CPT® Code 81105

Human Platelet Antigen 1 genotyping (HPA-1), ITGB3 (integrin, beta 3 [platelet glycoprotein IIIa], antigen CD61 [GPIIIa]) (eg, neonatal alloimmune thrombocytopenia [NAIT], post-transfusion purpura), gene analysis, common variant, HPA-1a/b (L33P)

The CPT® Code 81105 pertains to the gene analysis of Human Platelet Antigen 1 (HPA-1), specifically focusing on the HPA-1a/b allele variant. This genetic testing is crucial for identifying the presence of the HPA-1a/b variant, which is 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 target paternally inherited alloantigens present on the fetal platelets, leading to a significant reduction in platelet count, known as thrombocytopenia. Symptoms of NAIT can manifest as severe thrombocytopenia, intracranial hemorrhage, and various forms of bleeding, including petechiae and visceral hemorrhage. On the other hand, post-transfusion purpura occurs when a patient experiences severe bleeding following a platelet transfusion that contains incompatible HPA or platelet-specific antigens. The HPA-1 a/b allele variants are particularly significant, as they are implicated in approximately 80% of severe NAIT cases within the Caucasian population. 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 affected neonates but also plays a vital role in screening for fetal alloimmunization during pregnancy and assessing the risk for future pregnancies or post-transfusion complications in mothers.