Voltage-gated Calcium Channel Antibody (VGCCA)

CPT: 86596
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Synonyms

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

Expected Turnaround Time

3 - 8 days



Related Documents


Specimen Requirements


Specimen

Serum


Volume

0.5 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

Room temperature


Stability Requirements

Temperature

Period

Room temperature

14 days

Refrigerated

14 days

Frozen

14 days

Freeze/thaw cycles

Stable x3


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)


Methodology

Radioimmunoassay (RIA)


Reference Interval

0.0–30.0 pmol/L


Additional Information

Voltage-Gated Calcium Channels (VGCCs) are transmembrane protein structures that are activated by changes in local electrical membrane potential.1 Multiple types of VGCCs have been described in both the central nervous system and peripheral tissue.1,2 Activation induces changes in protein conformation allowing the influx of calcium ions into cells. VGCCs are classified according to their pharmacological properties as P/Q-, N-, L-, T- or R-type channels.3 P-type VGCCs are associated with Purkinje neurons of the cerebellum and Q-type VGCCs with cerebellar granule neurons.1 Together, P/Q-type VGCCs are primarily involved in acetylcholine release from motor nerve terminals.2,4

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder of neuromuscular transmission with distinctive pathophysiological, clinical, electrophysiological and laboratory features.4-8 Pathologic antibodies cause a down-regulation of P/Q-type VGCCs diminishing the acetylcholine-mediated transmission of the signal from the presynaptic nerve to skeletal muscles and thus, impairing muscle contraction.4,6-10 Patients with LEMS invariably experience progressive proximal muscle weakness, often accompanied by general fatigue, autonomic symptoms and areflexia.5,6 The majority of cases occur as a paraneoplastic disorder (P-LEMS) associated with a malignant tumor that is most frequently a small cell lung cancer (SCLC).4-7,9,11 Other malignancies that have occasionally been associated with Lambert-Eaton myasthenic syndrome including non-small cell and mixed lung carcinoma, prostate cancer, thymoma and lymphoproliferative disorders.7,13 SCLC is a poorly differentiated, neuroendocrine tumor that expresses P/Q-type (as well as N- and L-type) VGCC.4,7,10-14 In P-LEMS, the initial humoral autoimmune response is generated against the VGCC of tumor cells and engenders pathologic antibodies that cross-react with VGCC of presynaptic nerve endings. 4,6,7,10,12 The onset of neurological symptoms in LEMS patients will often predate the detection of the tumor, and the survival time of the P-LEMS patients is significantly longer than that of those with SCLC without neurological dysfunction.6,7,13,15,16 Prognosis is related to the presence of cancer or autoimmune disease and the severity/distribution of muscle weakness.6 Cause of death in patients with SCLC associated LEMS is typically tumor progression, whereas LEMS that is not associated with malignancy does not reduce life expectancy.6


Footnotes

1. Catterall WA, Lenaeus MJ, Gamal El-Din TM. Structure and Pharmacology of Voltage-Gated Sodium and Calcium Channels. Annu Rev Pharmacol Toxicol. 2020 Jan 6;60:133-154.31537174
2. Dolphin AC. Voltage-gated calcium channels: their discovery, function andimportance as drug targets. Brain Neurosci Adv. 2018 Oct 2;2:2398212818794805.30320224
3. Frey J, Murray A. Autoimmune encephalitis with elevated N-type calcium channelantibodies as a multiple sclerosis mimic. Mult Scler Relat Disord. 2018 Nov;26:201-203.30268041
4. Kesner VG, Oh SJ, Dimachkie MM, Barohn RJ. Lambert-Eaton Myasthenic Syndrome. Neurol Clin. 2018 May;36(2):379-394.29655456
5. Ivanovski T, Miralles F. Lambert-Eaton Myasthenic syndrome: early diagnosis is key. Degener Neurol Neuromuscul Dis. 2019 May 13;9:27-37.31191084
6. Schoser B, Eymard B, Datt J, Mantegazza R. Lambert-Eaton myasthenic syndrome (LEMS): a rare autoimmune presynaptic disorder often associated with cancer. J Neurol. 2017 Sep;264(9):1854-1863.28608304
7. Titulaer MJ, Lang B, Verschuuren JJ. Lambert-Eaton myasthenic syndrome: from clinical characteristics to therapeutic strategies. Lancet Neurol. 2011 Dec;10(12):1098-1107.22094130
8. Martin-Moutot N, De Haro L, Seagar M. Distinct evolution of calcium channel antibody types in Lambert-Eaton myasthenic syndrome. J Neuroimmunol. 2008 Jun 15;197(1):47-53.18474401
9. Lorenzoni PJ, Scola RH, Lang B, et al. Cerebellar ataxia in non-paraneoplastic Lambert-Eaton myasthenic syndrome. J Neurol Sci. 2008 Jul 15;270(1-2):194-196.18374949
10. Lennon VA, Kryzer TJ, Griesmann GE, et al. Calcium-channel antibodies in the Lambert-Eaton syndrome and other paraneoplastic syndromes. N Engl J Med. 1995 Jun 1;332(22):1467-1474.7739683
11. Gozzard P, Woodhall M, Chapman C, et al. Paraneoplastic neurologic disorders in small cell lung carcinoma: A prospective study. Neurology. 2015 Jul 21;85(3):235-239.26109714
12. Zalewski NL, Lennon VA, Lachance DH, Klein CJ, Pittock SJ, Mckeon A. P/Q- and N-type calcium-channel antibodies: Oncological, neurological, and serological accompaniments. Muscle Nerve. 2016 Aug;54(2):220-227.26789908
13. Dean S, McCracken J, Kosmider S, Herath D. Lambert-Eaton myasthenic syndrome developing post-diagnosis of small-cell lung cancer. Intern Med J. 2018 Dec;48(12):1541-1542.30518000
14. Benatar M, Blaes F, Johnston I, et al. Presynaptic neuronal antigens expressed by a small cell lung carcinoma cell line. J Neuroimmunol. 2001 Feb 1;113(1):153-162.11137587
15. Gilhus NE. Lambert-Eaton myasthenic syndrome; pathogenesis, diagnosis, and therapy. Autoimmune Dis. 2011;2011:973808.21969911
16. Wirtz PW, Lang B, Graus F, et al. P/Q-type calcium channel antibodies, Lambert-Eaton myasthenic syndrome and survival in small cell lung cancer. J Neuroimmunol. 2005 Jul;164(1-2):161-165.15904978

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
140640 VGCC Antibody 30073-1 140686 VGCC Antibody pmol/L Pending

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