Aarau, November 09, 2018
The commission on Laboratory Diagnostics of the SSAI together with the local organiser Dr. Luca Bernasconi and his team arranged many interesting presentations for the 2018 Continuing Education Meeting on Medical Laboratory Immunology. Major topics of the day were myositis-specific antibodies, reporting of ANA patterns and cryoglobulin testing, harmonization of ANCA guidelines in Switzerland, detection and recognition of therapeutic monoclonal antibodies in immunofixation, and interesting case reports.
The meeting started with Dr. William Egner from the UK-NEQUAS, who presented an overview of the results from the International Consensus on ANA Patterns (ICAP) survey and the results from the cryoglobulin pilot scheme. The vast majority of laboratories correctly reported ANA patterns classified as “competent-level” by the ICAP, while discrepancies were observed in the evaluation of the nuclear speckled patterns, AC-4 and AC-5, which are considered by the ICAP as “expert-level” ANA patterns. However, inconsistencies were equally observed in “competent-level” as well as in “expert-levels”, suggesting that discrepancies were not dependent on the laboratory level of competency, but rather dependent on the different methods and substrates used. The UK-NEQAS survey on cryoglobulins illustrated an interesting example of monoclonal type I cryoglobulins that was evaluated by some laboratories as type II cryoglobulins. Noticeably, because of the particular pre-analytical conditions of the cryoglobulin analysis, the survey was based on the evaluation of pictures representing immunofixations of cryoglobulins.
The next speaker, Dr. Ingmar Heijnen from Basel, discussed the updated recommendations on ANCA testing. Going through all fifteen recommendations of the CLD of the SSAI by presenting the results of the last survey on ANCA testing in Switzerland, Dr. Heijnen showed that although some laboratories do not follow all recommendations, yet, the large majority of laboratories perform and report ANCA testing as recommended by the CLD. Dr. Heijnen pointed out the importance of using an additional assay, such as IIF, when high-quality antigen-specific immunoassay for PR3- and MPO-ANCA is the preferred method and results are positive. In particular, because of the low pre-test probability for ANCA-associated vasculitis in Switzerland, the use of a second assay would significantly reduce the amount of false-positive ANCA cases.
The last speaker of the morning program was Dr. Lionel Arlettaz form Sion. He presented three cases of patients with different myositis antibodies. The first patient was a particular case of anti-Mi2 antibodies associated with necrotizing myositis in which azathioprine and steroids treatments were not sufficient, while rituximab had good effects. The second patient showed the importance of including new antibodies in the line dots used to screen for myositis. Anti-TIF-1 gamma-positive dermatomyositis was diagnosed later with a most recent line dot and after further investigations, a dermatomyositis-associated tumour was found. The third patient had anti-HMGCR antibodies, which are observed under statin treatment, with necrotizing myositis but no tumour, and quickly improved after treatment with prednisone and methotrexate.
The first speaker of the afternoon session was Dr. Zoe Betteridge from Bath, UK, who presented results on the identification of myositis-specific antibodies by immunoprecipitation, which is more sensitive than immunoblot, but it is time-consuming and requires specialist centres. The presented method is based on the specific binding of patients’ antibodies trapped in a gel that is then incubated with radiolabelled cell extracts before undergoing protein fractionation and protein staining. Immunoprecipitation is currently used and has been used in the past to detect a wide repertoire of known and unknown auto-antigen targets related to myositis-associated antibodies. Dr. Betteridge, in addition, pointed out that although the majority of patients with myositis are autoantibody positive, there are still a high percentage of antibody negative patients.
The next speaker, Dr. Caroline Berckmeier from Basel, presented the performance comparison of line immunoassays to detect myositis-specific antibodies. She reviewed current literature and together with EQA results and the new ACR EULAR classification of adult and juvenile idiopathic inflammatory myopathies of 2017, she highlighted the relevance of anti-Jo-1 antibodies in the classification criteria. Although antibody detection is dependent on manufacturers’ variations and on wrong setting of the cut-off, line dots show an increasing relevance of myositis-specific antibodies and can be considered to be a convenient tool.
Dr. Nathan Cantoni and Dr. Luca Bernasconi from Aarau described the current treatment options and the laboratory issues with patients with multiple myeloma. Dr. Cantoni showed the different line therapies and their corresponding treatments as well as novel therapies consisting of new monoclonal antibodies and CAR T cells. Dr. Bernasconi demonstrated how to get rid of the interference caused by monoclonal antibody Daratumumab when performing electrophoresis and immunofixation. By using the Daratumumab specific immunofixation electrophoresis assay (DIRA), which is based on the incubation of mouse anti-Daratumumab antibodies with sera of patients under treatment with Daratumumab, it is possible to shift the migration of Daratumumab to a more anodal position, facilitating the evaluation of the immunofixation.
The meeting ended with three interesting case presentations. Dr. David Spoerl and Dr. Stéphane Buhler from Geneva presented a case of ANCA, Dr. Thomas Lung from Buchs described a particular patient with IgD monoclonal gammopathy, and Dr. Jens Schreiner from Zürich presented the relevance of anti-MOG antibodies in patients with suspected neuromyelitis optica spectrum disorder (NMOSD).
Alan Valaperti, PhD
FAMH candidate in clinical immunology
University Hospital Zurich