Background
Maternal anti–human leukocyte antigen (HLA) Class I is commonly detected alongside anti–human platelet antigen (HPA)‐1a in fetal and neonatal alloimmune thrombocytopenia (FNAIT). Little is known regarding whether the presence of anti‐HLA Class I may exert an additive effect on the risk and severity of FNAIT.
Methods and Materials
We reanalyzed samples originally collected as part of a large Norwegian screening study on FNAIT during 1995‐2004. This study identified and managed 170 pregnancies where the mother was HPA‐1a negative and had detectable anti‐HPA‐1a during pregnancy. Maternal samples from 166 of these pregnancies were rescreened for anti‐HLA Class I, revealing 111 (67%) that were antibody positive. Various regression models were used to assess if and how maternal anti‐HLA Class I influenced the neonatal platelet count.
Results and Conclusions
Unadjusted neonatal platelet counts and the frequency of neonatal thrombocytopenia was not significantly affected by the presence of anti‐HLA Class I alongside anti–HPA‐1a, but results from regression analyses revealed a possible increased risk when the mother was nulliparous. These results warrant further investigation.