Measurement of human skeletal muscle acetylcholine receptor antibodies using monkey receptors

Human skeletal muscle acetylcholine receptor (AChR) antibodies were assayed by a double immunoprecipitation technique using 125I-alpha-bungarotoxin as the label. Monkey AChRs were found to be superior to those from diabetic humans for analytical and practical reasons. The analytical sensitivity is 0.05 nmol alpha-bungarotoxin/L serum. The between-run and within-run precision (1 c.v.) of the assay are 13% and 3%, respectively. The normal range is 0-0.2 nmol alpha-bungarotoxin/L. There was no correlation between the antibody concentration and the clinical severity of myasthenia gravis. The clinical sensitivity and specificity of the assay for generalized myasthenia gravis are 79% and 96%, and for ocular myasthenia gravis 29% and 96%, respectively.