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Clustered Acetylcholine Receptor Antibodies by CBA, Serum

Test ID: ACHRCBA S

Test

Aliases/Synonyms

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

Method

Live Cell-based Assay (CBA)

Method Description

If ordered with Acetylcholine Receptor (AChR) antibodies by RIPA, Clustered AchR antibodies by CBA will not be done for patients who test positive by AchR Ab RIPA.

Report Includes

Acetylcholine Receptor Antibodies CBA Screen

Specimens

Serum
Requisition: The specimen should be submitted with this ICL-BC Neurology requisition.

Clinical Utility

Live cell-based assays (CBA) are considered the most effective detection assay for antibody detection in myasthenia gravis and show excellent specificity and superior sensitivity when compared to other assay techniques. A significant proportion of MG sufferers (about 10%) do not demonstrate presence of AChR or MuSK auto-antibodies (i.e., double seronegative patients) by the standard assay techniques. Cell-based assays have demonstrated the ability to detect AChR antibodies in 16-60% of MG patients previous assessed to be seronegative, improving detection sensitivity particularly in patients with milder disease presentation and in children.
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.

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.

Rejection Criteria

Lipemia Present

Test Version

15-Jun-2023

Performance / Interpretation

Method

Live Cell-based Assay (CBA)

Method Description

If ordered with Acetylcholine Receptor (AChR) antibodies by RIPA, Clustered AchR antibodies by CBA will not be done for patients who test positive by AchR Ab RIPA.

Turnaround Time

25 days

Results

Name Units Reference Range Conversion Factor
Acetylcholine Receptor Antibodies by CBA

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