Test Update: Myasthenia Gravis

Mayo Clinic recently completed a four-year review of Myasthenia Gravis serum evaluations and will be implementing changes to our testing algorithm.

Why the changes:

• Increase diagnostic specificity while maintaining high sensitivity – 90% sensitive, 95% specific

• Simplify ordering

• Improve turn-around-time

Research findings are published in Neurology and available online by clicking on this title: “Improving accuracy of myasthenia gravis autoantibody testing by reflex algorithm”

• Accuracy of MG serological testing is improved by reflexing acetylcholine-receptor-binding (AChR-Bi) positive cases to acetylcholine-receptor-modulating (AChR-Mo)

• Striational (STR) and other reflexed cancer evaluation autoantibodies (GAD65, Alpha-3, CRMP5 and VGKC) did not provide value beyond CT-chest imaging

• MG patients negative for AChR-Bi and AChR-Mo most often have muscle-specific receptor tyrosine kinase (MuSK) autoantibodies present

Difference from old method will involve:

• Initial testing for AChR-Bi only (eliminates up-front testing for AChR-Mo and STR)

• Automatic reflex to MUSK when AChR-Bi is negative to improve turn-around time

• Automatic reflex to AChR-Mo when AChR-Bi is positive to reduce false positives

• The AChR-Mo assay method will change from a quantitative bioassay to qualitative FACS live CBA

• Eliminate reflex to “paraneoplastic” antibodies (GAD65, Alpha-3, CRMP5 and VGKC)

In short, if the AChR-binding is positive, AChR-modulating will be performed. If AChR-binding is negative, MuSK will be performed.

This change will go into effect on May 11, 2021. Please direct questions and inquiries to the Referral/Sendout Department via the “contact us” link above.

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