Clinical characteristics
The clinical characteristics of patients treated with HCQ and those without are listed in Table 1. In the HCQ group, the mean age of HCQ initiation was 12.0 years old, and the mean interval from ITP onset to HCQ initiation was 26.4 months. The mean platelet counts at the time of HCQ initiation was 85 × 109/L, higher than the level that usually required medication, which may be explained by the combination therapy initiated before HCQ such as corticosteroids and TRO-RAs. In the HCQ group, 50% of patients had positive ANA at baseline, 47.6% of patients suffered from symptoms associated with autoimmune diseases, and 64.7% of patients had other positive markers associated with autoimmune diseases except for ANA, such as antiphospholipid antibodies and low C3/C4. Treatments before HCQ included corticosteroids, IVIG, rituximab, TPO-RAs, and splenectomy, which previously failed in maintaining long-term effective. The median follow-up for patients treated with HCQ and those without were 56 and 34 months, respectively. Of note, at the last follow-up, 69.0% of patients in the HCQ group achieved CR/R, with a higher frequency than in the non-HCQ group (69.0% vs. 48.3%; odds ratio, 2.39; 95% CI, 1.15 to 4.95).