Acetylcholine Receptor Antibodies (AChR Abs) - Serum Test
Purpose: The AChR antibodies test measures the presence of autoantibodies against acetylcholine receptors in the blood, primarily used to diagnose myasthenia gravis (MG), an autoimmune neuromuscular disorder causing muscle weakness.
Sample Type: Serum (blood sample).
Key Points:

Indication: Ordered for symptoms like muscle fatigue, drooping eyelids, double vision, or weakness, suggestive of MG.
Procedure: A blood sample is drawn and analyzed for AChR antibodies (binding, blocking, or modulating types).
Normal Range: Typically, no detectable AChR antibodies in healthy individuals. Positive results indicate an autoimmune response, often linked to MG.
Significance:

Positive Result: Strongly supports MG diagnosis (present in ~85-90% of generalized MG cases).
Negative Result: Does not rule out MG; other tests (e.g., anti-MuSK antibodies or single-fiber EMG) may be needed.


Limitations: False negatives can occur in early MG or ocular MG. Rarely, AChR antibodies may be present in other conditions (e.g., thymoma, Lambert-Eaton syndrome).

Follow-Up: Positive results may lead to further tests, imaging (e.g., thymoma screening), or treatment planning (e.g., immunosuppressive therapy, thymectomy).