CPT® Code 81110

1. Indications

The Human Platelet Antigen 6 genotyping (HPA-6w) test is indicated for several specific clinical scenarios, particularly related to platelet-related disorders. The following conditions warrant the use of this gene analysis:

• Neonatal Alloimmune Thrombocytopenia (NAIT) - This condition occurs when maternal IgG antibodies cross the placenta and target paternally derived alloantigens on fetal platelets, leading to severe thrombocytopenia and potential complications such as intracranial hemorrhage.
• Post-Transfusion Purpura - This condition is characterized by severe bleeding that occurs 5-10 days after a platelet transfusion containing incompatible HPA or platelet-specific antigens, necessitating the identification of HPA-6 variants to assess risk.
• Fetal Alloimmunization Screening - The test may be performed during pregnancy to screen for fetal alloimmunization, which can inform management strategies to protect both maternal and fetal health.
• Maternal Risk Assessment for Future Pregnancies - Identifying HPA-6 variants can help assess the risk of NAIT in future pregnancies, allowing for appropriate monitoring and intervention.

2. Procedure

The procedure for Human Platelet Antigen 6 genotyping involves several critical steps to ensure accurate identification of the HPA-6 variants. The following procedural steps are outlined:

• Sample Collection - Blood, amniotic fluid, or cultured amniocytes are collected as the primary samples for analysis. Each sample type is obtained through specific, separately reportable procedures, ensuring that the correct specimen is used for testing.
• DNA Extraction - Once the samples are collected, DNA is extracted from the cells present in the samples. This step is crucial as it prepares the genetic material for subsequent analysis.
• Multiplex Polymerase Chain Reaction (PCR) - The extracted DNA undergoes multiplex PCR, a technique that allows for the simultaneous amplification of multiple target sequences. This step is essential for detecting the specific alleles associated with the HPA-6 variants.
• Allele-Specific Primer Extensions - Following PCR amplification, allele-specific primer extensions are performed. This technique utilizes primers that are designed to bind specifically to the target alleles, allowing for precise identification of the HPA-6a/b variants.
• Fluorescence Observation - The final step involves fluorescence observation, where the results of the allele-specific extensions are analyzed. This step confirms the presence of the HPA-6 variants based on the fluorescence signals generated during the process.

3. Post-Procedure

After the completion of the Human Platelet Antigen 6 genotyping procedure, the following post-procedure considerations are important:

Results from the gene analysis are typically reviewed and interpreted by qualified healthcare professionals. The findings can provide critical information regarding the presence of HPA-6 variants, which can influence clinical management decisions for both the mother and the neonate. In cases of identified alloimmunization, appropriate monitoring and interventions may be initiated to mitigate risks associated with NAIT or post-transfusion purpura. Additionally, healthcare providers may discuss the implications of the results with the patient, including potential risks for future pregnancies and the need for further testing or monitoring.