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Voltage-gated Calcium Channel Antibody (VGCCA)

CPT: 83516
Updated on 09/22/2020
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Synonyms

  • Lambert-Eaton Myasthenic Syndrome Antibody
  • LEMS Autoantibody
  • VGCC Antibody
  • VGCCA

Expected Turnaround Time

6 - 8 days



Related Documents


Specimen Requirements


Specimen

Serum


Volume

0.8 mL

0.1 mL

0.8 mL


Minimum Volume

0.4 mL (Note: This volume does not allow for repeat testing.)


Container

Red-top tube or gel-barrier tube


Collection

Serum should be separated from cells within one hour and transferred to a plastic transport tube.


Storage Instructions

Refrigerate


Patient Preparation

Patient should have no radioactive isotopes administered 24 hours prior to venipuncture.


Causes for Rejection

Nonserum specimen; gross hemolysis; gross lipemia


Test Details


Use

Measurement of P/Q-type voltage-gated calcium channel (VGCC) antibodies as an aid in the diagnosis of Lambert-Eaton myasthenic syndrome (LEMS)


Limitations

Results for this test are for research purposes only by the assay's manufacturer. The performance characteristics of this product have not been established. Results should not be used as a diagnostic procedure without confirmation of the diagnosis by another medically established diagnostic product or procedure.

This procedure may be considered by Medicare and other carriers as investigational and, therefore, may not be payable as a covered benefit for patients.


Methodology

Radioimmunoassay (RIA)


Reference Interval

Negative


Additional Information

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder of neuromuscular transmission that affects the presynaptic release of acetylcholine.1-3 The release of acetylcholine from storage vesicles in the nerve ending is regulated by the influx of calcium through voltage-gated channels (VGCC). The impairment of acetylcholine release results in fatiguability and muscle weakness that is characteristic of the disease. Several subtypes of calcium channels have been described (T, L, N, P) based on biophysical and pharmacological properties. Of these, P subtypes are thought to be the most significant in LEMS.

LEMS is a paraneoplastic syndrome that is highly associated with small-cell lung carcinoma (SCLC). This association is thought to be due to antigenic similarity between proteins found in the tumor cells and the voltage-gated calcium channel proteins. Classic symptoms of LEMS include proximal muscle weakness, fatiguability, dry mouth, and impotence. When presentation is further complicated with oculobulbar weakness, these symptoms can be easily misinterpreted as myasthenia gravis (MG); however, because VGCC antibodies are positive in only ∼5% of MG patients, in comparison to ∼95% of LEMS patients, the measurement of these antibodies is very useful in distinguishing LEMS from MG.


Footnotes

1. Lennon VA. Serologic profile of myasthenia gravis and distinction from the Lambert-Eaton myasthenic syndrome. Neurology. 1997 Apr; 48(Suppl 5):23S-27S.
2. Lennon VA, Lambert EH. Autoantibodies bind solubilized calcium channel-omega-conotoxin complexes from small cell lung carcinoma: A diagnostic aid for Lambert-Eaton myasthenic syndrome. Mayo Clin Proc. 1989 Dec; 64(12):1498-1504. 2557495
3. Voltz R, Carpentier AF, Rosenfeld MR, Posner JB, Dalmau J. P/Q-type voltage-gated calcium channel antibodies in paraneoplastic disorders of the central nervous system. Muscle Nerve. 1999 Jan; 22(1):119-122. 9883867

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
140640 VGCC Antibody 30073-1 140679 VGCC Antibody 30073-1

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