Platelet alloantibodies play a important role in neonatal alloimmune thrombocytopenia
HPA (human platelet antigens) are known to be involved in neonatal allo-immunethrombocytopenia (NAIT). For the detection of platelet antibodies, we developed MPHA (mixed passive hemagglutination) method for detecting anti-platelet antibodies.
Using MPHA test, we screened 20,333 sera from pregnant women (28-30 weeks gestation) and obtained the following results.
(1) Unexpectedly high prevalence of platelet antibodies in 198 sera (0.97%) The specificity of them were as follows,
anti-HPA-5b 168 sera(82, 3%), anti-HPA-4b 27 sera(13, 6%)
anti-HPA-6b 2 sera(1, 0%), anti-Nak-a 5 sera(2, 5%)
anti-HPA-4b+anti-HPA-5b 1 serum(0, 5%).
(2) Five cases of NAIT were due to anti-HPA-5b, two cases of NAIT were due to anti-HPA-4b, and one case was due to anti-HPA-4b and anti-HPA-5b. This is the first prospective study on neonatal alloimmune thrombocytemia.