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Acetylcholine Receptor Antibodies by RIPA, Serum

Test ID: ACHRIPA S

Test

Aliases/Synonyms

AChR; AChRAB; ACRAB; anti-AchR Ab; Myasthenia gravis (MG) autoantibodies

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).
AChR analysis by live cell-based assay (CBA) may be performed and reported as a confirmatory assay for borderline RIPA screen results.

Report Includes

Acetylcholine Receptor Antibodies RIPA Screen; Acetylcholine Receptor Antibodies RIPA Quantitation; Acetylcholine Receptor Antibodies CBA Screen (optional)

Specimens

Serum
Requisition: The specimen should be submitted with this ICL-BC Neurology requisition.
Billing Option: This test may be billed to the Medical Services Commission of BC - refer to Provincial Billing for eligibility and submission requirements.

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.

Test Location

BC Neuroimmunology Lab, Room S-157, 2211 Wesbrook Mall, Vancouver BC V6T 2B5

Test Version

15-Jun-2023

Specimen

Specimens

Serum
Requisition: The specimen should be submitted with this ICL-BC Neurology requisition.
Billing Option: This test may be billed to the Medical Services Commission of BC - refer to Provincial Billing for eligibility and submission requirements.

Collection Containers

Gold top (SST)

Sample Volume

5 mL

Minimum Volume

1 mL

Patient Preparation

Please indicate if patient is on or has recently had IVIG treatment.

Collection & Handling

Handling Information

Store and send frozen (preferred).

Stability

Refrigerated 7 days
Frozen 30 days

Additional Stability Information

If the specimen thaws, it is unsuitable for analysis.

Test Version

15-Jun-2023

Performance / Interpretation

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).
AChR analysis by live cell-based assay (CBA) may be performed and reported as a confirmatory assay for borderline RIPA screen results.

Turnaround Time

20 days

Results

Name Units Reference Range Conversion Factor
Acetylcholine Receptor Antibodies Screen by RIPA
Acetylcholine Receptor Antibodies by RIPA nmol/L
  • Absent: <0.2
  • Borderline: 0.2 - 2.0
  • Positive Low: 2 - 5
  • Positive Medium: 5 - 10
  • Positive High: >10
Acetylcholine Receptor Antibodies by CBA, Confirmatory (Optional)

Test Location

BC Neuroimmunology Lab, Room S-157, 2211 Wesbrook Mall, Vancouver BC V6T 2B5

Test Version

15-Jun-2023

Interface / Setup

HL7 Interface Codes

Order Code Result Codes Units

Test Version

15-Jun-2023