Leading Edge 2020 Issue 1

8 LEADING EDGE - 2020-1 Testing for Autoantibodies There are two laboratory methods available to test for these autoantibodies; an ELISA (both in-house and commercial methods are available) and line/dot-blot (commercial methods are available). The GanglioCombi MAG and the GanglioCombi Light ELISAs from BÜHLMANN allow for the detection of autoantibodies in serum samples from patients with suspected peripheral neuropathies. The GanglioCombi MAG ELISA allows for the detection of anti-GM1, anti-GM2, anti-GD1a, anti-GD1b, anti-GQ1b and anti-MAG, testing the reactivities to IgG and IgM as a mix and separately. The GanglioCombi Light ELISA detects anti-GM1, anti-GD1b and anti-GQ1b, again with the option of using an IgG/IgM mix or separately. Due to the glycosphingolipid nature of the antigens, it makes it difficult to extract, purify and use them to devise completely reliable testing methods; it’s accepted that most methods, both ELISA and line/dot-blot, tend to perform sub-optimally. EQA Scheme An External Quality Assessment Scheme (EQAS) on anti-ganglioside antibodies, supported by the Italian Association of Neuroimmunology, was published in 2018. The EQAS collected results from 15 participating laboratories in Italy, all using a variety of testing methods (commercial and in-house ELISAs, several different commercial line/dot-blot). The laboratories were asked to analyse five anonymised serum samples, from clinically well described patients. ■Sample 1: sensory-motor Guillain-Barré syndrome (GBS) ■Sample 2: GBS ■Sample 3: IgMκ monoclonal gammopathy-associated polyneuropathy (anti-MAG antibody negative) ■Sample 4: CANOMAD syndrome (Chronic Ataxic Neuropathy, Ophthalmoplegia, Monoclonal IgM protein, cold Agglutinins and Disialosyl antibodies) ■Sample 5: multiple mononeuropathy QA for Anti-ganglioside Antibody Testing Anti-ganglioside antibodies are used in the differential diagnosis of suspected immune-mediated neuropathies. More than 20 antiganglioside antibodies act as possible biomarkers of disease in inflammatory axonal neuropathies; currently, only a few of these antiganglioside antibodies are associated with well-defined clinical phenotypes. Good medical practice recommends testing for these associated antibodies only when inflammatory neuropathies are suspected. Table 1 depicts which anti-ganglioside antibodies are most prevalent in some autoimmune neuropathies. Table 1 : Most Prevalent Pathologies and Interpretation of Autoimmune Neuropathies Ref; BÜHLMANN