Test Details
Methodology
Flow Cytometry
Result Turnaround Time
5 - 7 days
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
Use
Diagnose myasthenia gravis (MG); monitor response to treatment of myasthenia gravis
Limitations
In rare cases AChR antibodies can be found in patients with other autoimmune disorders or with thymoma without Myasthenia Gravis (MG).
The causative autoantibody cannot be identified in up to 10% of patients with MG.
This test was developed and its performance characteristics determined by Labcorp. It has not been cleared or approved by the Food and Drug Administration.
References
Custom Additional Information
The majority of patients with MG have antibodies to the acetylcholine receptor (AChR) and, less frequently, to other proteins at the postsynaptic membrane of the neuromuscular junction. AChR antibodies impede neuromuscular transmission by a range of pathogenic mechanisms including the alteration of tissue architecture and/or by causing a reduction of the density or functionality of AChRs. Three functionally different types of antibodies against muscle AChR can be measured.
AChR modulating antibodies crosslink receptor subunits in such a way as to cause the receptors to be internalized and degraded in a process known as antigenic modulation. Modulating antibodies are implicated with an increased risk of thymoma and the majority of patients with thymoma and MG have modulating antibodies.
Specimen Requirements
Specimen
Serum
Volume
0.5 mL
Minimum Volume
0.3 mL (Note: This volume does not allow for repeat testing.)
Container
Serum from a red-top tube; serum from a gel tube
Stability Requirements
Temperature | Period |
|---|---|
Room temperature | 14 days |
Refrigerated | 14 days |
Frozen | 14 days |
Freeze/thaw cycles | Stable x3 |
Storage Instructions
Room temperature
Causes for Rejection
Improper labeling; gross microbial contamination; specimen contaminated with anticoagulants; chyous serum; plasma specimen; excessive hemolysis
LOINC® Map
| Order Code | Order Code Name | Order Loinc | Result Code | Result Code Name | UofM | Result LOINC |
|---|---|---|---|---|---|---|
| 505225 | AChR-modulating Ab | 99062-2 | 505199 | AChR-modulating Ab | % | 99062-2 |
| Order Code | 505225 | |||||
| Order Code Name | AChR-modulating Ab | |||||
| Order Loinc | 99062-2 | |||||
| Result Code | 505199 | |||||
| Result Code Name | AChR-modulating Ab | |||||
| UofM | % | |||||
| Result LOINC | 99062-2 |