Platelet Antigen 2 Genotyping (HPA-2)
0051310
Ordering Recommendation
Assess risk for fetal and neonatal alloimmune thrombocytopenia (FNAIT). Test may be ordered for parental or fetal genotyping.
Mnemonic
HPA2
Methodology
Polymerase Chain Reaction/Fluorescence Monitoring
Performed
Mon, Thu
Reported
2-7 days  
New York DOH Approval Status
This test is New York DOH approved.
Specimen Required
Patient Preparation
  
Collect
Fetal Genotyping: Amniotic fluid OR two T-25 flasks at 80 percent confluency of cultured amniocytes. If the client is unable to culture amniocytes, this can be arranged by contacting ARUP Client Services at (800) 522-2787. 
WITH Maternal Cell Contamination Specimen 
(see Remarks)Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).
Parental Genotyping:
Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).  
Specimen Preparation
Amniotic Fluid: Transport 10 mL unspun fluid. (Min: 5 mL)
Cultured Amniocytes:
Fill flasks with culture media. Transport two T-25 flasks at 80 percent confluency of cultured amniocytes filled with culture media. Backup cultures must be retained the client's institution until testing is complete.
Maternal Cell Contamination Specimen:
Transport 3 mL whole blood (Min: 1 mL)
Whole Blood (Parental Genotyping):
Transport 3 mL whole blood. (Min: 1 mL)  
Storage/Transport Temperature
Amniotic fluid: Room temperature.
Cultured Amniocytes:
 CRITICAL ROOM TEMPERATURE. Must be received within 48 hours of shipment due to liability of cells.
Whole Blood or Maternal Cell Contamination Specimen:
Refrigerated.  
Unacceptable Conditions
  
Remarks
Maternal specimen is recommended for proper test interpretation if contamination of the fetal specimen from the mother is suspected. Order Maternal Cell Contamination. Patient History Form is available on the ARUP Web site or by contacting ARUP Client Services.  
Stability
Fetal Specimen: Ambient: 48 hours; Refrigerated: Unacceptable; Frozen: Unacceptable
Whole Blood or Maternal Cell Contamination Specimen:
Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable  
Reference Interval
By report  
Interpretive Data
Background Information for Platelet Antigen 2 Genotyping (HPA-2):
Characteristics:
Spontaneous fetal intracranial bleeding may occur in 20 percent of severe perinatal alloimmune thrombocytopenia (PAT) affected pregnancies; there is a risk of fetal death. Post-transfusion purpura may occur in transfusion recipients with antibodies to a specific platelet antigen.
Incidence:
PAT occurs in 1 in 5000 births.
Inheritance:
For women homozygous for a rare "b" HPA allele with antibodies to the common "a" allele, there is a 50 percent risk a pregnancy will be affected if her partner is heterozygous for the "a" allele and 100 percent risk if her partner is homozygous for the "a" allele.
Cause:
Maternal-fetal HPA incompatibility.
Polymorphism Tested:
Glycoprotein Iba (GPIba) c.482C>T; p.T161M; the common "a" allele is represented by cytosine at position c.482.
Clinical Sensitivity:
Unknown.
Methodology:
PCR followed by fluorescent monitoring.
Analytic Sensitivity and Specificity:
99 percent.
Limitations:
Bloody amniotic fluid specimens may give false-negative results because of maternal cell contamination. Specificity may be compromised by mutations in primer sites. Diagnostic errors can occur due to rare sequence variations.
Informed consent:
Recommended; forms are available at www.aruplab.com.

This test is performed pursuant to an agreement with Roche Molecular Systems, Inc.





See Compliance Statement C: www.aruplab.com/CS
Statement C: The performance characteristics of this test were validated by ARUP Laboratories. The U.S. Food and Drug Administration (FDA) has not approved or cleared this test; however, FDA approval or clearance is currently not required for clinical use of this test. The results are not intended to be used as the sole means for clinical diagnosis or patient management decisions. ARUP is authorized under Clinical Laboratory Improvement Amendments (CLIA) and by all states to perform high-complexity testing.

Counseling and informed consent are recommended for genetic testing. Consent forms are available online.
 
Note
 
CPT Code(s)
81400
Components
Component Test Code*Component Chart Name
0051322Platelet Antigen 2 Genotyping
0051323Platelet Antigen 2 Interpretation
2001321Platelet Antigen 2 Specimen
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
Aliases
  • HPA 2 genotyping