Frequency of anti-AChR epsilon subunit-specific antibodies in MG

A definite diagnosis of myasthenia gravis (MG) relies heavily on acetylcholine receptor (AChR) antibody testing. The relatively high number of antibody-negative patients therefore, causes frequent uncertainty in confirming the diagnosis. We evaluated the sensitivity and specificity of a new, commercially available AChR antibody test that uses an approximately equal mixture of AChR from TE671-epsilon (adult type) and TE671-gamma (fetal type) cells. This assay was used to re-examine 365 seronegative MG sera in which AChR antibody had not been detected by the standard assay that uses fetal type AChR. The new assay detected anti-AChR antibodies in 17 (15.5%) of 110 patients with ocular type and in 33 (12.9%) of 255 patients with generalized type MG. Anti-AChR epsilon subunit-specific antibodies were present in 13.7% of the patients in whom no AChR antibody had been detected by the standard assay, showing an increase from 79 to 82% in overall diagnostic sensitivity.