A Non-Invasive Strategy for Neonatal Alloimmune Thrombocytopenia Diagnosis: Newborn Platelet Genotyping with Buccal Swabs

Neonatal alloimmune thrombocytopenia results from the maternal immune response against fetal-specific antigens inherited from the father. The diagnosis is ascertained only when the maternal alloantibody and the offending antigen present in the newborn are identified. Up until now most laboratories perform DNA extraction for neonatal genotyping from newborn blood samplings. In order to avoid such an invasive procedure, two protocols of DNA extraction from buccal swabs were developed: a manual protocol using the QIAamp mini blood kit (Qiagen), and an automated procedure with the MagNA Pure Compact instrument (Roche). Both EDTA-blood and buccal swabs from thrombocytopenic newborns were genotyped manually (14 samples), automatically (15 samples) or both manually and automatically (two samples). Human Platelet Antigen (HPA) genotyping was performed using the BeadChip assay (BioArray, Immucor). Concordant genotypings were obtained for all samples except for one swab with the manual method. The automated DNA extraction from newborn buccal swabs with the MagNA Pure Compact instrument was chosen as the first-line strategy, with a significant gain of time in processing buccal swabs.