Christine Bundell^1
1PathWest Laboratory Medicine

Autoantibodies were first associated with inclusion body myositis (IBM) in 2011 following the identification of B cells and plasma cells in IBM muscle biopsies.  Cytosolic 5”-nucleotidase 1A (C5N1A) was subsequently identified as a target antigen.

Since the antibody was first identified, testing by ELISA and immunoblot has become available. Seventeen participants are enrolled in in the RCPA Quality Assurance Myositis and Scleroderma Antibody program which includes C5N1A antibody testing.

PathWest Laboratory Medicine (PWLM) performs an in house IVD ELISA using details reported by Greenburg in 2014.  PWLM receives samples from WA, interstate and from New Zealand. 883 samples, from 841 patients have been tested for C5NIA antibodies over the last 38 months 19% of patients were C5N1A antibody positive.  Among 13 patients from Western Australia with positive C5N1A antibody results, 62% had an established diagnosis of IBM. Where clinical suspicion of IBM is high and C5N1A antibodies are positive, invasive muscle biopsy may be not be required.