Rate of change in acetylcholine receptor antibody levels predicts myasthenia gravis outcome

Kojima, Yuta
Uzawa, Akiyuki
Ozawa, Yukiko
Yasuda, Manato
Onishi, Yosuke
Akamine, Hiroyuki
Kawaguchi, Naoki
Himuro, Keiichi
Noto, Yu-ichi
Mizuno, Toshiki
Kuwabara, Satoshi

¹ Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan
² Neurology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
³ Neurology, Dowa Institute of Clinical Neuroscience, Neurology Clinic Chiba, Chiba, Japan
⁴ Neurology, Matsudo Neurology Clinic, Chiba, Japan

Dr Akiyuki Uzawa, Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan; [email protected]

Received October 30, 2020

Received in revised form February 22, 2021

Accepted February 24, 2021

Contributors YK, AU and SK contributed to the study conception, design and writing of the manuscript. YO, MY, YO, HA, NK and KH contributed to the data collection and analysis. YN and TM contributed to the interpretation of data and revision of the manuscript. All authors approved the final version.

Funding This work was supported in part by the Health and Labour Sciences Research Grant on Intractable Diseases (Neuroimmunological Diseases) from the Ministry of Health, Labour and Welfare of Japan (20FC1030).

Competing interests None declared.

Provenance and peer review Not commissioned; externally peer reviewed.

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Journal of Neurology, Neurosurgery, & Psychiatry 92(9):p 963-968, September 2021. | DOI: 10.1136/jnnp-2020-325511

ABSTRACT

Objective

To investigate the association between changes in anti-acetylcholine receptor antibody (AChR Ab) levels induced by immunosuppressive treatment and myasthenia gravis (MG) prognosis at 1-year post-treatment in patients with MG.

Methods

We included 53 consecutive AChR Ab-positive patients with MG whose AChR Ab levels were remeasured within 100 days of initiating immunosuppressive treatment (median remeasuring time post-treatment: 71 (55-84) days). The AChR Ab level reduction rate (RR-AChRAb, %/day) adjusted for the time between treatment initiation, and AChR Ab level remeasurement was calculated as follows: (pretreatment-post-treatment AChR Ab level)/pretreatment AChR Ab level/days between therapy initiation and AChR Ab level remeasurement ×100. Participants were divided into two groups based on the cut-off value of RR-AChR Ab, determined using receiver operating characteristic analyses for achieving minimal manifestation (MM) or better status at 1-year postimmunosuppressive treatment. The Myasthenia Gravis Foundation of America postintervention status and MG activity of daily living (MG-ADL) score at 1-year post-treatment were compared between the two groups.

Results

The RR-AChRAb cut-off value was 0.64%/day. The high RR-AChRAb group had a higher ratio of MM or better status (90% vs 65%, p=0.03) and lower MG-ADL score (median; 1 vs 2, p=0.04) than the low RR-AChRAb group. Kaplan-Meier analyses showed the early MM achievement in the high RR-AChRAb group (p=0.002, log-rank test).

Conclusions

High RR-AChRAb is associated with a favourable outcome at 1-year post-treatment. AChR Ab remeasurement within 100 days of therapy may be useful for predicting AChR Ab-positive MG outcomes at 1-year post-treatment.