Lambert-Eaton Myasthenic Syndrome and Voltage-gated Calcium Channel Antibodies

Lambert-Eaton Myasthenic Syndrome (LEMS) is an autoimmune, neuromuscular transmission disorder characterized by muscle weakness and fatigue. In LEMS, voltage-gated calcium channels (VGCC) located at nerve terminals are targeted by pathogenic autoantibodies, thereby preventing calcium influx.  This results in reduced acetylcholine release into the neuromuscular junction (NMJ), yielding weaker muscle contractions.  Approximately 50-60% of LEMS cases are associated with underlying tumors (paraneoplastic), most commonly small cell lung cancer (SCLC).

Measuring VGCC antibodies is clinically useful in differentiating between neuromuscular disease and a polyneuritis. VGCC antibody positivity should be followed by tumor investigation.  If present, cancer treatment may improve symptoms of LEMS.

Anti-Voltage-Gated Calcium Channel Ab Testing at BC Neuroimmunology

The lab uses a radioimmunoprecipitation assay (RIPA) to semi-quantitatively measure VGCC antibodies in human serum.

In order to bill VGCC Ab testing to provincial health services, the assay must be ordered by a neurologist, as per MSC guidelines.

This test is performed monthly, or more frequently if the number of samples we receive warrants it.

Laboratory Requisition

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*Download the requisition onto a computer and open with Adobe Acrobat/Reader for a writeable PDF