Background: Neonatal alloimmune thrombocytopenia (NAIT) is in most cases due to pregnant women with HPA–1b platelet phenotype producing antibodies to HPA–1a platelets of the fetus, which may lead to intracranial haemorrhage with subsequent death or life–long morbidity. The availability of sensitive, reliable, straightforward, and inexpensive assays would enable large–scale screening in pregnancy and may help avoid NAIT. Methods: A recently developed enzyme–linked immunosorbent assay (ELISA) was produced in kit form incorporating modified reagents and enabling distribution to 21 international Platelet Immunology and Blood Centres (see Acknowledgments). The kits were assessed using anticoagulated whole–blood samples stored up to 10 weeks at 4°C. Each centre tested its own blood samples most of which had been previously typed by established assays. Results: Of the 152 samples that were tested, all 31 HPA–1b phenotypes were correctly identified by the kit. The respective mean ± standard deviation of the specific absorbances of HPA–1b and HPA–1a samples were: 0.52±0.15 and 0.12±0.06 (p<0.0005). In addition, the modified ELISA showed 100% concordance with PCR–SSP in the phenotyping of 93 donors. Finally, a comparison between freshly prepared and stored kits showed that the kit was stable for at least 2 years at 4°C. Conclusions: The international trial showed that the modified whole–blood ELISA kit is very well suited for wide–scale screening in pregnancy. Moreover, the ELISA kit could be used for large–scale phenotyping of blood donors, with HPA–1b–typed individuals getting invited to become apheresis platelet donors for patients with NAIT.

1.
Dreyfus M, Kaplan C, Verdy E, Schlegel N, Durand–Zaleski I, Tchernia G, the Immune Thrombocytopenia Working Group: Frequency of immune thrombocytopenia in newborns: A prospective study. Blood 1997;89:4402– 4406.
2.
Williamson LM, Hackett GA, Rennie JM, Palmer CR, Maciver C, Hadfield R, Hughes D, Jobson S, Ouwehand W: The natural history of fetomaternal alloimmunization to the platelet–specific antigen HPA–1a (PlA1, Zwa) as determined by antenatal screening. Blood 1998;92: 2280–2287.
3.
Kaplan C, Morel–Kopp MC, Clemenceau S, Daffos F, Forestier F, Tchernia G: Fetal and neonatal alloimmune thrombocytopenia: Current trends in diagnosis and therapy. Transfus Med 1992;2:265–271.
4.
Whifield CR, Raafat A, Urbaniak SJ: Underreporting of mortality from Rh (D) haemolytic disease and its implications. Br Med J 1997; 315:1504–1505.
5.
Bessos H, Mirza S, McGill A, Williamson LM, Hadfield R, Murphy WG: A whole blood assay for platelet HPA1 (PLA1) phenotyping applicable to large–scale screening. Br J Haematol 1996;92:221–225.
6.
Bessos H, Goldschmedding R, von dem Borne AKR, Atkinson A, Murphy WG: The development of a simple and quick enzyme–linked immunosorbent assay for anti–HPA1a (PLA1) antibodies. Thromb Res 1993;69:395–400.
7.
Cavanagh G, Dunn AN, Chapman CE, Metcalfe P: HPA genotyping by PCR sequence–specific priming (PCR–SSP): A streamlined method for rapid routine investigations. Transfus Med 1997;7:41–45.
8.
Griffin HM, Ouwehand WH: A human monoclonal antibody specific for the leucine–33 (PLA1, HPA–1a) form of platelet glycoprotein IIIa from a V gene phage display library. Blood 1995;86:4430–4436.
9.
Dobson B, Middleton S: Paying to care: The cost of childhood disability. York Publishing Services, York 1998.
10.
Durand–Zaleski I, Schlegel N, Blum–Boisgard C, Uzan S, Dreyfus M, Kaplan C: Screening primiparous women and newborns for fetal/neonatal alloimmune thrombocytopenia: A prospective comparison of effectiveness and costs. Am J Perinatol 1996;13:423–431.
1999
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