Ordering Recommendation

Assess risk for fetal and neonatal alloimmune thrombocytopenia. May be ordered for parental, fetal, or neonatal genotyping.

Mnemonic
HPA-1 GENO
Methodology

Polymerase Chain Reaction/Fluorescence Monitoring

Performed

Mon, Thu

Reported

7-14 days

New York DOH Approval Status
This test is New York DOH approved.
Specimen Required
Patient Preparation
Collect

Fetal Specimen: Amniotic fluid OR 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 Note): Lavender (EDTA), Pink (K2EDTA), or Yellow (ACD Solution A or B).
Parental Specimen:
Lavender (EDTA).

Specimen Preparation

Amniotic Fluid: Transport 10 mL unspun fluid. (Min: 5 mL)
Cultured Amniocytes:
Transport two T-25 flasks at 80 percent confluency filled with culture media. Backup cultures must be retained at 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
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 1 Genotyping (HPA-1):
Characteristics:
Spontaneous fetal intracranial bleeding may occur in 20 percent of pregnancies affected with severe perinatal alloimmune thrombocytopenia (PAT); 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:
HPA-1 (ITGB3, GPIIIa) c.176T>C, p.L59P
Clinical Sensitivity:
80 percent in Caucasians, unknown in other ethnicities.
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. Diagnostic errors can occur due to rare sequence variations.
Informed consent:
Recommended; forms are available at https://www.aruplab.com.

Compliance Category

Laboratory Developed Test (LDT)

Note

Maternal specimen is recommended for proper test interpretation if contamination of the fetal specimen from the mother is suspected. Order Maternal Cell Contamination.

Hotline History
N/A
CPT Codes

81105

Components
Component Test Code* Component Chart Name LOINC
3001173 Platelet Antigen 1 Genotyping
3001182 Platelet Antigen 1 Interpretation
3001183 Platelet Antigen 1 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
  • HPA1 genotyping
Platelet Antigen 1 Genotyping (HPA-1)