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Voltage-Gated Potassium Channel (VGKC) Antibody with Reflex to LGI1 and CASPR2 Screen and Titer, Serum

VGKC R
Example Reports
Negative
Positive

Ordering Recommendation

Screening test for voltage-gated potassium channel (VGKC) antibody receptor complex-associated autoantibodies with test reflex to CASPR2 and LGI1 antibodies. Antibodies are associated with acquired neuromyotonia, limbic encephalitis, painful neuropathy, Morvan syndrome, and rare tumors (eg, thymoma, small-cell lung cancer).

New York DOH Approval Status

This test is New York state approved.

Specimen Required

Patient Preparation
Collect

Plain red or serum separator tube.

Specimen Preparation

Separate serum from cells within 1 hour. Transfer 4 mL serum to an ARUP Standard Transport Tube. (Min: 0.5 mL)

Storage/Transport Temperature

Refrigerated.

Unacceptable Conditions

Plasma. Severely lipemic or icteric specimens.

Remarks
Stability

After separation from cells: Ambient: 72 hours; Refrigerated: 2 weeks; Frozen: 1 month (avoid repeated freeze/thaw cycles)

Methodology

Quantitative Radioimmunoassay/Semi-Quantitative Cell-Based Indirect Fluorescent Antibody

Performed

Tue

Reported

1-8 days

Reference Interval

Test Number
 Components
 Reference Interval
  Voltage-Gated Potassium Channel Ab, Ser 31 pmol/L or less

Interpretive Data

Voltage-Gated Potassium Channel (VGKC) antibodies are associated with neuromuscular weakness as found in neuromyotonia (also known as Issacs syndrome) and Morvan syndrome. VGKC antibodies are also associated with paraneoplastic neurological syndromes and limbic encephalitis; however, VGKC antibody-associated limbic encephalitis may be associated with antibodies to leucine-rich, glioma-inactivated 1 protein (LGI1) or contactin-associated protein-2 (CASPR2) instead of potassium channel antigens. A substantial number of VGKC-antibody positive cases are negative for LGI1 and CASPR 2 IgG autoantibodies, not all VGKC complex antigens are known. The clinical significance of this test can only be determined in conjunction with the patient's clinical history and related laboratory testing.

This test was developed and its performance characteristics determined by ARUP Laboratories. It has not been cleared or approved by the US Food and Drug Administration. This test was performed in a CLIA certified laboratory and is intended for clinical purposes.


Component Interpretation
Voltage-Gated Potassium Channel (VGKC) Antibody, Serum Negative
Indeterminate
Positive		 31 pmol/L or less
32-87 pmol/L
88 pmol/L or greater

Compliance Category

Laboratory Developed Test (LDT)

Note

If VGKC is Indeterminate or Positive, LGI1 Antibody IgG and CASPR2 Antibody IgG will be added. If LGI1 antibody IgG is positive, then LGI1 antibody IgG titer will be added. If CASPR2 antibody IgG is positive, then CASPR2 antibody IgG titer will be added. Additional charges apply.

Hotline History

View Hotline History

 

Hotline History

Date of Change
Test Name Change
Methodology
Performance/Reported Schedule
Specimen Requirements
Reference Interval
Interpretive Data
Note
CPT Code
Component Change
Other Interface Change
New Test
Inactive
08/21/2023
X
N/A

CPT Codes

83519; if reflexed add 86255 x2; if reflexed add 86256 per titer

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Components

Component Test Code* Component Chart Name LOINC
2004890 Voltage-Gated Potassium Channel Ab, Ser 41871-5
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.

Aliases

Voltage-Gated Potassium Channel (VGKC) Antibody with Reflex to LGI1 and CASPR2 Screen and Titer, Serum