotic count. Three molecular risk groups with prognostic significance were identified: Group 1 with the most favorable outcome is composed of mutations in KIT exon 13, PDGFRA exon 12 and BRAF; Group 2 with the intermediate outcome (hazard ratio 3.06) consists of KIT/PDGFRA/BRAF triple negative, and mutations in KIT exon 17, PDGFA exon 14 and 18 (D842V); and Group 3 with the most unfavorable outcome comprises mutations in KIT exon 9 and 11, and PDGFRA exon 18 (non-D842V).

Clinical response toward imatinib among GIST patients is closely related to tumor genotype. In a phase III clinical trial (SWOG S0033/CALGB 150105), the investigators demonstrated that patients with KIT exon 11 mutation (complete response [CR]/partial response [PR] 71.7%) had better response to imatinib than those with KIT exon 9 mutation (CR/PR 44.4%) and wild-type KIT (CR/PR 44.6%).(23) They also showed that doubling the dose of imatinib (from 400 mg to 800 mg) improved response rates for patients with exon 9-mutant tumors (CR/PR 17% vs. 67%). Double dose of imatinib did not offer any better response rate among patients with exon 11 mutant or wild- type KIT. A subsequent meta-analysis of 1,640 patients with advanced GIST receiving imatinib confirmed that double dose of imatinib improved progression-free survival and objective response rate, but not overall survival, among patients with KIT exon 9-mutant GIST.(35) PDGFA exon 18 (D842V) mutation and KIT/PDGFRA wild-type are responsible for primary resistance to imatinib.(36) Among patients with advanced GIST receiving imatinib, a substantial proportion of initial responders will develop acquired resistance. Secondary mutations in exon 11 (L576P and V559A), exon 13 (V654A), exon 14 (T670I), exon 17 and exon 18 (A829P) of KIT, and exon 18 of PDGFRA are related to acquired resistance to imatinib.(36)

Clinical response to sunitinib, the second line targeted therapy after imatinib failure, is also considerably affected by primary and acquired mutations of KIT. Patients with primary KIT exon 9 mutation or wild-type KIT had better overall and progression-free survival than those with KIT exon 11 mutation, whereas patients with acquired KIT exons 13 or 14 mutations had better outcome than those with KIT exon 17 or 18 mutations.(37) Similarly, clinical response to regorafenib, the third line therapy after imatinib and sunitinib failure, is significantly influenced by tumor genotype. Regorafenib provided better clinical outcome among patients with primary KIT exon 11 mutation and SDHB deficient GIST, (38) as well as those with secondary mutation of KIT exon 17, which are resistant to both imatinib and sunitinib.(39)

 

Summary

GIST is a genetically heterogeneous tumor. Genotypes and phenotypes are closely interrelated. Specific mutations have their characteristic clinicopathological features, prognostication and therapeutic implications. Genetic analyses KIT and PDGFRA are highly recommended especially among patients with advanced diseases undergoing targeted therapy. Wild-type GISTs are recommended to be further analysed by SDHB immunohistochemistry and BRAF mutation test. 

 

Reference

1. Soreide K, Sandvik OM, Soreide JA, Giljaca V, Jureckova A, Bulusu VR. Global epidemiology of gastrointestinal stromal tumours (GIST): A systematic review of population-based cohort studies. Cancer Epidemiol. 2016;40:39-46.

2. Mazur MT, Clark HB. Gastric stromal tumors. Reappraisal of histogenesis. Am J Surg Pathol. 1983;7(6):507-19.

3. Herrera GA, Cerezo L, Jones JE, Sack J, Grizzle WE, Pollack WJ, et al. Gastrointestinal autonomic nerve tumors. 'Plexosarcomas'. Arch Pathol Lab Med. 1989;113(8):846-53.

4. Miettinen M, Virolainen M, Maarit Sarlomo R. Gastrointestinal stromal tumors--value of CD34 antigen in their identification and separation from true leiomyomas and schwannomas. Am J Surg Pathol. 1995;19(2):207- 16.

5. Hirota S, Isozaki K, Moriyama Y, Hashimoto K, Nishida T, Ishiguro S, et al. Gain- of-function mutations of c-kit in human gastrointestinal stromal tumors. Science. 1998;279(5350):577-80.

6. Heinrich MC, Corless CL, Duensing A, McGreevey L, Chen CJ, Joseph N, et al. PDGFRA activating mutations in gastrointestinal stromal tumors. Science. 2003;299(5607):708-10.

7. Hirota S, Ohashi A, Nishida T, Isozaki K, Kinoshita K, Shinomura Y, et al. Gain-of-function mutations of platelet-derived growth factor receptor alpha gene in gastrointestinal stromal tumors. Gastroenterology. 2003;125(3):660-7.

8. West RB, Corless CL, Chen X, Rubin BP, Subramanian S, Montgomery K, et al. The novel marker, DOG1, is expressed ubiquitously in gastrointestinal stromal tumors irrespective of KIT or PDGFRA mutation status. Am J Pathol. 2004;165(1):107-13.

9. Corless CL, Fletcher JA, Heinrich MC. Biology of gastrointestinal stromal tumors. J Clin Oncol. 2004;22(18):3813-25.

10. Agaram NP, Wong GC, Guo T, Maki RG, Singer S, Dematteo RP, et al. Novel V600E BRAF mutations in imatinib-naive and imatinib-resistant gastrointestinal stromal tumors. Genes Chromosomes Cancer. 2008;47(10):853-9.

11. Janeway KA, Kim SY, Lodish M, Nose V, Rustin P, Gaal J, et al. Defects in succinate dehydrogenase in gastrointestinal stromal tumors lacking KIT and PDGFRA mutations. Proc Natl Acad Sci U S A. 2011;108(1):314-8.

