According to results from the randomized Platelets for Neonatal Thrombocytopenia (PlaNeT-2) clinical trial, preterm neonates experienced heterogeneity of responses and overall decreased risk for death or bleeding after receiving transfusions for platelet counts above 25 x 109/L. These results were described in Blood.

In the PlaNeT-2 trial, prophylactic platelet transfusion at a threshold of 25 x 109/L compared with a threshold of 50 x 109/L in preterm neonates resulted in a 7% absolute risk reduction for mortality or major bleeding. However, not all neonates experienced benefit from use of a lower threshold.

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In this analysis, researchers applied a multivariate logistic regression to the data from the PlaNeT-2 trial to assess baseline risk for major bleeding or mortality for all 653 neonates enrolled in the trial. Rankings based on predicted baseline risk and categorization into 4 risk quartiles enabled assessment of the absolute risk difference between the 50 x 109/L and 25 x 109/L thresholds.

Median age at birth was 26.7 weeks. Overall, 143 neonates died or developed major bleeding. In the 25 x 109/L threshold group, 19% of neonates died or experienced major bleeding, compared with 26% of neonates in the 50 x 109/L threshold group.

This absolute risk difference of 7% indicated that for every 14 neonates treated at the lower 25 x 109/L threshold, 1 death or major bleed was prevented compared with transfusion at the 50 x 109/L threshold.

Of note, intrauterine growth restriction, sepsis, female sex, antenatal corticosteroids, and postnatal age were not associated with clinical outcomes. Lower gestational age, treatment assignment to the 50 x 109/L threshold group, and presence of a previous major bleed were all orthogonally correlated with increased risk for death or major bleeding.

Researchers categorized baseline predictive risk as very low (< 13%), low (13%-16%), intermediate (17%-24%), and high (> 24%). With an internally validated C-statistic of 0.63 (95% CI, 0.58-0.68), the model performed well in each of the quartiles of predicted baseline risk. Risk reduction in the 25 x 109/L threshold group varied from 4.9% in the very-low-risk group to 12.3% in the high-risk group.

The authors concluded that these results support use of 25 x 109/L as a platelet count threshold in all preterm neonates regardless of predicted risk from baseline characteristics.

Reference

  1. Fustolo-Gunnink S, Fijnvandraat K, van Klaveren D, et al. Preterm neonates benefit from low prophylactic platelet transfusion threshold despite varying risk of bleeding or death [published online October 24, 2019]. Blood. doi:10.1182/blood.2019000899