CPT 81109 HPA‑5 Genetic Test Reimbursement | OpenPayer

Summary & Overview

CPT 81109: HPA-5 (K505E) Genetic Analysis

CPT code 81109 represents a molecular diagnostic laboratory test that analyzes the HPA–5 (K505E) alleles to determine platelet antigen status. This genetic analysis has clinical relevance for transfusion medicine, platelet compatibility assessment, and certain prenatal scenarios where fetal platelet antigen typing may inform clinical decisions. Nationally, such targeted genetic tests contribute to precision transfusion practices and perinatal risk assessment.

Key payers included in the coverage discussion are Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of the code’s clinical context, how and where the test is typically performed, and the practical implications for laboratory services. The publication also summarizes benchmarking and coverage considerations, coding and billing basics, and common clinical scenarios in which CPT code 81109 is used.

This resource is intended to provide a clear, national-level briefing on the purpose of CPT code 81109, the clinical settings in which the test is ordered, and the types of information stakeholders should expect when evaluating laboratory genetic testing for HPA–5 (K505E). Data not available in the input will be noted where applicable.

AetnaBlue Cross Blue ShieldCigna HealthUnitedHealthcareMedicareCPT 81109HPA-5K505Emolecular diagnosticsgenetic testinglaboratory servicestransfusion medicineprenatal testingtechnical component

Billing Code Overview

CPT code 81109 describes a laboratory molecular diagnostic test that analyzes the genes for the two common alleles of Human Platelet Antigen 5 (HPA–5), also known as K505E, using a biological specimen such as blood or amniotic fluid. The procedure involves technical laboratory work to identify allele variants relevant to platelet antigen status.

Service type: Molecular diagnostic genetic test (technical component)
Typical site of service: Clinical laboratory or reference molecular diagnostics laboratory; specimen collection may occur in outpatient phlebotomy settings or obstetric care settings for amniotic fluid specimens.

Clinical & Coding Specifications

Clinical Context

A typical patient is a pregnant woman or an adult being evaluated for alloimmune thrombocytopenia risk or transfusion compatibility. A prenatal obstetrician orders 81109 when a patient has a prior history of neonatal alloimmune thrombocytopenia (NAIT), unexplained fetal thrombocytopenia, a previous infant with intracranial hemorrhage, or when the partner’s or fetus’s platelet antigen status is needed for risk assessment. The clinical workflow begins with collection of a maternal peripheral blood sample (or amniotic fluid when fetal testing is indicated) and submission to a molecular diagnostics laboratory. The laboratory analyst performs DNA-based genotyping to determine the allelic variants of Human Platelet Antigen 5 (HPA–5, K505E). Results are reported to the ordering clinician and used to counsel regarding recurrence risk, guide monitoring in pregnancy, plan for peripartum management, and inform transfusion or platelet selection decisions for the mother or neonate.

Coding Specifications

Modifier	Description	When to Use
`11`	Normal, expected performance of the service	Use when `81109` is performed without unusual circumstances and billing as primary service.

CPT 81271: Huntingtin (HTT) Gene Expanded Allele Detection

CPT-81183-ATXN10-GENE-EXPANDED-ALLELE-DETECTION

CPT 81183: ATXN10 Expanded Allele Detection

CPT-81362-HBB-FAMILIAL-VARIANT-TESTING

CPT 81362: Familial Variant Testing of HBB Gene

CPT-81189-CSTB-GENE-SEQUENCING-TECHNICAL-COMPONENT

CPT 81189: Full CSTB Gene Sequencing, Technical Component

CPT-81237-EZH2-VARIANT-ANALYSIS-CODON-646

CPT 81237: EZH2 Variant Analysis (codon 646)

CPT-81272-PARTIAL-KITT-GENE-SEQUENCE-ANALYSIS

CPT 81272: KIT Gene Partial Sequence Analysis, Technical Component

CPT-81338-MPL-GENE-VARIANT-ANALYSIS-MPN

CPT 81338: MPL Gene Variant Analysis for Myeloproliferative Neoplasms

CPT-81252-GJB2-FULL-GENE-SEQUENCING

CPT 81252: Full Gene Sequencing of GJB2 (Connexin 26)

CPT-81285-FRATAXIN-FXN-GENE-REPEAT-CHARACTERIZATION

CPT 81285: FXN (Frataxin) Gene Repeat Characterization

CPT-81324-PMP22-DELETION-DUPLICATION-ANALYSIS

CPT 81324: PMP22 Deletion/Duplication Analysis

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Taxonomy Code	Specialty	Notes
`0000A`	Clinical Molecular Genetics Laboratory	Molecular diagnostics labs perform `81109` testing; local coding systems will vary.
`0000B`	Pathology - Clinical Molecular Pathology	Pathology departments that manage molecular testing and result interpretation.
`0000C`	Obstetrics & Gynecology	Ordering providers for prenatal risk assessment and management of alloimmune thrombocytopenia.
`0000D`	Maternal-Fetal Medicine	Specialists who order fetal platelet antigen testing for high-risk pregnancies.
`0000E`	Transfusion Medicine/Immunohematology	Specialists coordinating platelet selection and transfusion management based on HPA genotypes.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`D69.5`	Secondary thrombocytopenia	Evaluated when maternal or fetal thrombocytopenia is identified and HPA genotyping helps determine alloimmune causes.
`O36.5XX0`	Maternal care for known or suspected fetal abnormality and damage, unspecified trimester	Used when fetal platelet antigen testing is ordered as part of fetal abnormality assessment (e.g., suspected fetal thrombocytopenia).
`O36.5920`	Maternal care for known or suspected fetal abnormality, suspicion of genetic condition, first trimester	Applied when prenatal genotyping for platelet antigens is sought to assess fetal risk.
`Z36.0`	Encounter for antenatal screening for chromosomal anomalies (used as prenatal screening visit code)	Used when HPA genotyping is part of targeted prenatal screening after prior affected pregnancy.
`Z39.2`	Encounter for routine postpartum follow-up following delivery	Postnatal genotyping may be performed to clarify neonatal thrombocytopenia etiology and guide future pregnancy counseling.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`81479`	Unlisted molecular pathology procedure	Used when a specific genetic test does not have an assigned code; sometimes used for novel or expanded platelet antigen panels alongside `81109`.
`88237`	Flow cytometry, DNA analysis, probe-based (for platelet antigen surface testing)	May be used when platelet antigen expression testing is performed by flow cytometry rather than genotyping; complementary to `81109` when phenotype confirmation is required.
`36415`	Collection of venous blood by venipuncture	Often performed immediately prior to `81109` specimen submission for DNA-based HPA–5 testing.
`0000F`	Maternal cell-free DNA fetal testing (placeholder)	In workflows where fetal genotyping is pursued noninvasively or via amniocentesis, relevant prenatal molecular tests may be ordered in coordination with `81109` results.
`89240`	Amniotic fluid genetic studies (processing)	When fetal testing for HPA alleles is performed on amniotic fluid, specimen processing and genetic analysis codes are part of the workflow.

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