12. Nannini M, Astolfi A, Urbini M, Indio V, Santini D, Heinrich MC, et al. Integrated genomic study of quadruple-WT GIST (KIT/PDGFRA/SDH/RAS pathway wild-type GIST). BMC Cancer. 2014;14:685.

13. Pantaleo MA, Urbini M, Indio V, Ravegnini G, Nannini M, De Luca M, et al. Genome-Wide Analysis Identifies MEN1 and MAX Mutations and a Neuroendocrine-Like Molecular Heterogeneity in Quadruple WT GIST. Mol Cancer Res. 2017;15(5):553-62.

14. Fletcher CD, Berman JJ, Corless C, Gorstein F, Lasota J, Longley BJ, et al. Diagnosis of gastrointestinal stromal tumors: A consensus approach. Hum Pathol. 2002;33(5):459-65.

15. Miettinen M, Lasota J. Gastrointestinal stromal tumors: pathology and prognosis at different sites. Semin Diagn Pathol. 2006;23(2):70-83.

16. Joensuu H. Risk stratification of patients diagnosed with gastrointestinal stromal tumor. Hum Pathol. 2008;39(10):1411-9.

17. Joensuu H, Roberts PJ, Sarlomo-Rikala M, Andersson LC, Tervahartiala P, Tuveson D, et al. Effect of the tyrosine kinase inhibitor STI571 in a patient with a metastatic gastrointestinal stromal tumor. N Engl J Med. 2001;344(14):1052-6.

18. Demetri GD, von Mehren M, Blanke CD, Van den Abbeele AD, Eisenberg B, Roberts PJ, et al. Efficacy and safety of imatinib mesylate in advanced gastrointestinal stromal tumors. N Engl J Med. 2002;347(7):472-80.

19. Demetri GD, van Oosterom AT, Garrett CR, Blackstein ME, Shah MH, Verweij J, et al. Efficacy and safety of sunitinib in patients with advanced gastrointestinal stromal tumour after failure of imatinib: a randomised controlled trial. Lancet. 2006;368(9544):1329-38. 

20. Demetri GD, Reichardt P, Kang YK, Blay JY, Rutkowski P, Gelderblom H, et al. Efficacy and safety of regorafenib for advanced gastrointestinal stromal tumours after failure of imatinib and sunitinib (GRID): an international, multicentre, randomised, placebo-controlled, phase 3 trial. Lancet. 2013;381(9863):295-302.

21. Corless CL, Barnett CM, Heinrich MC. Gastrointestinal stromal tumours: origin and molecular oncology. Nat Rev Cancer. 2011;11(12):865-78.

22. Debiec-Rychter M, Sciot R, Le Cesne A, Schlemmer M, Hohenberger P, van Oosterom AT, et al. KIT mutations and dose selection for imatinib in patients with advanced gastrointestinal stromal tumours. Eur J Cancer. 2006;42(8):1093- 103.

23. Heinrich MC, Owzar K, Corless CL, Hollis D, Borden EC, Fletcher CD, et al. Correlation of kinase genotype and clinical outcome in the North American Intergroup Phase III Trial of imatinib mesylate for treatment of advanced gastrointestinal stromal tumor: CALGB 150105 Study by Cancer and Leukemia Group B and Southwest Oncology Group. J Clin Oncol. 2008;26(33):5360-7.

24. Wozniak A, Rutkowski P, Piskorz A, Ciwoniuk M, Osuch C, Bylina E, et al. Prognostic value of KIT/PDGFRA mutations in gastrointestinal stromal tumours (GIST): Polish Clinical GIST Registry experience. Ann Oncol. 2012;23(2):353-60.

25. Kunstlinger H, Huss S, Merkelbach-Bruse S, Binot E, Kleine MA, Loeser H, et al. Gastrointestinal stromal tumors with KIT exon 9 mutations: Update on genotype-phenotype correlation and validation of a high-resolution melting assay for mutational testing. Am J Surg Pathol. 2013;37(11):1648-59.

26. Corless CL, Ballman KV, Antonescu CR, Kolesnikova V, Maki RG, Pisters PW, et al. Pathologic and molecular features correlate with long-term outcome after adjuvant therapy of resected primary GI stromal tumor: the ACOSOG Z9001 trial. J Clin Oncol. 2014;32(15):1563-70.

27. Wang M, Xu J, Zhao W, Tu L, Qiu W, Wang C, et al. Prognostic value of mutational characteristics in gastrointestinal stromal tumors: a single-center experience in 275 cases. Med Oncol. 2014;31(1):819.

28. Wozniak A, Rutkowski P, Schoffski P, Ray-Coquard I, Hostein I, Schildhaus HU, et al. Tumor genotype is an independent prognostic factor in primary gastrointestinal stromal tumors of gastric origin: a european multicenter analysis based on ConticaGIST. Clin Cancer Res. 2014;20(23):6105-16.

29. Rossi S, Gasparotto D, Miceli R, Toffolatti L, Gallina G, Scaramel E, et al. KIT, PDGFRA, and BRAF mutational spectrum impacts on the natural history of imatinib-naive localized GIST: a population-based study. Am J Surg Pathol. 2015;39(7):922-30.

30. Stratakis CA, Carney JA. The triad of paragangliomas, gastric stromal tumours and pulmonary chondromas (Carney triad), and the dyad of paragangliomas and gastric stromal sarcomas (Carney-Stratakis syndrome): molecular genetics and clinical implications. J Intern Med. 2009;266(1):43-52.

31. Hostein I, Faur N, Primois C, Boury F, Denard J, Emile JF, et al. BRAF mutation status in gastrointestinal stromal tumors. Am J Clin Pathol. 2010;133(1):141-8.

