Preterm neonates benefit from low prophylactic platelet transfusion threshold despite varying risk of bleeding or death.

The Platelets for Neonatal Thrombocytopenia (PlaNeT-2) trial, a multicentre randomised clinical trial, found an unexpected overall benefit of a prophylactic platelet transfusion threshold of 25 x 10^9/L compared to 50 x 10^9/L for major bleeding and/or mortality within 28 days of randomization in preterm neonates (7% absolute risk reduction).

To assess if there was heterogeneity of treatment effect and discern whether subpopulations of neonates were harmed with use of the lower transfusion threshold, the authors developed a multivariable logistic regression model to predict baseline risk of major bleeding and/or mortality. All 653 neonates were grouped into 4 risk quartiles based on their predicted baseline risk (very low, low, moderate and high risk) using clinical variables (IUGR, NEC, sepsis, etc.). Within each quartile absolute risk difference between the 50 x 10^9/L and 25 x 10^9/L threshold groups were assessed.

146 neonates died or developed major bleeding (19% vs. 26%). The internally validated C-statistic of the model was 0.63 (95% CI, 0.58–0.68). The 25 x 10^9/L threshold was associated with absolute risk reduction in all risk groups, varying from 4.9% in the lowest to 12.3% in the highest risk group.

These results suggest that a 25 x 10^9/L prophylactic platelet count threshold can be adopted in all preterm neonates, irrespective of predicted baseline outcome risk. Future studies are needed to improve the predictive accuracy of the baseline risk model.

– Jill M. Cholette (SABM reviewer)