Platelet reference ranges for neonates, defined using data from over 47,000 patients in a multihospital healthcare system.

OBJECTIVE: Identifying a platelet count as abnormal (thrombocytopenia or thrombocytosis) can facilitate recognizing various disease states. However, the published reference ranges for platelet counts in neonates may be imprecise, as they were generated from relatively small sample sizes and compiled before modern platelet enumeration methods.

STUDY DESIGN: We derived new neonatal reference ranges for platelet counts and mean platelet volume (MPV) measurements using electronic data accumulated during a recent 6-year period from a multihospital healthcare system.

RESULT: Platelet counts were obtained between the first and the 90th day after birth, from 47,291 neonates delivered at 22 to 42 weeks gestation. The first platelet counts obtained in the first 3 days of life, increased over the range of 22 to 42 weeks gestation. In those born < or =32 weeks gestation, the lower reference range (5th percentile) was 104,200 microl(-1), but it was 123,100 microl(-1) in late-preterm and -term neonates. Advancing postnatal age had a significant effect on platelet counts; during the first 9 weeks, the counts fit a sinusoidal pattern with two peaks; one at 2 to 3 weeks and a second at 6 to 7 weeks. The upper limit of expected counts (95th percentile) during these peaks were as high as 750,000 microl(-1).

CONCLUSION: The figures herein describe reference ranges for platelet counts and MPV determinations of neonates at various gestational ages during their first 90 days. Expected values differ substantially from the 150,000 microl(-1) to 450,000 microl(-1) range previously used to define neonatal thrombocytopenia and thrombocytosis. The new definitions will render the diagnoses of neonatal thrombocytopenia and thrombocytosis less commonly than when the old definitions were used, because the new ranges are wider than 150,000 microl(-1) to 450,000 microl(-1).