32. Huss S, Pasternack H, Ihle MA, Merkelbach-Bruse S, Heitkotter B, Hartmann W, et al. Clinicopathological and molecular features of a large cohort of gastrointestinal stromal tumors (GISTs) and review of the literature: BRAF mutations in KIT/PDGFRA wild-type GISTs are rare events. Hum Pathol. 2017;62:206-14.

33. Brenca M, Rossi S, Polano M, Gasparotto D, Zanatta L, Racanelli D, et al. Transcriptome sequencing identifies ETV6-NTRK3 as a gene fusion involved in GIST. J Pathol. 2016;238(4):543-9.

34. Shi E, Chmielecki J, Tang CM, Wang K, Heinrich MC, Kang G, et al. FGFR1 and NTRK3 actionable alterations in "Wild-Type" gastrointestinal stromal tumors. J Transl Med. 2016;14(1):339.

35. Gastrointestinal Stromal Tumor Meta- Analysis G. Comparison of two doses of imatinib for the treatment of unresectable or metastatic gastrointestinal stromal tumors: a meta-analysis of 1,640 patients. J Clin Oncol. 2010;28(7):1247-53.

36. Sankhala KK. Clinical development landscape in GIST: from novel agents that target accessory pathways to revisiting non-targeted therapies. Expert Opin Investig Drugs. 2017;26(4):427-43.

37. Heinrich MC, Maki RG, Corless CL, Antonescu CR, Harlow A, Griffith D, et al. Primary and secondary kinase genotypes correlate with the biological and clinical activity of sunitinib in imatinib-resistant gastrointestinal stromal tumor. J Clin Oncol. 2008;26(33):5352-9.

38. Ben-Ami E, Barysauskas CM, von Mehren M, Heinrich MC, Corless CL, Butrynski JE, et al. Long-term follow-up results of the multicenter phase II trial of regorafenib in patients with metastatic and/or unresectable GI stromal tumor after failure of standard tyrosine kinase inhibitor therapy. Ann Oncol. 2016;27(9):1794-9.

39. Yeh CN, Chen MH, Chen YY, Yang CY, Yen CC, Tzen CY, et al. A phase II trial of regorafenib in patients with metastatic and/or a unresectable gastrointestinal stromal tumor harboring secondary mutations of exon 17. Oncotarget. 2017;8(27):44121-30. 

Results of College Written Exam in Clinical Microbiology & Infection 2017
 

EXAM NO.	RESULT
E17207	PASS
E17208	PASS
E17209	PASS
E17210	FAIL

Candidates who failed in written exam cannot proceed further in Fellowship Assessment in 2017.
Passed candidates can proceed further in Fellowship Assessment in 2017.

Volume 2, Issue 2 (click here to download the full pdf version)

Message from the President

Four years ago, I took up the challenging post of President of The Hong Kong College of Pathologists. It is time to pass the responsibility to my capable successor after the AGM this year.

The College has faced challenges while trying our best to achieve the most important mission of safeguarding the quality of training and ensuring high standard of pathology service to our community.

With the aging population and various factors, the demand on medical care in Hong Kong has been increasing. It is known that the majority of clinical decisions need the support of medical laboratory investigations. The opinions of pathologists are crucial in the prevention, diagnosis, and treatment of disease.

Indeed, The Hong Kong College of Pathologists is getting more and more represented in various task forces and specialists panels involved in health care, contributing our professional opinions.

Since the establishment of International Pathology Day in liaison with international pathology community, the College has been organizing an annual workshop for secondary school students. It is our target to let the general public know more about our profession and appreciate our contribution, and to attract potential trainees to our profession.

Thanks to the joint effort of various specialties in Pathology, we are now at the final stage of establishing a post-specialty fellowship in Genetic and Genomic Pathology. This is an important move to face the increasing application of such knowledge in dfferent facets of medicine.

Better planning of manpower and succession is important in the provision of reliable medical services. The Academy and our College hopefully can play more active roles in this aspect.

This season of examination has recently been concluded. A new generation of specialist pathologists is born. On behalf of the College, I would like to extend my sincere welcome and congratulations to all new Fellows and Members. More importantly, I also wish to applaud to all trainees who have bravely endured the serious training and examinations, irrespective of the results. We should also thank all the trainers for their dedicated supervision, and the families of our trainees and Fellows for their continuous support.

Last but not least, I would like to thank all members and friends of the College for your support to College activities. The active participation from our new Fellows is particularly welcome to ensure the success of our profession in serving the community.

Professor CHEUNG NgaYin, Annie
President, November 2017 

 

 

Volume 2, Issue 1 (click here to download the full pdf version)

Message from the President

Pathology is a medical specialty integrating personal experience and cutting-edge techniques. As a professional body committed to the upkeep and assurance of high-quality pathology practices, our College is dedicated to equipping our fellows with the ability to meet the challenges of evolving advancement in techniques and increasing expectation of the community. Concurring with the initiative by Hong Kong Academy of Medicine to promote training in genetics and genomics in several specialties, our College has been working on establishing a post-specialty fellowship in Genetic and Genomic Pathology under a special task force led by Dr Michael CHAN involving Specialty Board Chairpersons, Chief Examiners and representatives from various pathology specialties. Continued input of opinions from fellows and trainees is important.

We are encouraged by the success of the International Pathology Day Workshops targeted at high school students. The success is attributed to the hard work of a team of young fellows and trainees from various pathology specialties under the leadership of Dr Leon LAI. This year, such a workshop will be conducted again at around 15 November 2017. We shall continue to count on selfless support from fellows and trainees.

The College will continue to enhance communication with overseas and local professional bodies. There are representatives of our College in advisory groups in local administrations, and regular meetings with sister colleges overseas will continue.

