Acetylcholine Receptor Antibody
(AChR)

- Sample type:

Serum.

- Uses:

To help diagnose myasthenia gravis (MG) and to distinguish between MG and other conditions with similar symptoms.

- Precautions:

1) Serum blood is drawn from a vein located on the inside of the elbow or the back of the hand.

2) Ideal volume (mL): 2 mL.

3) Container: Red-top tube or gel-barrier tube.

4) No isotopes administered 24 hours prior to venepuncture.

5) Storage Instructions: Refrigerate for 14 day.

- Interfering Factors:

1) Recent radioactive scan. (-VE result).

2) people who are being treated with drugs such as penicillamine, with some small cell lung cancers, with autoimmune liver disease, with Guillain-Barre syndrome, and with Lambert-Eaton myasthenic syndrome (+VE results).

- Pre analytical errors:

1) Gross hemolysis; gross icterus; gross lipemia.

2) Improper storage.

- Post analytical errors:

1) Entering wrong parameter to the equipment as (wave length, temperature).

2) Error in calculation of the result.

- Corrective action:

A negative test result does not rule out MG. Up to 50% of those with ocular MG (affecting only eye-related muscles) and about 10-15% of those with generalized MG will be negative for AChR antibodies. Repeat testing of AChR antibodies in those with initially negative results may be useful as the concentration of antibodies may increase as the disease progresses, resulting in a subsequent positive AChR antibody test result.

- Reference range:

Negative: 0.00−0.24 nmol/L.

Borderline: 0.25−0.40 nmol/L.

Positive: >0.40 nmol/L.