Significance of immature platelet fraction and CD41-positive cells at birth in early onset neonatal thrombocytopenia

Early thrombocytopenia is a common hematological abnormality in sick neonates. Here, we examined the relationship between early thrombocytopenia in neonates and parameters associated with thrombopoiesis to identify predictive factors at birth. Two hundred and forty-four neonates admitted to the neonatal intensive care unit were divided into thrombocytopenic (n = 55, 23%) and non-thrombocytopenic (n = 189, 77%) groups based on platelet counts, which were monitored within 72 h of birth. Immature platelet fraction (IPF) and platelet count at birth were determined simultaneously soon after phlebotomy with an automated hematology analyzer. Megakaryocytes and their precursors positive for CD41 in peripheral blood were examined at birth by flow cytometry. The thrombocytopenic group showed significantly higher IPF percentage and lower percentage of CD41⁺ mononuclear cells (MNCs) than did the non-thrombocytopenic group (P < 0.01). Moreover, the percentage of CD41⁺ MNCs significantly differentiated neonates with platelet counts >150 × 10³/μL at birth and nadir platelet count <150 × 10³/μL over the clinical course from neonates without thrombocytopenia. These observations suggest that the percentage of CD41⁺ MNCs at birth and IPF percentage are useful predictors of early thrombocytopenia in the majority of sick neonates.