The future of the profession and the College lies with our young fellows. The Academy is forming a Young Fellows Chapter for better engagement in the Academy’s activities. Each college is asked to nominate one fellow who has been conferred fellowship within the past 10 years. Dr MAK Siu Ming has been nominated to serve the first term (one year) of this Chapter.

The time of succession has also come. Nomination for Office Bearers and Councillors will be open soon. Your active participation is crucial for the success and prosperity of the pathology profession.

Professor CHEUNG Nga Yin, Annie
May 2017

Laboratory testing for Direct Oral Anticoagulants (DOACs):

Are we ready?

 

Volume 12, Issue 1 January 2017  (download full article in pdf)

 

Editorial note:

In this topical update, Dr Rock Leung reviews the testing strategy and quality assurance issues on laboratory testing for direct oral anticoagulant (DOACs). We welcome any feedback or suggestions. Please direct them to Dr Rock Leung (e-mail: leungyyr.ha.org.hk) of Education Committee, the Hong Kong College of Pathologists. Opinions expressed are those of the authors or named individuals, and are not necessarily those of the Hong Kong College of Pathologists.

 

Dr. Rock LEUNG
Associate Consultant, Division of Haematology, Department of Pathology and Clinical Biochemistry
Queen Mary Hospital, Hong Kong

 

Abbreviations

DOACs	Direct oral anticoagulants
FIIa	Thrombin
PK	Pharmacokinetics
PD	Pharmacodynamics
PT	Prothromhin time
APTT	Activated partial thromboplastin time
TT	Thrombin time
dTT	Diluted thrombin time
ECT	Ecarin clotting time
DRVVT	Diluted Russell’s viper venom time

 

Introduction

The newly available Food and Drug Administration (FDA) -approved oral anticoagulants, namely dabigatran extexilate, rivaroxaban, apixaban and edoxaban, have been more commonly used nowadays for treatment and prophylaxis of venous thromboembolism, as well as for prevention of stroke in non-valvular atrial fibrillation. This new class of anticoagulants has been referred as novel oral anticoagulants (NOACs), target-specific oral anticoagulants (TOACs), or direct oral anticoagulants (DOACs). For the sake of standardization, the International Society for Thrombosis and Haemostasis (ISTH) Scientific and Standardization Committee (SCC) for the control of anticoagulation recommends the term DOACs. DOACs have been shown to be at least as effective as warfarin in various clinical trials. Moreover, there was reduced incidence of intracranial haemorrhage reported in some studies when compared with warfarin [1]. Unlike warfarin, DOACs do not need routine therapeutic monitoring given their predictable pharmacokinetics (PK), pharmacodynamics (PD) and wide therapeutic windows. There are, however, clinical conditions that measurement of anticoagulation activity of DOACs is necessary or potentially useful, e.g. before invasive procedures, during adverse events like break-through bleeding or thrombosis, and pre- and post-administration of reversal therapy for patients with DOACs overdose. Thus, there is a role for laboratory, by testing for DOACs, to help clinicians on patient management. In addition, it is the responsibility of the laboratory to acknowledge the interferences of DOACs on conventional and special coagulation tests as part of the laboratory quality assurance in the era of gaining popularity of DOACs usage.

 

Mechanisms of actions of DOACs

In contrast with heparin that can only inhibit free protease, DOACs are rapidly-acting, target-specific anticoagulants that inhibit both the free and bound activated serine protease [2]. The fact that DOACs can inactivate bound serine protease explains their more robust action than warfarin or heparin. Dabigatran is a direct thrombin (IIa) inhibitor while rivaroxaban, apixaban and edoxaban are direct inhibitors of activated factor X (Xa). Most of the DOACs are cleared by liver and kidney, with the exception of dabigatran being almost exclusively excreted by kidney. DOACs reach peak plasma levels within approximately two hours and plasma trough levels within 12 hours or 24 hours depending on their frequency of administration [3]. The DOACs can be withhold a few days before elective surgery or invasive procedures due to their short half-lives and favourable pharmacokinetics.

 

To test or not to test?

Routine monitoring of DOACs is not required. Testing on patients on DOACs is generally indicated in certain clinical circumstances, including acute bleeding, suspected DOACs overdose, drug interaction, in patients with impaired renal function, before surgery or invasive procedure in patients who have taken the drug beyond 24 hours and with creatinine clearance of <50 mL/min or with extreme body weight [4]. Recently, more pharmacokinetics and pharmacodynamics data on indications of clinical testing came up. Currently it is recommended that checking of drug-specific peak and trough levels for DOACs should be performed for patients with body mass index (BMI) of >40 kg m^2 or weighted over 120 kg [5]. There is currently no consensus on when to test for DOACs activities when these drugs are to be used in women with childbearing potential. One should however note that animals studies have shown teratogenic effect of dabigatran, edoxaban and rivaroxaban, these drugs were assigned by the FDA as pregnancy category C, reflecting their potential teratogenicity. Whereas no teratogenicity has been demonstrated in animals for apixaban as of today, it was categorized as pregnancy catergory B by FDA [6]. On the other hand, the use of DOACs is considered an off-label clinical application for paediatric thromboemobolic diseases [7]. It is not unreasonable to obtain information about anticoagulation activity by laboratory assay for this special group of patients, as in the case of low-molecular-weight heparin (LMWH) usage in select paediatric patients.

