Background: The Kleihauer-Betke test (KBT) is the most widely used assay for fetomaternal hemorrhage (FMH) detection in rhesus D negative women. In the current study, we sought to evaluate the performance of a flow cytometry (FCM) kit (FMH QuikQuant) using an anti-HbF antibody.
Methods: Eighty-three pregnant women, 58 umbilical cord blood (UCB) dilutions in adult blood, and 6 control samples were tested in parallel with FCM and KBT.
Results: Firstly, we compared for each assay, on the 58 UCB preparations, results obtained to dilutions prepared. FCM results showed an excellent correlation (r = 0.97), a high reproducibility with a coefficient of variation lower than 20% for values reaching 10 fetal RBCs. KBT values were correlated (r = 0.94) but exhibited a poor reproducibility. Then, we compared both techniques on all samples. FCM showed a good correlation with KBT (r = 0.87) but the KBT exhibited a systematic overestimation of the FMH. For 8 out of 83 pregnant women, KBT was positive. Five were concordant with FCM results (KBT+/FCM+). On the three discordant (KBT+/FCM-), 2 were finally classified as false positive of the KBT because a second control sample was negative and additionally, FCM identified an increased rate of F cells. One discordant case (KBT+/FCM-) remained unexplained. By receiver operating characteristic analysis, we found a threshold at 4.5 RBCs for FCM with a sensitivity of 89.8% and a specificity of 93.2%.
Conclusions: The FMH QuikQuant kit is a reliable and highly reproductive FCM method for FMH quantification.
Copyright © 2012 International Clinical Cytometry Society.