Comparison of two techniques for the evaluation of fetomaternal hemorrhage in RhD-negative women: gel agglutination and haemoglobin F determination by flow cytometry

Background. In the treatment of RhD-negative women, it is clinically important to adjust the RhD immunoglobulin dose to the volume of the fetal-maternal hemorrhage (FMH). The present study compared a standard flow cytometry technique for FMH quantification to a simple alternative, the gel agglutination test. Methods. Blood samples were collected from 118 PhD negative women after delivery, and were analysed for the amount of FMH by both flow cytometry and the gel agglutination test. Events associated with increased FMH in a previous and current pregnancy, and with neonatal complications, were correlated to the results. Results. A FMH of 0.1 ml or more was detected in all 118 women in the study group by flow cytometry (mean 2.0 +/- 1.2 ml), but in only 31 women (35.6% of 87 with RhD positive infant) (mean FMH 0.76 +/- 1.48 ml) by the gel agglutination test (p <0.001). On multivariate regression analysis, only gestational age was a weak significant independent positive predictor for FMH (r(2) =0.037,p =0.047). Conclusion. The gel agglutination technique, as used in the range of 0.1-10 ml, is not sensitive enough to detect FMH.