Given the predictable pharmacokinetics of DOACs, it was proposed that a pharmacokinetic strategy by stopping the drug for a time frame adequate for washout of drug effect is safe before surgery or invasive procedures. This approach can only be applied for planned surgery or invasive procedures, with available information regarding patient’s renal function as well as the dose and timing of the last DOAC administration. For emergent or unplanned procedures in patients with renal insufficiency or unplanned procedures when the timing of the last DOAC administration is uncertain, measurement of residual drug level will be valuable to assist clinical decisions, including the assessment of bleeding risk and the need for antidote for prompt reversal of DOAC effect before surgery. In life-threatening bleeding associated with the use of DOACs, the measurement of drug level can supplement clinical information to determine whether the bleeding is contributed by the anticoagulation effect of DOACs and whether the administration of DOAC-specific antidotes is required. If antidote is applied, laboratory test can monitor the extent of reversal.

 

What tests to do?

The ideal test for DOACs shall be accurate, readily available on a 24-hour basis in order to accommodate emergency clinical situations, and with a reasonably short turnaround time (TAT).
Gold standard method using ultra-performance liquid chromatography – tandem mass spectrometry (UPLI-MS/MS) provides the most accurate information about the drug levels for patients on DOACs. However, the test is not readily available in most of the laboratories.

Routine coagulation screening tests, i.e., prothrombin time (PT), activated partial thromboplastin time (APTT) or thrombin time (TT), have been suggested as screening tests for DOACs. For routine coagulation screening tests to be useful and suitable for testing for DOACs, linearity and adequacy of test response to increasing dosage and amenability to standardization are prerequisites [8]. For dabigatran, TT is readily available in most laboratories and prolongation of clotting time is linearly and dose-dependently related to dabigatran concentrations. However, responsiveness is excessive. Therefore, a normal TT should rule out a dabigatran anticoagulant effect but the degree of prolongation poorly reflects drug concentration. Dilute TT (dTT), i.e., testing of TT on diluted plasma, is adequately responsive to dabigatran and suitable for assessment of dabigatran activity. Ecarin clotting time (ECT), using ecarin for the conversion of FII to meizothrombin, to assess anticoagulant effect of dabigatran was also shown to have satisfactory linearity and responsiveness to increasing dabigatran concentrations. APTT, though being demonstrated to have satisfactory responsiveness to dabigatran, lacks linearity upon increasing drug concentration and there is significant inter-reagent variability [9]. PT is insensitive to dabigatran and not suitable for testing.

Rivaroxaban prolongs the PT in a concentration-dependent manner, but the correlation is generally weak and became weaker with increasing drug concentration. Significant reagent-dependent differences in assay sensitivity are noted in multiple studies, limiting its use for assessment of rivaroxaban activity if the in-house thromboplastin reagent for routine coagulation screening is insensitive to rivaroxaban [10]. APTT is insensitive to rivaroxaban and shall not be used for assessment of rivaroxaban activity. For apixaban, both PT and APTT are insensitive to increasing drug concentrations and for edoxaban, PT performance is similar to that observed for rivaroxaban and APTT is insensitive [11].
Therefore, routine coagulation screening tests PT, APTT and TT cannot provide a reliable measurement of DOAC anticoagulant effect in most circumstances. One exception being a normal TT excludes significant residual effect of dabigatran in patients. Moreover, PT and APTT are either insensitive or show variably sensitivity to the on-therapy range of DOACs and limit their use in determining whether the drug concentration is in subtherapeutic or supratherapeutic ranges. Furthermore, these coagulation screening tests are potentially affected by the presence of lupus anticoagulants and conditions resulting in factor deficiency as in liver disease or dilutional coagulopathy. Thus, the sensitivity & specificity in reflecting the anticoagulant effect of DOACs is limited.

Anti-Xa assay is a chromogenic assay based on the measurement of residual FXa with synthetic substrates upon mixing of plasma with FXa. Although one study showed the feasibility of using of anti-Xa assay for LMWH to assess the presence of rivaroxaban [12], it is recommended to use drug-specific calibrator rather than adopting the anti-Xa assay for measurement of heparin activity due to the following reasons: 1) assays to measure indirect Xa inhibitors, e.g., LMWH, are measured in IU/ml and direct Xa DOACs are measured in ng/mL and there is no direct relationship between these two units of measure, 2) there is significant variability in measured drug concentration, as demonstrated by rivaroxaban, between various anti-Xa kits and 3) the therapeutic range, at least for apixaban and rivaroxaban, far exceeds the typical calibration range for UFH and LMWH (in the 5-9 IU/ml range) and 4) the assay is not specific for anti-Xa DOACs and will detect all anti-Xa anticoagulants2.

Commercially available drug-specific coagulation assays for testing of DOACs use calibrators and controls specific for the DOAC being measured [13-15], enabling the reporting of a drug concentration upon testing of patient’s plasma sample. Multiple calibrators and test plasma dilutions are employed to ensure the test sample responses are within the range of the calibration curve and also to allow for assessment of linearity and parallelism [16]. It was recommended that anti-Xa assay and diluted TT shall be employed when carrying out the drug-specific coagulation assay for anti-Xa inhibitor and anti-IIa inhibitor respectively, given their linear relationship and good correlation with drug concentration as measured by mass spectrometry [11]. Although an ecarin chromogenic assay (ECA) for direct IIa inhibitor and a DRVVT-based assay for both direct IIa and direct Xa inhibitors have been calibrated for testing of DOACs, ECA was shown to have suboptimal accuracy when compared UPLC-MS/MS and DRVVT-based assay would give false positive result in the presence of lupus anticoagulant [17,18]. Studies have shown that various drug-specific coagulation assays differ significantly in quantitation of the DOAC being measured when compared with UPLC-MS/MS in terms of precision and accuracy [17].

 

What is the meaning of drug concentration?

