CPT® Code 81107

Human Platelet Antigen 3 genotyping (HPA-3), ITGA2B (integrin, alpha 2b [platelet glycoprotein IIb of IIb/IIIa complex], antigen CD41 [GPIIb]) (eg, neonatal alloimmune thrombocytopenia [NAIT], post-transfusion purpura), gene analysis, common variant, HPA-3a/b (I843S)

The CPT® Code 81107 refers to the gene analysis for Human Platelet Antigen 3 (HPA-3) genotyping, specifically targeting the ITGA2B gene, which encodes the integrin alpha 2b, a component of the platelet glycoprotein IIb/IIIa complex. This analysis is crucial for identifying the HPA-3a/b allele variants that are associated with conditions such as neonatal alloimmune thrombocytopenia (NAIT) and post-transfusion purpura. NAIT is a serious condition that arises when maternal IgG antibodies cross the placenta and attack the paternally derived alloantigens present on fetal platelets, leading to severe thrombocytopenia and potential complications such as intracranial hemorrhage. Post-transfusion purpura, on the other hand, occurs when a woman receives a platelet transfusion that contains incompatible HPA or platelet-specific antigens, resulting in severe bleeding episodes typically occurring 5 to 10 days post-transfusion. The identification of HPA-3 variants is particularly significant as these variants are found in approximately 1% of cases involving NAIT and post-transfusion purpura. The testing process involves obtaining samples from blood, amniotic fluid, or cultured amniocytes, which are then analyzed using multiplex polymerase chain reaction (PCR) techniques to detect the specific allele variants through fluorescence observation. This gene analysis not only aids in diagnosing symptomatic neonates but also plays a vital role in screening for fetal alloimmunization during pregnancy and assessing the maternal risk for NAIT in future pregnancies or post-transfusion complications.