CD19 + CD 38+ regulatory B lymphocytes as exploratory prognostic markers of steroid‐induced remission in treatment‐naïve adult immune thrombocytopenia

Summary Corticosteroids are commonly used as first‐line therapy for immune thrombocytopenia (ITP) to suppress immune‐mediated platelet destruction. However, some patients fail to respond, and prolonged use is associated with significant adverse effects, necessitating alternative therapeutic modalities. The aim of this study was to evaluate the role of Cluster of differentiation (CD)19 + CD38 + B cells with presumed regulatory potential as exploratory prognostic markers of steroid‐induced response in treatment‐naïve adult ITP patients. This prospective cohort study included 37 adults with newly diagnosed primary ITP treated with a standardised dexamethasone regimen at a single centre between November 2021 and June 2023. CD19 + CD38 + B cells were quantified using flow cytometry. Treatment response at 12 weeks was assessed. Multivariate logistic regression analysis was performed to determine independent prognostic markers of response. Complete response was achieved in 43% of patients, while 57% had steroid‐refractory disease. Univariate analysis identified baseline platelet count, bleeding manifestations, age and response time as significant factors. Multivariate analysis demonstrated that a higher baseline percentage of CD19 + CD38 + cells independently predicted steroid‐induced remission ( p < 0.001). Receiver operating characteristic (ROC) analysis identified a cut‐off value >2.6% for predicting remission ( p = 0.001). Baseline CD19 + CD38 + B‐cell levels may serve as a useful biomarker for predicting steroid response in ITP.