Drug-specific assay is by no means a direct measurement of drug concentration for DOACs. Instead it is an extrapolation of drug concentration by its anticoagulation activity measured by clot-based or chromogenic assay.
Therapeutic ranges of DOACs have not been validated by the manufacturing pharmaceutical companies. Moreover, there is no established range of concentrations associated with bleeding. In clinical use, expected trough and peak concentrations as predicated on prescribed dose and frequency are often taken as a reference during result interpretation of drug levels [17] (Table 1).

 

There is no consensus on whether trough level is superior to peak level when interpreting the findings during monitoring of DOACs. The sample for DOAC level is often collected at a random time during emergency clinical situations. A meaningful interpretation of drug level requires the knowledge of the time of last dose of DOAC, the drug dosage and patient’s renal and liver functions so that the trend of drug concentration over time can be better predicted.
With increasing use of DOAC assay, it is expected that DOAC plasma concentration shall be a standard study parameter in future clinical trials. This will allow the identification of drug concentration threshold associated with bleeding, the establishment of a therapeutic range for different kinds of DOACs and better definition of DOAC-induced bleeding complications.

 

Antidote for reversal of DOACs

Non-specific reversal agents like prothrombin complex concentrates, “bypassing agent” like factor eight inhibitor bypass activity (FIBA) and activated FVIIa were used for the correction of DOAC effect. They only had a general antagonizing action on the anticoagulation effect of DOAC without targeting the specific DOACs themselves. Three antidotes for the DOACs are now under various stages of development. Idarucizumab (Praxbind®), the antidote for dabigatran, is now licensed in the United States and recommended for licensing by the European Medicines Agency. Andexanet alfa, the antidote for the oral anti-Xa inhibitors, is undergoing phase III study. Ciraparantag (PER977), an agent reported to reverse the anticoagulant effects of all of the DOACs is at an earlier stage of development [19]. In life-threatening bleeding, administration of antidote or reversal agent before emergency operations shall not be delayed until the availability of test results. Otherwise, the decision on whether antidote is indicated can be guided by suitable laboratory assay as mentioned in the previous section. Drug-specific assay is considered the most suitable candidate given its superior sensitivity and probably better specificity than conventional coagulation assay and better accessibility and faster turnaround compared with mass spectrometry. Measurement of drug activity shall guide the antidote treatment and allow more effective use of this costly medicine. The importance is highlighted by one study on idaruxizumab for dabigatran reversal in which dTT was normal on study entry in nearly one quarter of the study population, indicating little or no circulating anticoagulant in this group of patients, whom benefit from the administration of idaruxizuman was minimal [20]. Although DOAC concentrations warranting the administration of antidote were recommended (e.g., a drug concentration over 50 ng/mL in serious bleeding and 30 ng/mL in patients requiring urgent intervention) [19], these actionable limits have not been validated in clinical studies.

 

Quality assurance issues on DOACs testing

Laboratories should develop customized algorithms on DOACs testing strategy for DOACs based on their need. The relative sensitivity of routine coagulation screening test, especially APTT and TT for dabigatran and PT for rivaroxaban, apixaban and edoxaban shall be validated by calibrated materials. Most published algorithms [21, 22] assume patient’s coagulation status is solely under the effect of DOACs and may not be applicable for patients with massive transfusion, disseminated intravascular coagulopathy (DIC) or presence of lupus anticoagulant that may have contributed to the abnormal coagulation screening results. Moreover, it is not practical to change the service PT and APTT reagents solely for DOACs detection.
The set up of clot-based or chromogenic drug-specific assay needs careful literature review on the performances of different commercially available assays. For example, one study reported overestimation of rivaroxaban levels with an anti- Xa assay utilizing exogenous antithrombin [23] and ISTH [4] recommended against its use. Nevertheless, the choice of commercially available assay may be limited by its compatibility with the automated coagulometers in service.
There are currently no standards or guidelines on the validation of drug-specific coagulation assays. Same principles on validation for clot-based or chromogenic coagulation assay shall follow, including testing for accuracy, within-run & between-run precisions and lower limit of quantification (LOQ). The testing of accuracy may be limited by accessibility to mass spectrometry. This can be resolved by testing accuracy against different lot of calibrators. Precision at low drug concentration is important to determine any significant residual DOAC effect in emergency setting. Assay kit with incorporation of low-level calibrators is favored over those with calibrators only covering the usual on-therapy concentration ranges. For the same reason, LOQ validation is important and the report shall report results as “less than” numerical LOQ value (ng/mL). Testing on plasma collected from normal subjects not taking DOACs shall be carried out to determine the intrinsic anti-Xa or anti-IIa activity from natural anticoagulant, e.g., antithrombin, which may also affect the lowest reportable limit of the assay.

As part of the quality assurance, PT, APTT, TT and fibrinogen activity shall be assessed for samples sent for quantitation of DOACs. When TT is prolonged, heparin contamination shall be excluded by carrying out protamine neutralization test. Before reporting the drug concentration, linearity of the calibrator curves shall be verified. Calibrator curve shall be acquired for every patient sample instead using stored calibrator curves as a control of lot-to-lot variation of calibrators for this relatively infrequent test. Results shall be reported in ng/mL, and there should be an accompanied comment about the appropriate range of results (peak or trough levels) based on publication. Drug level shall be interpreted in light of the time since last dose of DOAC intake as well as the dosage of DOAC taken. It is critical to have continuous surveillance of test performance over time. This can be achieved through enrollment in External Quality Assurance Programme (EQAP) (e.g., College of American Pathologist).

Drug-specific coagulation assay can be performed by automated coagulometers with pre-set dilution and analysis protocols with a low to moderate level on skill requirement and hence amenable to the organization of a laboratory-wide staff training programme to cater for the development of a routine 24-hour DOAC laboratory testing service. Interval refreshment training shall be organized to upkeep staff competence. Clinical pathologists shall be involved in communication with clinicians during emergency management of patients requiring DOAC testing to ensure efficient delivery of accurate information to facilitate patient management.

