What is the Voltage-Gated Potassium Channel (VGKC) Antibodies test?

The VGKC antibodies test measures immune antibodies directed against proteins associated with voltage-gated potassium channels in the nervous system. These channels regulate nerve signalling and muscle activity, and abnormal immune targeting can disrupt normal neurological function.

Historically, the test detected antibodies labelled as “VGKC,” which are now understood to most commonly target associated proteins such as LGI1 and CASPR2. These antibodies are linked to specific autoimmune neurological syndromes rather than the potassium channel itself.

Clinically, this blood test is used to support the diagnosis of autoimmune encephalitis and related neurological conditions, particularly when symptoms develop subacutely and imaging or routine tests are inconclusive.

Why do I need a test for VGKC antibodies?

Autoimmune neurological disorders can mimic infections, psychiatric illness, or degenerative disease. VGKC-related antibodies are important because early diagnosis and treatment can significantly improve outcomes.

Testing is recommended when symptoms suggest immune-mediated nervous system involvement, especially if onset is rapid or fluctuating. Identifying antibodies helps guide specialist referral and immunotherapy decisions.

You may need a VGKC antibodies test if you experience:

• New-onset seizures without a clear cause
• Memory loss or confusion
• Personality or behavioural changes
• Muscle twitching or stiffness
• Peripheral nerve pain or weakness
• Sleep disturbance or autonomic symptoms
• Suspected autoimmune encephalitis

Benefits of the VGKC antibodies test

1. Supports autoimmune encephalitis diagnosis
   Helps identify immune-mediated causes of neurological symptoms.
2. Guides early specialist treatment
   Early detection can lead to timely immunotherapy.
3. Differentiates autoimmune from other causes
   Helps distinguish from infection or degenerative disease.
4. Explains unexplained seizures
   Particularly useful in adult-onset epilepsy.
5. Supports cognitive symptom investigation
   Relevant for memory and behavioural changes.
6. Non-invasive blood test
   Requires a simple blood sample.
7. Aids treatment monitoring
   Can support clinical follow-up in some cases.
8. Improves diagnostic confidence
   Adds objective evidence to complex neurological cases.

Step-by-step – How we offer this test

Option 1: Clinic-based blood test (UK-wide)

• Choose your nearest UK clinic
• Attend your appointment
• A clinician draws a blood sample
• Sample sent for specialist antibody analysis

Option 2: Home or hotel visit (+£60, UK-wide)

• A qualified phlebotomist comes to your location
• Blood sample taken at home or in your hotel
• No need to travel
• Same laboratory processing and reporting

Your results explained

Low / Negative VGKC antibody levels

Low or negative levels suggest no significant evidence of VGKC-related autoimmune activity.

UK reference range (negative):

• < 100 pmol/L

Autoimmune VGKC-related disease is unlikely based on this result alone.

Borderline VGKC antibody levels

Borderline results may be non-specific and should be interpreted alongside symptoms and other investigations.

UK reference range (borderline):

• 100 – 400 pmol/L

Further testing (e.g. LGI1 or CASPR2 antibodies) may be recommended.

High / Positive VGKC antibody levels

High levels indicate significant autoimmune antibody activity and are associated with VGKC-related neurological syndromes.

UK reference range (positive):

• > 400 pmol/L

Positive results usually prompt urgent neurology referral and further specialist evaluation.