An improved diagnostic assay for Lambert-Eaton myasthenic syndrome

Abstract

A new immunoprecipitation assay has been established for detecting antibodies to voltage-gated calcium channels (VGCCs) in Lambert-Eaton myasthenic syndrome (LEMS), using 125I-ω-conotoxin MVIIC, which binds to P-type VGCCs, to label extracts of human cerebellum. Fifty six of 66 serum samples (85%) from patients with clinically and electrophysiologically definite LEMS were positive for the presence of VGCC antibodies, defined as a titre > 3 SD above the mean for the healthy controls (n = 10). All disease controls (n = 40) were negative. This sensitive immunoassay should prove valuable in the diagnosis of LEMS.