Quantification of feto-maternal hemorrhage: Selection of techniques for a resource-poor setting

Background: Though RhD sensitization in RhD-negative mothers is now almost eradicated in the developed world, it continues to be a major health problem in developing nations like India. Inadequate immunoprophylaxis is the main reason. Adequate dose calculation of anti-D Ig is possible through estimation of correct feto-maternal hemorrhage (FMH) volume. In this regard, different methods have been used. Methods: We evaluated three quantitative techniques of estimating FMH: the Kleihauer-Betke test (KBT) and two flow cytometry (FC) techniques, i.e., the indirect immunofluorescence technique (IIFT) and direct immunofluorescence technique (DIFT). Stock solutions of both RhD-positive and D-negative cells were made, and 7 serial dilutions of RhD-positive cord cells in D-negative adult cells were prepared. Result: Both KBT and FC approximated the expected concentration of fetal RhD-positive cells in all mixtures tested. In both methods, an underestimation of fetal RhD-positive cells was observed when their expected concentration was ≥0.75%. Conclusion: Though FC is the most sensitive of all techniques, very few laboratories in developing nations can afford such a costly device, so it will be prudent for them to use KBT as the gold standard due to its rapidity, simplicity and affordability.