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PTD - 316

Test Directory - Voltage-gated Channel Antibodies

Synonyms

Voltage-gated potassium channel, VGKC, antibodies; voltage-gated calcium channel, VGCC, antibodies, CASPR2 and LGI1 antibodies.

Clinical Indications

VGCC - investigation of patients with Lambert-Eaton myasthenic syndrome(with or without small cell lung carcinoma) Cerebellar ataxia associated with small cell lung carcinoma (SCLC) Please note: Over 80% of patients with Lambert-Eaton Syndrome have antibodies. Up to 40% of patients with the syndrome have no obvious tumour at presentation, but tumours often become apparent over the next 4 years
VGKC - investigation of patients with
peripheral nerve hyperexcitability (PNH, acquired neuromyotonia or Isaac's syndrome). VGKC antibodies can also be associated with limbic encephalitis and thymoma without PNH. VGKC antibodies are found in about 35% of all PNH patients, although this rises to 80% in those with thymoma. CASPR2 (associated with Morvan syndrome) and LGI1 (associated with limbic encephalitis) antibodies are analysed if VGKC antibodies are positive.

Request Form

Combined Pathology Blood form (Yellow/Black)

Availability

Referred test: Analysed by Immunology Department, Churchill Hospital, Oxford, if specific criteria met.

Specific Criteria

Requested by Consultant Neurologist or agreed with Consultant Biochemist. Voltage gated calcium channel antibodies: In chronic disease such as Lambert Eaton syndrome, if antibodies are not positive at onset it is worth testing again in 3-6 months. Patients do sometimes become antibody positive within the first year. Once positive, it is not usual to monitor levels.
Voltage gated potassium channel antibodies: Are often a part of acute onset diseases and it would be reasonable to re-test within a few weeks dependent on clinical features. Sometimes, patient titres rise quite steeply from a low level to positive/strong positive. It is also reasonable to re-test after treatment to see the effect on antibody level.

Turnaround Time

1 month

Specimen

Serum

Volume

1 ml

Container

Yellow top (SST) tube

Causes for Rejection

Unlabelled sample; insufficient clinical information.

Reference Range

Normal result = Negative

Interpretation

Samples are screened by toxin binding assay, positive results are expressed in picomole (pmol) of bound toxin. See clinical indications for association with disease.

Lab. Handling

Processing: Aliquot (MPA) and store at 4C in separating fridge (CB39). Referral:  VCGAB and send or BPRO and save at -20C in separating freezer (CB40).


 Version 1.0 / October 2014                                                                                                    Approved by: Consultant Biochemist