VGKC Antibody, Serum Test

For differential diagnosis of Paraneoplastic Neurological Syndrome, Autoimmune Encephalitis, Neuromyotonia.

This test is performed for patients suspected of suffering from nervous system disorders which are of autoimmune origin.

Voltage-Gated Potassium Channel (VGKC) antibodies (predominately Anti-LGI1 and Anti-CASPR2) are associated with paraneoplastic neurological syndromes and limbic encephalitis. These antibodies may also be found in other conditions such as acquired neurmyotonia, painful neuropathy, Morvan's syndrome, and rare tumors (eg, thymoma, small-cell lung cancer). This indirect fluorescent antibody assay utilizes LGI1 and CASPR2 transfected cell lines for the detection and semi-quantification of autoantibodies.

This test helps in diagnosis of autoimmune encephalitis. It is also useful in managing patients on immunotherapy and/or plasmapheresis. The test is done to diagnose peripheral nervous sysytem disease and central nervous system diseaseas  in certain types of tumours.  

The test measures the antibodies to VGKC [antibodies to LGI1 and CASPR2] in the serum.  

This test requires a blood sample. A tourniquet (elastic) band is placed tightly on the upper arm. The patient is then asked to make a fist. This helps in the build-up of blood filling the veins. The skin is disinfected before needle insertion and the blood sample is collected in vacutainer. 

From IT masters

LGI1 test: Positive result shows presence of antibodies to LGI1 which is probably considered as most common cause of limbic encephalitis. 
Negative result indicates absence of these antibodies in the serum. Results should be correlated with the clinical findings. 
CASPR2 test: Positive result shows presence of antibodies to CASPR2 which is suggestive of auto-immune encephalitis. 
Negative result indicates absence of these antibodies in the serum. Results should be correlated with the clinical findings.