 

Impact of DOACs on special coagulation assay

It is important for laboratories that carry out special coagulation assay to acknowledge the interferences of DOACs on special coagulation assay. These include clot-based and chromogenic assay. ELISA-based and molecular assays are essentially not affected by DOACs (Table 2) [2, 17].

 

Conclusion

DOACs are more commonly used nowadays. While clinical indications for laboratory testing are more available, there is a pivotal role of laboratories to formulate a testing strategy for DOACs. Routine coagulation screening tests are not informative in most cases. Development of drug-specific assay for DOACs testing is needed. The interpretation of drug level generated by drug-specific assays needs to be facilitated by more data on the association between drug concentrations and bleeding risks expected in future studies.

 

Table 1. 5th – 95th percentile of peak and trough concentrations of DOACs obtained from pharmacokinetic and pharmacodynamics studies on patients prescribed with fixed dose and frequency of DOACs.

	Trough (ng/mL)	Peak (ng/mL)
Apixaban 2.5 mg twice daily 10 mg twice daily	20-94 30-412	36-100 122-412
Dabigatran 150 mg twice daily	31-225	64-223
Edoxaban 30 mg once daily 60 mg once daily	130-174 268-336	376-412 388-444
Rivaroxaban 10 mg once daily 20mg once daily	1-38 4-96	91-195 160-360

 

Table 2. Impact of DOACs on select special coagulation assays

Assay	Anti-FIIa DOAC	Anti-FXa DOAC
Clauss fibriongen	May be falsely decreased	No effect
One-stage APTT-based factor assays	May demonstrate false decrease in factor activity	May demonstrate false decrease in factor activity
One-stage PT-based factor assays	May demonstrate false decrease in factor activity	May demonstrate false decrease in factor activity
Chromogenic FVIII activity	No effect	May demonstrate false decrease in factor activity
Bethesda assay	False inhibitor present	False inhibitor present
AT activity: thrombin substrate	May demonstrate false increase in AT activity; may mask AT deficiency	No effect
AT activity: FXa substrate	No effect	May demonstrate false increase in AT activity; may mask AT deficiency
PC activity: clot based	May demonstrate false increase in PC activity; may mask PC deficiency	May demonstrate false increase in PC activity; may mask PC deficiency
PC activity: chromogenic	No effect	No effect
PS activity: clot-based	May demonstrate false increase in PS activity; may mask PS deficiency	May demonstrate false increase in PS activity; may mask PS deficiency
PS activity: chromogenic	No effect	No effect
PS activity: ELSA-based or LIA-based	No effect	No effect
LA testing	Possible to misclassify as LA present	Possible to misclassify as LA present
Activated PC resistance	Falsely increased ratio; possible to misclassify as FV Leiden mutation absent	Falsely increased ratio; possible to misclassify as FV Leiden mutation

AT, antithrombin; PC, protein C; PS, protein S, LA, lupus anticoagulant; LIA, latex immunoassay

 

References

1. Bauer KA. Targeted anti-anticoagulants. N Engl J of Med 2015;273:569-571.
2. Adcock DM, Gosselin R. Direct Oral Anticoagulants (DOACs) in the Laboratory: 2015 Review. Thromb Res 2015;136:7-12.
3. Schulman S. New oral anticoagulant agents – general features and outcomes in subsets of patients. Thromb Haemost 2014;111:575-582.
4. Baglin T, Hillarp A, Tripodi A, et al. Measuring oral direct inhibitors of thrombin and factor Xa: a recommendation from the Subcommittee on Control of Anticoagulation of the Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis. J Thromb Haemost 2013;11:756–760.
5. Martin K, Beyer-Westendorf J, Davidson BL, et al. Use of the direct oral anticoagulants in obese patients: guidance from the SSC of the ISTH. J Thromb Haemost 2016;14:1308-1313.
6. Desborough MJ, Pavord S, Hunt BJ. Management of direct oral anticoagulants in women of childbearing potential: guidance from the SSC of the ISTH: comment. J Thromb Haemost 2016; 27:1-2.
7. von Vajna E, Alam R, and So TY. Current Clinical Trials on the Use of Direct Oral Anticoagulants in the Pediatric Population. Cardiol Ther 2016;5:9–41.
8. Tripodi A. The laboratory and the direct oral anticoagulant. Blood 2013;121:4032-4035.
9. Stangier J, Rathgen K, Stahle H et al. The pharmacokinetics, pharmacodynamics and tolerability of dabigatran etexilate, a new oral directed thrombin inhibitor, in healthy male subject. Br J Clin Pharmacol 2007;64: 292-303.
10. Kitchen S, Gray E, Mackie I et al. BCSH committee. Measurement of non-coumarin anticoagulants and their effects on tests of Haemostasis: Guidance from the British Committee for Standards in Haematology. Br J Haematol 2014;166:830-841.
11. Samuelson BT, Cuker A, Siegal DM et al. Laboratory Assessment of the Anticoagulant Activity of Direct Oral Anticoagulants (DOACs): A Systematic Review. Chest. 2016 Sep 13. pii: S0012-3692(16)59148-X. doi: 10.1016/j.chest.2016.08.1462.
12. Yates SG, Smith S, Tharpe W et al. Can an anti-Xa assay for low molecular weight heparin be used to assess the presence of rivaroxaban? Transfus Apher Sci 2016;55: 212-215.
13. Van Ryn J, Stangier J, Haertter S et al. Dabigatran etexilate – a novel, reversible, oral direct thrombin inhibitor: interpretation of coagulation assays and reversal of anticoagulant activity. Thromb Haemost 2010;103:1116–1127.
14. Stangier J, Feuring M. Using the HEMOCLOT direct thrombin inhibitor assay to determine plasma concentration of dibigatran. Blood Coagul Fibrinolysis. 2012;23:138-143.
15. Samama MM, Contant G, Spiro TE, Perzborn E et al. Evaluation of the anti-factor Xa chromogenic assay for the measurement of rivaroxaban plasma concentrations using calibrators and controls. Thromb Haemost 2012;107:371-387.
16. Mackie I, Cooper P, Lawrie A et al. British Committee for Standards in Haematology. Guidelines on the laboratory aspects of assays used in haemostasis and thrombosis. Int J Lab Hematol 2013;35:1–13.
17. Gosselin RC, Adcock DM. The laboratory's 2015 perspective on direct oral anticoagulant testing. J Thromb Haemost 2016;14:886-893.
18. Schmitz EM, Boonen K, van den Heuvel DJ et al. Determination of dabigatran, rivaroxaban and apixaban by ultra-performance liquid chromatography - tandem mass spectrometry (UPLC-MS/MS) and coagulation assays for therapy monitoring of novel direct oral anticoagulants. J Thromb Haemost 2014;12 :1636-1646.
19. Levy JH, Ageno W, Chan NC et al. When and how to use antidotes for the reversal of direct oral anticoagulants: guidance from the SSC of the ISTH. J Thromb Haemost 2016;14:623–627.
20. Pollack CV Jr, Reilly PA, Eikeboom J et al. Idaricizumab for dabigatran reversal. N Engl J Med 2015;373:511-520.
21. Lippi G, Favaloro EJ. Recent guidelines and recommendations for laboratory assessment of the direct oral anticoagulants (DOACs): is there consensus? Clin Chem Lab Med 2015;53:185-197.
22. Favaloro EJ, Lippi G. Laboratory testing in the era of direct or non-vitamin K antagonist oral anticoagulants: a practical guide to measuring their activity and avoiding diagnostic errors. Semin Thromb Hemost 2015;41:208-227.
23. Mani H, Rohde G, Stratmann, G et al. Accurate determination of rivaroxaban levels requires different calibrator sets but not addition of antithrombin. Thromb Haemost 2012;108:191–198

