Quantification of foetomaternal haemorrhage. An analysis of two cytometric techniques and a semiquantitative gel agglutination test
Traditional tests to screen for foetomaternal haemorrhage are time-consuming and difficult to perform. The Kleihauer test is widely used but difficult to standardize. We evaluated three techniques for quantifying foetomaternal haemorrhage: a semiquantitative gel agglutination test and two flow cytometric techniques. The gel agglutination test is based on the consumption of anti-D reagent by D+ cells, analysing the reaction of the supernatant against indicator cells in a Coombs-gel card. In the two colour direct immunofluorescent technique, the sample is incubated with Per-CP labelled anti CD45 antibody, fixed with glutaraldehyde and permeabilized by exposure to Triton X-100. An aliquot is stained with an antibody to foetal haemoglobin, conjugated with fluorescein isothiocyanate or phycoerythrin. The indirect immunofluorescent technique is based on the labelling of Rh (D) antigen with an anti D reagent, followed by the addition of an anti IgG antibody conjugated with phycoerythrin. Foetomaternal haemorrhage was not detected in 75 of the 85 samples analysed by the direct immunofluorescent technique. In the remaining 10 samples, the volume was very low. Thirty-five samples with Rh (D) antigen incompatibility were analysed in parallel by the indirect immunofluorescent technique and in 15 of the 35 samples, the gel agglutination technique was also carried out. The three techniques gave similar results. The gel agglutination test can be used to screen for foetomaternal haemorrhage, while greater volumes should be quantified by flow cytometric techniques.
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