Platelet Immunology Laboratory

Neonatal Alloimmune Thrombocytopenia Evaluation (NATP)

• Test Code: 3670-00
• CPT Codes: 86022x2, 86023, 83912, 86807, 86021, 83890x2, (83892, 83984, 83898)x6, 83912

Thrombocytopenia in the newborn occurs when maternal platelet antibodies cross the placenta, bind to fetal platelets, and the antibody-coated platelets are rapidly cleared from fetal circulation. Sensitization occurs when an incompatible platelet antigen is inherited from the father and a maternal antibody is formed in response to this antigen. Unlike erythroblastosis fetalis, NATP can occur in the first-born. NATP is rare, occurring in 1 in 2,000-5,000 births. Most NATP cases are due to the platelet specific antigen PIAl (HPA-1a), but other platelet specific antigens have also been implicated in this disorder.

Positive crossmatch results between the maternal plasma and paternal platelets, and platelet antigen discrepancies between paternal and maternal platelets are indicative of NATP. In some cases, a discrepancy between the maternal and paternal platelet antigens cannot be identified but the test results (crossmatch results between the mother's plasma and the father's platelets) are unequivocally positive. This may indicate the presence of a new platelet antigen and is an area of current research.

• Tests Performed: Platelet antibody crossmatch testing of maternal plasma with paternal platelets by Flow cytometry, Platelet antigen typing of both parents' platelets by DNA (PCR) and HLA antibody identification Class I, PAK-12G or MAIPA (if warranted).
• Test Types: Direct and Indirect
• Samples Required: In addition to the below sample requirements, the Platelet Immunology Supervisor must be contacted to discuss the patient's clinical history. The supervisor can be reached at 206-292-6542.

• Analytic Time: 1 Day for Serological Results; 5 Days for additional results
• Send whole blood, room temperature
• Refer to Ordering Information page for submission and transporting requirements