Pretreatment Absolute Immature Platelet Count is a Promising Predictor of Response to Short-Term Dexamethasone Monotherapy or Combination Therapy in Newly Diagnosed Adult Primary Immune Thrombocytopenia.

Reliable indicators that can predict drug responsiveness in primary immune thrombocytopenia (ITP) patients are urgent. We aimed to establish a reference interval of percentage of immature platelet fraction (IPF%) and absolute immature platelet count (A-IPC), and assess their efficacy in discriminating ITP patients from controls, especially their predictive value for responsiveness to drug treatment. We retrospectively studied 72 treatment-naive adult patients with ITP who received Dexamethasone monotherapy or combination therapy. Baseline (pretreatment) information was collected from medical records. Reference intervals for A-IPC and IPF% were established based on controls and their effectiveness in discriminating ITP patients from controls was assessed. Predictive value of pretreatment IPF% and A-IPC at four co-primary endpoints of treatment response in patients were investigated. The 95% reference intervals for A-IPC and IPF% were (2.7-15.6) × 10/L and 1.2%-7.3%, respectively. Both A-IPC and IPF% had excellent discrimination ability for ITP patients from controls. It showed highly statistically significant differences in pretreatment A-IPC for predicting treatment response at day 7 between responders and non-responders, but not at days 14, 21 and 28. Pretreatment A-IPC had the higher area under the ROC curve with a cut-off of 0.86 than that of IPF% with a cut-off of 14.5% in predicting the treatment response in ITP patients at day 7. Pretreatment A-IPC exhibited acceptable predictive power and could be a promising predictor of response to short-term Dexamethasone monotherapy or combination therapy at day 7 in ITP patients.