The study aimed to investigate the potential of serological factors in predicting symptom improvement in MG patients who underwent PP. 

After PP, we analyzed the relationship between symptom improvement and change in levels of immunoglobin G (IgG) and acetylcholine receptor antibody (AchR-Ab) in 21 patients with MG. 

Patients were dichotomized into favorable (n=11) and unfavorable (n=10) response groups based on a median MG composite improvement rate of approximately 50 [29, 56] %, observed 2 weeks after a PP course. The pre- and post-PP IgG reduction rates were higher in the favorable response group than in the unfavorable group (56 [51, 66] vs. 37 [32, 55] %, P=0.048). Likewise, in AChR-Ab-positive patients, IgG and AChR-Ab reduction rates were higher in the favorable response group than in the other (59 [51, 67] vs. 37 [32, 56] %, P=0.037, and 58 [45, 81] vs. 29 [2, 45] %, P=0.021, respectively). The binomial logistic regression analysis of the predictors for favorable response to PP demonstrated that IgG reduction rate in all patients (odds ratio (OR) 1.10 [95% confidence Intervals (95%CI) 1.01-1.20], P=0.030), and IgG and AChR-Ab reduction rates in the AChR-Ab-positive patients were significant prognostic variables (OR 1.12 [95%CI 1.01-1.24] P=0.036, and OR 1.05 [95%CI 1.00-1.10] P=0.043, respectively).

IgG reduction rate predicts symptom improvement in MG patients who underwent PP. Moreover, its measurement is quicker and simpler than that of AChR-Ab.