An enzyme-linked immunosorbent assay for antistriational antibodies associated with myasthenia gravis and thymoma: comparison with indirect immunofluorescence

Autoantibodies to the striations of skeletal muscle (AStrA) detected by immunofluorescence are useful in the diagnosis of a thymoma associated with myasthenia gravis (MG). With the intention of developing a better method, an enzyme-linked immunosorbent assay (ELISA) has been evaluated in 147 MG patients and 200 healthy controls. An additional 107 patients with various autoimmune diseases and autoantibodies were also tested. With a crude actomyosin preparation, the ELISA gave similar results to immunofluorescence, viz. positives in 42% of MG patients, but in all with a histologically proven thymoma. Less than 1% of the healthy controls were positive but false positives were found in patients with liver disease and anti-smooth muscle antibodies. After treatment of rheumatoid arthritis with D-penicillamine the titre of AStrA may rise. The ELISA was shown to be sensitive and reproducible, but immunofluorescence is a more practical method of distinguishing between the different categories of anti-muscle antibodies. ELISA should prove particularly useful for quantitation and sequential monitoring.