The effect of HCQ on platelet counts
To analyze the effect of HCQ on platelet counts in chronic ITP children in the context of combined therapy, we conducted mixed-effect models (Table 3). Results showed that HCQ was associated with increased platelet counts, which was supported by the significant main effect of HCQ from the mixed-effects model with adjustment for confounding factors (mean difference of platelet counts between HCQ and non-HCQ groups: 23.82×109/L; 95% CI: 7.44 ~ 40.21). Besides, the insignificant interaction term from the mixed-effects model did not support the existence of correlation between the baseline ANA positivity and HCQ treatment effectiveness. The sensitivity analysis yielded similar estimates (Table S1).