ANTENATAL PLATELET ANTIBODY TESTING BY FLOW-CYTOMETRY - RESULTS OF A PILOT-STUDY

Background: Maternal platelet antibodies can cause fetomaternal alloim mune thrombocytopenia (FMAT), which has significant mortality and morb idity even in a first pregnancy. Prenatal diagnosis of FMAT has not pr eviously been possible in the first affected pregnancy. Study Design a nd Methods: Using flow cytometry, a sensitive, inexpensive test for th e detection of platelet antibodies has been developed. It was adapted for use as a possible antenatal screening test, and 600 pregnant women were tested in a pilot study. Results: In the study group, two women tested positive for platelet-specific IgG antibodies, one for anti-HPA -1a and the other for anti-HPA-1a with anti-HLA. In each case, the fet us was found to be affected in utero, and treatment was initiated befo re successful delivery. Another woman was shown to have a platelet-rea ctive autoantibody without IgG specificity, and her infant was unaffec ted. A total of 95 (15.8%) of the women tested had HLA antibodies alon e, and the majority demonstrated IgG specificity. On follow-up of 62 i nfants born to these women, none had thrombocytopenia; thus HLA antibo dies were not shown to lead to FMAT in this study. Conclusion: The flo w cytometry-based test for platelet antibodies can detect clinically s ignificant maternal antibodies, and it may be that early diagnosis and treatment in utero can enhance outcome in FMAT. A population screenin g program is planned to determine the predictive power of this test, i n addition to its sensitivity, specificity, and efficiency.