Quantification of fetomaternal hemorrhage: a comparative study of the manual and automated microscopic Kleihauer-Betke tests and flow cytometry in clinical samples

Objective The purpose of this study was to evaluate the quantification of fetomaternal hemorrhage by the manual and automated microscopic analysis of Kleihauer-Betke stained slides and by flow cytometry. Study design Blood smears were stained and evaluated manually according to the Kleihauer-Betke test. The same slides were used for automated microscopy. In addition, blood flow cytometry was performed by anti–hemaglobin F immunostaining. Results Fetomaternal hemorrhage >0.1% was detected in 4 patients by manual and automated Kleihauer-Betke test and by blood flow cytometry. Fetomaternal hemorrhage was absent according to all 3 methods in 13 patients; fetomaternal hemorrhage<0.1% was detected in 27 patients by either manual or automated Kleihauer-Betke test or both. Moderate agreement was observed between the manual and automated Kleihauer-Betke test (weighted κ, 0.56; 95% CI, 0.33–0.78). Agreement between the manual Kleihauer-Betke test and blood flow cytometry was fair (weighted κ, 0.40; 95% CI, 0.15–0.66). Conclusion Automated microscopic detection of fetal blood cells in clinical samples provides accurate quantification that is comparable to the manual Kleihauer-Betke test in both small and large fetomaternal hemorrhage. Blood flow cytometry is capable only of quantifying fetomaternal hemorrhage of >0.1%.