HPA‐1a antibody potency and bioactivity do not predict severity of fetomaternal alloimmune thrombocytopenia

Abstract

Neither severe thrombocytopenia nor ICH in HPA-1a-alloimmunized pregnancies can be predicted with sufficient sensitivity and specificity for clinical application from maternal anti-HPA-1a potency or bioactivity.

A prospective study of maternal anti-HPA 1a antibody level as a potential predictor of alloimmune thrombocytopenia in the newborn

“…Recently, Ghevaert et al 10 published the results of a retrospective study in which no correlation could be found between the maternal anti-HPA 1a antibody level and platelet count in the neonates. The explanation for the divergence between their results and ours may be differences in selection criteria.…”

“…[4][5][6][7] A correlation was also found in two retrospective studies, 8,9 whereas one other retrospective study did not find such a relationship. 10 In a recent trial, we documented that identification of women with anti-HPA 1a antibodies, close clinical follow-up during pregnancy, elective Cesarean section and transfusion of compatible platelets to neonates with severe thrombocytopenia, reduce NAIT-related morbidity and mortality. 11 The main purpose of this study was to describe the natural course of HPA 1a alloimmunity by recording maternal anti-HPA 1a antibody levels longitudinally throughout pregnancy and after delivery.…”

Developing recombinant HPA-1a–specific antibodies with abrogated Fcγ receptor binding for the treatment of fetomaternal alloimmune thrombocytopenia

“…In hemolytic disease of the newborn, clinically significant hemolysis is associated with CL responses of more than 30% of the maximum response obtained with a control antibody (48). With HPA-1a antibodies, there appears to be no correlation between either in vitro potency or monocyte CL responses to maternal anti-HPA-1a and fetal platelet count (53). Therefore, at this stage it would be difficult to estimate by how much maternal antibodies would have to be blocked to generate a clinically significant effect.…”

“…The potency of each clinical sample and both polyclonal IgG preparations was measured using the international anti-HPA-1a potency standard 03/152 (100 IU/ml) (National Institute for Biological Standards and Control) (53,58).…”

Reconsidering fetal and neonatal alloimmune thrombocytopenia with a focus on screening and prevention

“…More recently, maternal anti-HPA-1a antibody level during the pregnancy has been claimed to be a better predictive factor, although the predictive value has been questioned [48]. Williamson et al reported a correlation between antibody titre in the last trimester and severity of thrombocytopenia [10].…”