PB0259 - Diagnostic Utility of full blood count screening in neonates born to mothers with moderate -severe thrombocytopenia

Background: Maternal thrombocytopenia during pregnancy is relatively common. However, the relationship between maternal and neonatal thrombocytopenia is poorly understood.

Aims: We aimed to determine whether a correlation exists between platelet counts of neonates born to thrombocytopenic mothers ( < 100 X 10^9/L) and maternal counts, given the non-evidence based practice of screening these neonates with an early full blood count (FBC).

Methods: We identified records from 557 thrombocytopenic mothers and the 337 associated newborn charts from 2018 to 2022.
Mothers with a maternal platelet count < 100 X 10^9/L prior to delivery during present gestation were included. Any thrombocytopenia that occurred outside of pregnancy or in the post-partum period was excluded.
Receiver operator characteristic (ROC) curves were generated using the ‘pROC’ statistical package on R and Area under the Curve (AUC) examined. Coordinates of the “best” fit model were examined using the ‘pROC’ statistical package.

Results: A total of 550 FBCs were taken in neonates of mothers with thrombocytopenia. 16 neonates with clinically significant thrombocytopenia (Platelet count < 100X10^9/L) were identified. “Number(s) needed to treat” (NNT) was 78 FBCs for infants requiring treatment and 183 FBCs to identify a clinically significant hemorrhage.
Maternal platelet count alone was not a significant predictor of neonatal thrombocytopenia (figure 1). The addition of trimester of onset of thrombocytopenia did not significantly improve predictive power. The coordinates of the best platelet count threshold for this dataset were then derived from the ROC curve and determined that a threshold of 78 x10^9/L maternal platelets offered the best sensitivity (74%) and specificity (68%) in this cohort.

Conclusion(s): Screening FBCs based on maternal platelet counts < 100X10^9/L has a poor diagnostic yield and accuracy.