If a first time AChRAb result is negative the specimen will be tested for MuSK antibodies as a reflex assay.
Specimen Collection 3.5 mL SST Serum (Preferred) 3.5 mL Plain Serum Reference Intervals
Uncertainty of measurement: 20%
Indicative - Units: nmol/L
Age Range Either Sex All < 0.44
Negative Positive Turnaround Time: Within 4 weeks, 2 days
Analysed once a month.
Current Methodology in use at LabPLUS for Neuronal antibodies
Test / Group Methodology Manufacturer
NMDAR Ab IFA (Transfected cells) Euroimmun (Germany)
panel IFA (Transfected cells) Euroimmun (Germany)
Aquaporin-4 Ab IFA (Transfected cells) Euroimmun (Germany)
Onconeuronal Line Immunoassay (LIA) NOVA, USA (IFA) and LIA
antibody panel and IFA (Monkey cerebellum) Euroimmun (Germany)
AChRAb ELISA RSR, UK
MuSK Ab RIA RSR, UK
Diagnostic Use and Interpretation
Acetylcholine receptor binding antibodies are present in approximately 90% of patients with generalised myasthenia gravis, 60% of ocular myasthenia and 60% of patients in remission. This antibody is highly specific for myasthenia gravis. Approximately 1% of patients with rheumatoid arthritis being treated with D-penicillamine develop AChR antibodies and these antibodies are seen occasionally in patients after bone marrow grafts. Assays for antibody levels may be useful in monitoring the course of individual patients.
Myasthenia gravis (MG) is a condition in which severe weakness of critical muscles (respiratory) can be fatal. Autoantibodies against the acetylcholine receptor (ACHRAB) are responsible for failure of the neuromuscular junction in MG.
The prevalence of MG is estimated to be between 40-50 cases per million people. MG can occur from early childhood to old age. Women, particularly young women of 20-30 years of age, and men older than 50 years of age are more likely than others to be afflicted with the disease.
Measurement of ACHRAB is a highly specific method for the diagnosis of MG as well as for monitoring the progression of the disease. Up to 90% of patients with acquired MG have detectable levels of circulating ACHRAB. However, the absence of ACHRAB does not exclude a diagnosis of MG. An electromyographic test may be useful. Consultation with a neurologist is advised.
In contrast to patients with generalized myasthenia gravis, only 60% of MG patients with purely occular symptoms exhibit ACHRAB. ACHRAB are not present with genetic forms of MG (approximately 5-10% of all cases). However, ACHRAB have been found in some first-degree relatives of patients with MG. The presence of ACHRAB without clinical manifestations of MG is rare and is usually associated with other disorders with an increased risk for MG.
1. Euroimmun ACHO kit insert.
For further information contact Dr Richard Steele