Acetylcholine Receptor Antibodies with MuSK Reflex by RIPA, Serum; test site BCN

Clinical Utility

Myasthenia gravis (MG) is an autoimmune disorder that leads to weakness and diminished control over voluntary muscles. It results from reduced signaling in the neuromuscular junction (NMJ) that connects nerves to muscle fibers. Typically, the areas of reduced functioning are the muscles of the eyes, face, and throat. There are three types of acquired MG: ocular (OMG), bulbar predominant (BMG), and generalized (GMG).
In MG, the body produces antibodies (Ab) that bind with receptors in the NMJ, blocking or destroying them, thereby preventing chemical signaling from the brain to the muscles.
The majority of cases (about 85%) of MG are caused by autoantibodies targeting the acetylcholine receptors (AChR). Approximately 6% of cases are caused by autoantibodies targeting the extracellular domain of muscle specific tyrosine-kinase (MuSK) receptors. Amongst the approximately 15% of cases of MG that are found to be AChR Ab-negative, however, MuSK Abs have been reported in patients with frequencies ranging from 0 – 64%, depending on ethnic group and geographic location.
The remaining cases are considered double-seronegative MG, as the patients sera appears negative for both AChR and MuSK antibodies. These cases can be caused by autoantibodies to a variety of other proteins, including but not limited to lipoprotein-related protein 4 (LRP4), agrin, and cortactin.

Method

Radioimmunoprecipitation Assay (RIPA)

Method Description

Acetylcholine Receptor (AChR) Antibodies: This radioimmunoprecipitation assay (RIPA) uses a double antibody precipitation technique using the Kronus antigen, a genetically engineered acetylcholine receptor to assess presence of myasthenia gravis-related autoantibodies.
BC Neuroimmunology offers two AChR antibody RIPA protocols, qualitative and quantitative. All positive qualitative assays are repeated using the quantitative assay to permit comparison of titres and results reported as nanomoles of Human Acetylcholine Receptors precipitated by 1 litre of serum (nmol/L).
MuSK testing is performed after AchR Ab testing and will not be done if the patient is AchR Ab positive.

Result Included

Acetylcholine Receptor Antibodies RIPA Screen; Acetylcholine Receptor Antibodies RIPA Quantitation; MuSK RIPA Screen

Aliases/Synonyms

AChR; AChRAB; ACRAB; anti-AchR Ab; Myasthenia gravis (MG) autoantibodies; Muscle-specific Tyrosine Kinase; Muscle Specific Tyrosine Kinase

Turnaround Time

30 days

Results

Referral Location

Canada

Last Updated

2025-03-03