THE SENSITIVITY AND SPECIFICITY OF ANTI-GM(1) ANTIBODY TESTING

Elevated titers of antibodies directed at ganglioside epitopes have be en associated with multifocal motor neuropathy (MMN), motor variant of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), amy otrophic lateral sclerosis (ALS), and other motor neuropathies. Anti-G M(1) antibodies were measured in 675 patients: 180 age- and sex-strati fied healthy blood bank controls, 182 normal controls who had full neu rologic assessment including electromyography, 121 patients with defin ite ALS, 19 patients with pure sensory neuropathy, and 173 consecutive patient serum samples submitted for GM(1) antibody testing. Antibodie s to three ganglioside epitopes were determined by ELISA: IgM and IgG anti-monosialo GM(1), asialo GM(1), and disialo GD(1b). Antibody titer s for normal subjects and patients with ALS were used to determine nor mal values and borderline levels below which 99% of normal and 99% of ALS patient titers were found. Clinical evaluation of the next 173 con secutive patients referred for anti-GM(1) antibody testing revealed 36 patients with motor neuropathies. Sera from 18 of these patients had titers above the 99% normal threshold and 14 had titers above the ALS and normal borderline threshold. All 14 with elevated sera titers were from patients with motor neuropathy or neuronopathy. Sixteen patients met the clinical and electrophysiologic criteria for MMN; 10 had elev ated titers. Ten patients had the motor variant of CIDP without conduc tion block and three had elevated titers. Anti-IgM asialo GM(1) antibo dies had the highest sensitivity and specificity. High-titer IgM antib odies against monosialo GM(1) occurred only in patients with various f orms of pure motor neuropathy (100% specificity). The sensitivity was 50% for this referral-based population.