Department

Immunology

Local code : ACRAR

Preferred Sample Type

Acetylcholine receptor antibodies (ACRAR)

Suitable Specimen Types

Serum
EDTA Plasma

5 mL (150 uL minimum volume of serum/plasma)

Sample Processing in Laboratory

Usual

Sample Preparation

Centrifuge and separate. 150 uL of serum is necessary to allow duplicate analyses to be carried out if required.

Turnaround Time

14 days

Sample Stability

Stored in laboratory at 4C.

Acetylcholine receptor antibodies (ACRAR)

General Information

In Myasthenia Gravis (MG), autoantibodies against the Acetylcholine Receptor (AChR) of the motor end plates can cause a dysfunction of neuromuscular data transmission. This leads to weakness of vital muscles, which may be fatal. If diagnosed at an early stage, life-saving treatment is possible. MG is divided into different forms. These encompass acquired forms of MG, either generalised MG or MG with exclusively ocular syndromes, and genetic forms. MG can occur from early childhood to old age. Women, particularly young women of 20 to 30 years of age, and men older than 50 years of age are more likely than others to be afflicted with the disease.

Various serological tests are available for MG diagnostics. Most patients with MG are likely to have positive Acetylcholine Receptor Antibodies (ACRA), however a small subset of patients may instead have positive MuSK antibodies or LRP4 antibodies. A very small percentage of patients with MG are seronegative.

The current assay uses ELISA methodology for screening of all requests, with follow-up testing by Indirect Immunofluorescence (IIF) for confirmation of positive samples.

Patient Preparation

None

Notes

A negative AChR antibody result does not exclude myasthenia gravis (MG); about 10% patients may have no detectable AChR abs. In cases where AChR antibodies are negative and clinical presentation and suspicion of myasthenia remain high, further testing can be performed by Neurology for MuSK and/or LRP4 antibodies.

Patients with exclusively ocular myasthenia may also have negative AChR abs.

Due to the two methodologies used, discrepant results can occur between the quantitative ELISA method and qualitative IIF method. This is of uncertain significance and if clinical suspicion of MG remains high, consider referral to Neurology for further investigation.

Reference Range

<0.25 - 0.44 nmol/L = negative.

≥0.45 nmol/L = positive.

Reference range provided by Kit manufacturer.

KK

Specifications

EQA Scheme?: Yes
EQA Status: UKNEQAS for Acetylcholine Receptor Antibodies