 

NOTICE OF ANNUAL GENERAL MEETING

Download the AGM 2016 Notice

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NOTICE is hereby given that the 25th Annual General Meeting (AGM) of The Hong Kong College of Pathologists will be held at the Pao Yue Kong Auditorium, the Hong Kong Academy of Medicine Jockey Club Building, 99 Wong Chuk Hang Road, Aberdeen, Hong Kong on 26 November 2016 at 5:00 p.m. with the following agenda:

1. To confirm the minutes of the 24th AGM held on 28 November 2015 
2. To deal with any business arising from the minutes
3. To receive the Report of the Council on College activities (2015-2016)
4. To receive the Auditor’s Report and Financial Statements for the period from 1 July 2015 to 30 June 2016 
5. As special business, to consider and, if thought fit, to pass the following Resolution which will be proposed as a Special Resolution:-

• SPECIAL RESOLUTION
• THAT:
• the new articles of association in the form produced to the meeting and watermarked “Amended”, and initialled by the Chairman of the meeting for the purpose of identification, (“New Articles”), be and are hereby approved and adopted as the articles of association of the College in substitution for and to the exclusion of the articles of association of the College in force immediately before the passing of this Special Resolution.
• (please see Annex)

6. To re-appoint Auditor
7. To re-appoint Honorary Legal Advisor
8. To elect Office Bearers and Council Members
9. Any other business

Dated the 20th day of October 2016.

By Order of the Council

TANG Wai Lun
Registrar

Programme of the 25th Annual General Meeting

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26 November 2016, Saturday

Hong Kong Academy of Medicine Jockey Club Building, 99 Wong Chuk Hang Road, Aberdeen, Hong Kong

Download the AGM 2016 Timetable

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1:00 p.m. – 4:30 p.m.	The 12th Trainee Presentation Session
5:00 p.m. – 5:45 p.m.	The 25th Annual General Meeting
5:45 p.m. – 6:00 p.m.	Reception
6:00 p.m. – 6:50 p.m.	Conferment Ceremony Admission of New Fellows and Members and Presentation of Fellowship and Membership Certificates Conclusion of Conferment Ceremony
6:50 p.m. – 7:00 p.m.	Group Photo of Stage Party
7:00 p.m. – 8:00 p.m.	The 25th T. B. Teoh Foundation Lecture: “Digital Workflow in Anatomical Pathology – On Track to Patient Safety and Beyond” Dr. LEE Kam Cheong Consultant Pathologist Department of Pathology Princess Margaret Hospital Hong Kong
8:00 p.m. – 10:00 p.m.	Chinese Banquet Dinner

 

After the revamp of the classic website, we need to update the QAP webpage to fit the new system. Below is a brief introduction that may help users transiting to the new platform: 

1. The new webpgae is password protected, and the traditional secret code for amendment will be depreciated
2. The password is set to be identifical to your QAP participation code.
3. You are strongly advised to update the password after your first login by clicking your user icon in the left upper corner of the top menu.
4. Your QAP history will be tabulated out once you logged in.
5. You can submit your answer through the QAP answer form by clicking the link at the left upper corner of the top menu.
6. Your submission will be visible on the mainpage once you refresh the page.
7. You can amend the result by re-input the QAP case through the same QAP ansver form. The old entry will be idntified by the QAP question number (APXXX).

The deadline of submission o f the current round will be 31 October. Sorry for the delay in launching the input form. Further enhancement of the webpage is also in progress.

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