Effect of Acetylcholine Receptor Source on Detection and Quantification of Anti–Acetylcholine Receptor–Binding Antibody

Myasthenia gravis (MG),1 an illness characterized by sporadic muscle weakness that increases with activity, is a common autoimmune disease with an estimated population prevalence of 10 to 70 per 100 000 (1). Diagnosis of MG is primarily based on clinical findings but may be confirmed by laboratory test results demonstrating the presence of antibodies that recognize the neuromuscular nicotinic acetylcholine receptor (AChR). Use of an RIA precipitation method enables detection of anti-AChR antibodies in approximately 85% of patients with generalized MG(2). The AChR source, however, has been shown to affect the detection and quantification of antibodies present in the serum of MG patients(3). The AChR expressed by the rhabdomyosarcoma (RD) cell line TE671/RD has been used in the detection and quantification of anti-AChR antibodies, but results obtained with this method have not been identical to results obtained with assays based on alternative receptor sources(3)(4)(5). To investigate this phenomenon, we used our routine, in-house validated method(4)(5) to assay patient serum samples submitted to ARUP Laboratories, the national esoteric reference laboratory owned by …