Immature Platelet Fraction: A Promising Biomarker in Various Clinical Entities

Reticulated platelets are immature platelets circulating in blood; they reflect the activity of megakaryopoiesis in the bone marrow. Therefore, they can be used as a non-invasive test in patients with thrombocytopenia in various clinical conditions. Reticulated or immature platelet assays are useful for the differential diagnosis of thrombocytopenia and for monitoring bone marrow recovery afterchemotherapy or stem cell transplantation and several other clinical entities. The concentration of retPLT in bone marrow is on the average 2–3 times higher than in peripheral blood, where they correlate with megakaryocyte numbers. The platelets persist in the circulation for 7–10 days, retPLT have a much shorter lifespan ( < 1 day). Therefore they can act as a marker of megakaryopoietic activity in the bone marrow which gives retPLT clinical and diagnostic utility. This review provides an overview of the clinical conditions in which reticulated platelets or immature platelets can be considered as a diagnostic tool or prognostic tool. This overview also indicates that more research is needed before reticulated or immature platelet assays can be applied in other clinical conditions than thrombocytopenia and after transplantation.