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Test Code CCPQ P/Q-Type Calcium Channel Antibody, Serum


Ordering Guidance


The profile test should not be requested in patients who have recently received radioisotopes, therapeutically or diagnostically, because of potential assay interference. The specific waiting period before specimen collection will depend on the isotope administered, the dose given, and the clearance rate in the individual patient. Specimens will be screened for radioactivity prior to analysis. Radioactive samples received in the laboratory will be held 1 week and assayed if sufficiently decayed or canceled if radioactivity remains.



Specimen Required


Only orderable as part of a profile. For more information see:

PAVAL / Paraneoplastic, Autoantibody Evaluation, Serum

MGLE / Myasthenia Gravis/Lambert-Eaton Myasthenic Syndrome Evaluation, Serum

MDS2 / Movement Disorder, Autoimmune Evaluation, Serum

PNEFS / Neuroimmunology Antibody Follow-Up, Serum


Useful For

Confirming a diagnosis of Lambert-Eaton syndrome

 

Implicating autoimmunity as a disease-causing mechanism in patients with complex neurologic presentations, particularly in those with a history of cancer

 

Implicating autoimmunity as the basis of limbic encephalitis, cerebellar ataxia, myelopathy, peripheral neuropathy, or autonomic neuropathy

 

This test is not useful as a general screening test for cancer.

Method Name

Only orderable as part of a profile. For more information see:

PAVAL / Paraneoplastic, Autoantibody Evaluation, Serum

MGLE / Myasthenia Gravis/Lambert-Eaton Myasthenic Syndrome Evaluation, Serum

MDS2 / Movement Disorder, Autoimmune Evaluation, Serum

PNEFS / Neuroimmunology Antibody Follow-Up, Serum

 

Radioimmunoassay (RIA)

Reporting Name

P/Q-Type Calcium Channel Ab

Specimen Type

Serum

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 28 days
  Frozen  28 days
  Ambient  72 hours

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

Clinical Information

This test is not offered as a standalone test but is included in the following test procedures as an aid for diagnosis of neurological autoimmunity, usually in a paraneoplastic context.

-MGLE / Myasthenia Gravis/Lambert-Eaton Myasthenic Syndrome Evaluation, Serum

-MDS2 / Movement Disorder, Autoimmune Evaluation, Serum

 

P/Q-type calcium channels regulate neurotransmitter release at motor nerve terminals and are involved in central neurotransmission.

 

A snail venom toxin, omega conopeptide MVIIC, is a specific high-affinity antagonist for P/Q-type channels.

 

Autoantibodies directed against extracellular epitopes of P/Q-type calcium channels are implicated as the effectors of the Lambert-Eaton myasthenic syndrome (LES).

 

These antibodies generally reflect an immune response against cancer.

 

P/Q-type calcium channel binding antibodies are found in 95% of nonimmunosuppressed patients with LES (100% of those with cancer) and in 20% of patients who have encephalomyeloneuropathies related to carcinoma of lung, breast, or ovary.

Reference Values

Only orderable as part of a profile. For more information see:

PAVAL / Paraneoplastic, Autoantibody Evaluation, Serum

MGLE / Myasthenia Gravis/Lambert-Eaton Myasthenic Syndrome Evaluation, Serum

MDS2 / Movement Disorder, Autoimmune Evaluation, Serum

PNEFS / Neuroimmunology Antibody Follow-Up, Serum

 

≤0.02 nmol/L

Interpretation

Values greater than 0.02 nmol/L are consistent with neurologic autoimmunity and suggest a paraneoplastic basis.

 

Values in nonimmunosuppressed patients with Lambert-Eaton syndrome are usually greater than 0.1 nmol/L.

Cautions

High-dose intravenous IgG therapy may cause false-lowering of (or negative) values.

 

Plasma specimens can yield false-positive results.

 

The influence of myeloma M proteins is uncertain.

Day(s) Performed

Monday through Sunday

Report Available

3 to 7 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

86596

LOINC Code Information

Test ID Test Order Name Order LOINC Value
CCPQ P/Q-Type Calcium Channel Ab 94349-8

 

Result ID Test Result Name Result LOINC Value
81185 P/Q-Type Calcium Channel Ab 94349-8