Lab Code : ACR
Test Background The most sensitive and specific test for myasthenia gravis is the presence of ACR. Myasthenia gravis is a neuromuscular disorder characterised by weakness and fatigability of skeletal muscles. The aetiology involves a numerical decrease in the number of available acetylcholine receptors at the neuromuscular junctions due to an antibody-mediated autoimmune attack. Not all patients who have myasthenia gravis have positive ACR titres. ACR antibodies are seen in 45 % to 65 % of patients with ocular myasthenia and in approximately 90 % of patients with generalised myasthenia gravis. The degree of ‘positivity’ for the test results does not correlate with the severity of disease.
Clinical Indications Degenerative neuromuscular disease Respiratory crises Dysphagia Facial weakness
Reference Range 0-5 x 10-10 mol
Sample Required RST (rust top)
Sample Volume 5-10 mL (1 mL serum)
Turnaround Time 28 days
Notes Not currently performed in house; this test is referred to the Immunology Department at Oxford.