Low specificity of voltage-gated calcium channel antibodies in Lambert-Eaton myasthenic syndrome: a call for caution

As testing for neuronal antibodies become more readily available, the spectrum of conditions potentially associated with these autoantibodies has been widening. Voltage-gated calcium channel antibodies (VGCC-Ab) are no exception to this trend. The significance of an elevated VGCC-Ab titer beyond its original clinicopathological correlate, Lambert-Eaton myasthenic syndrome (LEMS) remains undetermined. We sought to determine the diagnostic significance of an elevated serum VGCC-Ab titer in a large single-center cohort of 100 patients. The majority of patients (58%) with elevated VGCC-Ab levels lacked an inflammatory or autoimmune etiology of their neurologic diagnosis. Only six cases (6%) of LEMS and two cases (2%) of SCLC (without LEMS) were identified. No significant differences in antibody titers were seen between the autoimmune and non-autoimmune groups. These findings support the notions that: (a) elevated VGCC-Ab titers without clinical correlation must be interpreted with caution, and (b) the clinical and electrodiagnostic criteria for LEMS should remain the mainstay in the diagnosis of LEMS.