CPT® Code 81111

Official Description

Human Platelet Antigen 9 genotyping (HPA-9w), 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-9a/b (V837M)

Common Language Description

The CPT® Code 81111 refers to the gene analysis for Human Platelet Antigen 9 (HPA-9) genotyping, specifically targeting the ITGA2B gene, which encodes the integrin alpha 2b, a component of the platelet glycoprotein IIb/IIIa complex, also known as antigen CD41. This analysis is particularly relevant in the context of conditions such as neonatal alloimmune thrombocytopenia (NAIT) and post-transfusion purpura, both of which are associated with platelet alloantigens. The test aims to identify specific variants of the HPA-9 allele, namely HPA-9a and HPA-9b, which are determined by a common variant known as V837M. Gene analysis for HPA-9 variants is crucial for diagnosing and managing conditions where maternal antibodies may target fetal platelets, leading to significant clinical consequences. In NAIT, maternal IgG antibodies can cross the placenta and attack the paternally inherited alloantigens present on the fetal platelets, resulting in severe thrombocytopenia and potential complications such as intracranial hemorrhage, petechiae, and visceral hemorrhage. Similarly, post-transfusion purpura can occur when a woman receives a platelet transfusion that contains incompatible HPA or platelet-specific antigens, leading to severe bleeding episodes typically occurring 5 to 10 days post-transfusion. The analysis can be performed on various sample types, including whole blood, amniotic fluid, or cultured amniocytes, and utilizes advanced techniques such as multiplex polymerase chain reaction (PCR) with allele-specific primer extensions and fluorescence observation to detect the presence of these genetic variants. This testing is essential for identifying at-risk neonates, screening for fetal alloimmunization during pregnancy, and assessing maternal risk for future pregnancies or transfusion-related complications.

1. Indications

The Human Platelet Antigen 9 genotyping (HPA-9w) test is indicated for several specific clinical scenarios, particularly related to conditions that involve platelet alloantigens. The following are the primary indications for performing 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.
Post-Transfusion Purpura - This condition arises when a woman receives a platelet transfusion containing incompatible HPA or platelet-specific antigens, resulting in severe bleeding episodes that typically occur 5 to 10 days after the transfusion.
Fetal Alloimmunization Screening - The test may be used to screen for fetal alloimmunization during pregnancy, helping to identify at-risk neonates.
Maternal Risk Assessment - The analysis can assess maternal risk for NAIT in future pregnancies or post-transfusion purpura, providing valuable information for clinical management.

2. Procedure

The procedure for Human Platelet Antigen 9 genotyping involves several key steps to ensure accurate identification of the HPA-9 variants. The following outlines the procedural steps:

Sample Collection - Blood, amniotic fluid, or cultured amniocytes are collected as the biological samples for testing. Each sample type is obtained through separate reportable procedures, ensuring that the correct specimen is used for analysis.
DNA Extraction - Once the samples are collected, DNA is extracted from the cells present in the samples. This step is crucial for isolating the genetic material needed for the subsequent analysis.
Multiplex Polymerase Chain Reaction (PCR) - The extracted DNA undergoes multiplex PCR, a technique that allows for the amplification of specific DNA sequences associated with the HPA-9 alleles. This step is essential for generating sufficient quantities of DNA for analysis.
Allele-Specific Primer Extensions - Following amplification, allele-specific primer extensions are performed to selectively extend primers that bind to the target HPA-9 variants. This step enhances the specificity of the test, allowing for accurate identification of the HPA-9a/b alleles.
Fluorescence Observation - The final step involves fluorescence observation, where the results of the allele-specific extensions are analyzed. This allows for the determination of the presence of HPA-9a or HPA-9b variants in the sample.

3. Post-Procedure

After the completion of the HPA-9 genotyping procedure, the results are interpreted to determine the presence of HPA-9 variants. Clinicians will use this information to guide further management of the patient, particularly in cases of NAIT or post-transfusion purpura. It is important to monitor the patient for any symptoms related to these conditions, such as thrombocytopenia or bleeding episodes. Additionally, the results may inform decisions regarding future pregnancies and transfusion strategies to mitigate risks associated with incompatible platelet antigens. Follow-up consultations may be necessary to discuss the implications of the test results and to plan appropriate care based on the findings.

Short Descr	HPA-9 GENOTYPING
Medium Descr	HPA-9 GENOTYPING GENE ANALYSIS COMMON VARIANT
Long Descr	Human Platelet Antigen 9 genotyping (HPA-9w), 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-9a/b (V837M)
Status Code	Statutory Exclusion (from MPFS, may be paid under other methodologies)
Global Days	XXX - Global Concept Does Not Apply
PC/TC Indicator (26, TC)	9 - Not Applicable
Multiple Procedures (51)	9 - Concept does not apply.
Bilateral Surgery (50)	9 - Concept does not apply.
Physician Supervisions	09 - Concept does not apply.
Assistant Surgeon (80, 82)	9 - Concept does not apply.
Co-Surgeons (62)	9 - Concept does not apply.
Team Surgery (66)	9 - Concept does not apply.
Diagnostic Imaging Family	99 - Concept Does Not Apply
CLIA Waived (QW)	No
APC Status Indicator	Service Paid under Fee Schedule or Payment System other than OPPS
Type of Service (TOS)	5 - Diagnostic Laboratory
Berenson-Eggers TOS (BETOS)	none
MUE	1

90	Reference (outside) laboratory: when laboratory procedures are performed by a party other than the treating or reporting physician or other qualified health care professional, the procedure may be identified by adding modifier 90 to the usual procedure number.