VGKC Ab (Voltage-gated potassium channel Antibody), Serum Test
VGKC Ab (Voltage-gated potassium channel Antibody), Serum Test
Voltage-gated potassium channels are protein channels present on the surface of nerve cells consisting of Leucine-rich glioma-inactivated protein 1 (LGI1) and Contactin-associated protein 2 (CASPR2). They control the cell membrane potential and play an important role in cell growth, release of neurotransmitters and hormones, maintenance of cardiac activity, etc. Failure in the functioning of VGKC channels leads to severe genetic disorders and the development of tumors.
Certain tumors like small cell carcinoma of the lung, breast cancer, testicular cancer, etc. are associated with paraneoplastic syndromes specifically limbic encephalitis. Limbic encephalitis can cause neurological symptoms like seizures, behavior changes, short-term memory loss, and confusion. Studies have demonstrated that antibodies to Voltage-gated potassium channels (VGKC Ab) are present in patients with limbic encephalitis, with or without associated tumors.
Neurological symptoms improve by reduction of voltage-gated potassium channel antibodies (VGKC Ab). Treatment involves immunotherapy, such as plasmapheresis, intravenous immunoglobulin, corticosteroids, and other immunosuppressants.
What is a VGKC (Voltage-gated potassium channel) antibody test used for?
Voltage-gated potassium channel antibodies (VGKC Ab) i.e., antibodies to LGI1 and CASPR2 are found in patients with acquired neuromyotonia (40-50%), painful nerve hyperexcitability, Morvan’s syndrome, limbic encephalitis (paraneoplastic and idiopathic), chronic idiopathic pain, as well as patients with facial-brachial dystonic seizures.
This test measures the presence or absence of antibodies to LGI1 and CASPR2 in the serum.
Who should get tested?
Voltage-gated potassium channel antibodies (VGKC Ab) are linked to neurological conditions. It is often recommended in patients exhibiting unexplained neurological symptoms like
Seizures
Short-term memory loss
Psychiatric symptoms
Muscle twitching
Confusion
Behavior changes
Preparation for test
In most cases, no preparation is required for the test. However, the doctor may provide specific instructions depending on the patient’s medical history and any concurrent medications.
Interpretation of the test results
The test is reported as a negative or positive with a value of pmol/L. The relevance of levels below 300 pmol/L is uncertain. In autoimmune encephalitis, the level is often between 300-500 pmol/L. This test is interpreted as follows :
LGI1 test:
1. Positive result: It shows the presence of antibodies to LGI1 in the serum which is considered as a most common cause of limbic encephalitis.
2. Negative result: It shows the absence of antibodies to LGI1 in the serum which does not rule out the diagnosis. Results should be correlated with the clinical findings.
CASPR2 test:
· Positive result: It shows the presence of antibodies to CASPR2 in the serum which is considered as a most common cause of autoimmune encephalitis.
· Negative result: It shows the absence of antibodies to CASPR2 in the serum which does not rule out the diagnosis. Results should be correlated with the clinical findings.
FAQs
What is a voltage-gated potassium channel antibodies (VGKC Ab) test?
A voltage-gated potassium channel antibodies (VGKC Ab) test is a laboratory test that detects the presence of antibodies targeting voltage-gated potassium channel antibodies in blood or cerebrospinal fluid.
Why is a voltage-gated potassium channel antibodies (VGKC Ab) test performed?
This test is performed to diagnose various neurological conditions associated with voltage-gated potassium channel antibodies. Therefore, this test can guide treatment decisions.
How is a voltage-gated potassium channel antibodies (VGKC Ab) test performed?
This test involves the collection of a blood sample through venipuncture or cerebrospinal fluid through a lumbar puncture. The sample is further sent to the laboratory for analysis.
What do the results of the voltage-gated potassium channel antibodies (VGKC Ab) test indicate?
A positive result indicates the presence of voltage-gated potassium channel antibodies which support the diagnosis of associated neurological disorders. However, a negative result does not rule out these disorders and the final diagnosis should be decided in conjunction with clinical findings and other diagnostic tests.
Is this test readily available?
Voltage-gated potassium channel antibodies (VGKC Ab) test is available in many medical laboratories they may not be routinely performed in all healthcare settings. Specialist centers or neurology departments are more likely to offer these tests.
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