Deficiencies in anti-acetylcholine receptor antibody measurement in myasthenia gravis.

In a retrospective case note study of 86 patients with myasthenia gravis, 60 had an anti-acetylcholine receptor antibody assay performed by the regional immunology laboratory. Antibody was detected in 38% which compares with 66-93% in other series. Whilst the use of staphylococcal protein A to precipitate the antibody-receptor complex, rather than anti-human immunoglobulin, may be partly responsible for this low sensitivity, other methodological problems are likely to exist. It is suggested that this potentially critical assay becomes a subject for regular audit.