High anti-acetylcholine receptor antibody (AChR Ab) reduction rate (RR-AChRAb) is associated with favorable outcomes after 1 year of treatment with immunosuppressive agents in patients with myasthenia gravis (MG), according to study findings published in the Journal of Neurology, Neurosurgery, and Psychiatry. The study also found that remeasurement of AChR Ab at 100 days of treatment may help predict 1-year outcomes in AChR Ab-positive patients with MG.

This retrospective study included a total of 53 consecutive AChR Ab-positive patients with MG. All patients had their AChR Ab levels remeasured within a 100-day period of starting immunosuppressive therapy (median AChR Ab remeasurement time post-treatment, 71 days).

The study investigators measured the RR-AChRAb and AChR Ab level using the following calculation: (pretreatment–post-treatment AChR Ab level)/pretreatment AChR Ab level/days between therapy initiation and AChR Ab level remeasurement × 100.


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Patients were categorized into 2 separate groups based on their ability to achieve minimal manifestation (MM) or better status at 1 year following immunosuppressive treatment. The study investigators compared the 2 groups using the Myasthenia Gravis Foundation of America postintervention status and MG activity of daily living (MG-ADL) score at 1 year.

A receiver operating characteristic curve of RR-AChRAb for the achievement of MM or better status after treatment identified 0.64%/day as the RR-AChRAb cut-off value. Patients with an RR-AChRAb value more than 0.64 were classified into the high group (n=30), while those with a value of 0.64 or lower were classified into the low RR-AChRAb group (n=23).

Patients in the high RR-AChRAb group had a significantly higher ratio of MM or better status compared with those in the low group (90% vs 65%, respectively; P =.03). Additionally, the high RR-AChRAb group had a lower median MG-ADL score (1 vs 2; P =.04) compared with the low RR-AChRAb group. In Kaplan-Meier analyses, the study investigators observed earlier achievement of MM in patients with high RR-AChRAb (P =.002).

A limitation of this study was its retrospective design, which may have introduced selection bias and confounding factors that could have affected the results.

The study investigators concluded that based on their findings, the “remeasurement of AChR Ab levels within 100 days after immunosuppressive treatment” is “recommended for choosing the treatment and predicting the outcome in AChR Ab-positive MG.”

Reference

Kojima Y, Uzawa A, Ozawa Y, et al. Rate of change in acetylcholine receptor antibody levels predicts myasthenia gravis outcome. J Neurol Neurosurg Psychiatry. Published online March 25, 2021. doi:10.1136/jnnp-2020-325511