CPT® Code 81106

Human Platelet Antigen 2 genotyping (HPA-2), GP1BA (glycoprotein Ib [platelet], alpha polypeptide [GPIba]) (eg, neonatal alloimmune thrombocytopenia [NAIT], post-transfusion purpura), gene analysis, common variant, HPA-2a/b (T145M)

The CPT® Code 81106 pertains to the gene analysis for Human Platelet Antigen 2 (HPA-2) genotyping, specifically focusing on the GP1BA gene, which encodes the glycoprotein Ib alpha polypeptide. This analysis is particularly relevant in the context of neonatal alloimmune thrombocytopenia (NAIT) and post-transfusion purpura, both of which are conditions associated with platelet alloantigens. The HPA-2a/b allele variants are identified through this testing, which is crucial for understanding the genetic factors that contribute to these conditions. Platelet alloantigens arise from single nucleotide polymorphisms (SNPs) in the genes responsible for coding platelet membrane glycoproteins, leading to variations that can affect platelet function and immune response. The gene analysis may be utilized in various clinical scenarios, including the identification of HPA-2 variants in symptomatic neonates, screening for fetal alloimmunization during pregnancy, and assessing the risk for NAIT in future pregnancies or post-transfusion purpura. NAIT is a serious condition that occurs when maternal IgG antibodies cross the placenta and target paternally derived alloantigens present on fetal platelets, potentially leading to severe complications such as thrombocytopenia and intracranial hemorrhage. On the other hand, post-transfusion purpura is characterized by significant bleeding that occurs 5 to 10 days after a platelet transfusion containing incompatible HPA or platelet-specific antigens. 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 presence of specific allele variants through fluorescence observation.