Improved Assay for Detection of Platelet‐Specific PlA1 Antibodies in Neonatal Alloimmune Thrombocytopenia

A technique is described which permits the detection of platelet-specific, noncomplement-fixing ("blocking') PlA1 antibodies in serologically negative sera of mothers from children suffering from neonatal alloimmune thrombocytopenia. The technique consists of (1) antibody enrichment in eluates prepared from maternal serum and PlA1-positive platelets, and (2) quantitation of antibodies in eluates by the platelet radioactive anti-IgG test. With this assay, PlA1 antibodies were demonstrated in 6 out of 7 maternal sera, and anti-A antibodies in one. It proved valuable also for longitudinal studies for periods up to 30 months after delivery.