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.
Marshall
L R
LR
Pathology Department, King Edward Memorial Hospital for Women, Subiaco, Western Australia.
Brogden
F E
FE
Roper
T S
TS
Barr
A L
AL
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