Kleihauer-betke (KB) testing in triage to predict pregnancy outcomes associated with fetomaternal hemorrhage: a retrospective cohort study

Abstract

Objectives Fetomaternal hemorrhage (FMH) is a rare but serious obstetrical complication that can lead to severe fetal anemia causing stillbirth or renal or brain injury in survivors. The Kleihauer-Betke (KB) test estimates the amount of fetal red blood cells in Rhesus-D (RhD) negative women and is commonly performed in pregnant women following blunt injury to the uterus. The objective of this study was to determine the diagnostic and screening utility of KB testing as a triage tool in predicting adverse fetal outcomes associated with FMH. Methods A single center retrospective cohort study evaluated the diagnostic and screening performance of KB tests (n=663) in women with singleton pregnancies over a 2-year period at a large perinatal referral center. Clinical characteristics, additional investigations and pregnancy outcomes were evaluated. The primary composite outcome of adverse fetal complications associated with FMH comprised: preterm delivery, fetal growth restriction, fetal or neonatal death, fetal anemia, fetal asphyxia (5-minute APGAR score Results 641 women (97%) had KB negative and 22 (3%) had KB positive tests. The primary composite outcome between KB negative and KB positive pregnancies was similar (30% vs. 36%, p=0.54). While screening exhibited high specificity (97%), test sensitivity was poor (4%) with moderate positive and negative predictive values (36.4% and 69.7%). Conclusions KB testing is an expensive labor-intensive test that offers no diagnostic precision in the emergency triage evaluation of women with suspected FMH and should not be used on a routine basis.