Acetylcholine receptor (AChR) antibodies are autoantibodies that mistakenly target AChRs on skeletal muscle fibers and impede communication between nerves and skeletal muscles, inhibiting muscle contractions and resulting in muscle fatigue. AChRs are present with myasthenia gravis (MG). It is believed that this disease involves destruction by the muscle cells of AChRs bound by antibodies at the skeletal muscle motor end-plate.

This measurement is considered to be the first-order test for MG in symptomatic patients. It also helps in managing response to immunosuppressive therapy. Second- and third-order tests for modulating and blocking antibodies, respectively, are ordered to confirm the diagnosis of acquired MG; distinguish acquired disease from congenital disease; and monitor the serologic process in the course of MG.

• Negative for AChR or <0.02 nmol/L (SI units are the same) by RIA

1. Collect a 7-mL blood serum sample in a red-topped tube. Observe standard precautions.

2. Label the specimen with the patient’s name, date, and test(s) ordered and place in a biohazard bag for transport to the laboratory.

1. AChR antibodies are found in about 90% of persons with generalized MG, 70% of persons with ocular MG, and 80% of persons in remission. These findings confirm the autoimmune nature of the disease.

2. Patients who have only eye symptoms tend to have lower titers than those with generalized myasthenia symptoms.

Pretest Patient Care

1. Explain test purpose and procedure. Assess for history of immunosuppressive drug treatment. Detection of AChR binding antibody is infrequent in such cases.

2. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Positive results can be found in patients with Lambert–Eaton myasthenic syndrome or autoimmune liver disease.