ANTIBODIES TO SKELETAL-MUSCLE IN MYASTHENIA-GRAVIS .1. DIAGNOSTIC-VALUE FOR THE DETECTION OF THYMOMA

The role of anti-muscle antibodies (AMA) in the diagnosis of thymoma i n patients with myasthenia gravis (MG) is evaluated. We compared ELISA and Western blot assay for antibodies to citric acid muscle extract ( a-CAE) with an immunofluorescence assay (IF). Sera from 234 selected M G patients and 123 controls were tested. There was no essential differ ence between ELISA and IF. Western blot was superior in young onset pa tients but less useful in patients with an onset beyond the age of 40 years. Unusually high post-test probabilities were found by our patien t selection criteria which seem most realistic for clinical practice. Western blot revealed no differences in specificity of AMA in thymoma and non-thymoma patients irrespective of age at onset of disease.