Evaluation of the immature platelet fraction as a predictive marker of bone marrow regeneration after hematopoietic stem cell transplantation.

Introduction: Hematopoietic stem cell transplantation (HCST) is a widely used therapy in the management of hematological malignancies, leading to cytopenias that require transient transfusions. Platelet recovery (PR) following HSCT is assessed by monitoring platelet count (PC). Immature platelet fraction (IPF) is a research parameter offered by Sysmex® on XN series analyzers, enabling rapid diagnostic orientation in the event of thrombocytopenia. It has also been described as a predictive factor for PR after chemotherapy or HSCT, and thresholds have been proposed.

Methods: The objective of this study was to assess the predictive capability of IPF for PR in a prospective cohort of patients undergoing HSCT and to evaluate its utility in guiding platelet transfusion decision.

Results: An optimized A-IPF (absolute number of IPF) threshold of 2.5 × 10⁹/L was predictive of a PC greater than 50 × 10⁹/L at day 30 with a sensitivity of 78.9%, specificity of 78.6%, positive predictive value (PPV) of 83.3% and negative predictive value (NPV) of 73.3%. We were able to distinguish patients recovering PC before day 15 with an earlier %IPF peak, greater IPF recovery kinetics and faster neutrophil recovery.

Conclusion: A-IPF shows promise as a predictor of PR following HSCT. A multicenter study could help confirm both A-IPF and %IPF (IPF) clinical utility before it is made available to clinicians.