Antenatal platelet antibody testing by flow cytometry--results of a pilot study.
BACKGROUND
Maternal platelet antibodies can cause fetomaternal alloimmune thrombocytopenia (FMAT), which has significant mortality and morbidity even in a first pregnancy. Prenatal diagnosis of FMAT has not previously been possible in the first affected pregnancy.


METHODS
Using flow cytometry, a sensitive, inexpensive test for the 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 fetus was found to be affected in utero, and treatment was initiated before successful delivery. Another woman was shown to have a platelet-reactive autoantibody without IgG specificity, and her infant was unaffected. A total of 95 (15.8%) of the women tested had HLA antibodies alone, and the majority demonstrated IgG specificity. On follow-up of 62 infants born to these women, none had thrombocytopenia; thus HLA antibodies were not shown to lead to FMAT in this study.


CONCLUSIONS
The flow cytometry-based test for platelet antibodies can detect clinically significant maternal antibodies, and it may be that early diagnosis and treatment in utero can enhance outcome in FMAT. A population screening program is planned to determine the predictive power of this test, in addition to its sensitivity, specificity, and efficiency.
Pathology Department, King Edward Memorial Hospital for Women, Subiaco, Western Australia.
L R
LR
Marshall
F E
FE
Brogden
T S
TS
Roper
A L
AL
Barr
D000906:Antibodies / Q000032:analysis; D000918:Antibody Specificity; D016824:Antigens, Human Platelet / Q000276:immunology*; D001792:Blood Platelets / Q000276:immunology; D005260:Female; D005434:Flow Cytometry / Q000379:methods*; D005453:Fluorescence; D005500:Follow-Up Studies; D006680:HLA Antigens / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000737:chemistry / Q000276:immunology; D007518:Isoantibodies / Q000032:analysis*; D010865:Pilot Projects; D010920:Placenta / Q000276:immunology; D011247:Pregnancy / Q000276:immunology*; D011961:Receptors, Fc / Q000276:immunology / Q000502:physiology; D015203:Reproducibility of Results
D000906:Antibodies; D016824:Antigens, Human Platelet; D006680:HLA Antigens; D007074:Immunoglobulin G; D007518:Isoantibodies; D011961:Receptors, Fc