CPT 81108 HPA‑4 Genotyping Reimbursement

CPT code 81108 represents a molecular diagnostic laboratory test that analyzes the two common alleles of Human Platelet Antigen 4 (HPA–4 / R143Q) using specimens such as blood or amniotic fluid. This code captures the technical component of allele-specific genotyping for HPA–4, a test relevant for platelet antigen compatibility, alloimmunization assessment, and perinatal risk evaluation. Nationally, precise coding for specialized genetic tests supports appropriate claims processing, clinical documentation, and surveillance of genetic testing utilization.

Key payers discussed include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of the clinical purpose of the test, typical sites of service, and payer coverage context. The publication also summarizes benchmarks where available, highlights coding and policy considerations affecting reimbursement and claim acceptance, and provides clinical context for use of HPA–4 genotyping in maternal–fetal medicine and transfusion medicine. Data not available in the input regarding specific coverage policies, associated taxonomies, and ICD-10 diagnoses is noted where applicable.

Billing Code Overview

CPT code 81108 describes a laboratory molecular test in which the technical component analyzes the genes of the two common alleles of Human Platelet Antigen 4 (HPA–4), also known as R143Q. The procedure is performed on a biological specimen such as blood or amniotic fluid.

Service type: Molecular genetic testing / technical laboratory analysis
Typical site of service: Clinical laboratory or hospital laboratory; specimens collected in outpatient phlebotomy settings or inpatient settings, and testing performed in a certified diagnostic laboratory.

Clinical Context

A 29-year-old pregnant woman with a prior child affected by neonatal alloimmune thrombocytopenia (NAIT) is referred for maternal HPA genotyping. The obstetrician orders testing to determine fetal risk for HPA‑4 incompatibility after paternal and maternal history suggest a potential HPA mismatch. A blood specimen is collected from the mother (and often the father) and sent to a molecular diagnostic laboratory. The lab analyst performs a targeted genetic assay to detect the two common alleles of Human Platelet Antigen 4 (HPA‑4, also called R143Q) from maternal peripheral blood; in some cases, amniotic fluid or fetal DNA from cell‑free fetal DNA may be analyzed. Results are reported to the ordering obstetrician and a maternal‑fetal medicine specialist to inform antenatal monitoring and peripartum transfusion planning.

Key workflow steps:

Referral and order entry by obstetrician or maternal‑fetal medicine specialist.
Specimen collection (maternal venous blood; optionally paternal blood or amniotic fluid) and appropriate labeling.
Specimen accessioning and extraction of DNA in the molecular laboratory.
Technical performance of the genetic assay by the lab analyst for HPA‑4 alleles (CPT 81108), including controls and quality checks.
Technical result generation (allelic status: homozygous/heterozygous/negative), result verification by laboratory personnel, and transmission of results to the ordering provider.
Clinical interpretation and integration into perinatal care planning by the ordering clinician, including preparation for potential neonatal thrombocytopenia management at delivery.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when billing only the professional component of a paired technical/professional service (rare for purely technical molecular tests).

52 | Reduced services | Use when the service performed is partially reduced or not fully completed.

53 | Discontinued procedure | Use when testing is started but discontinued for reasons beyond provider control (e.g., inadequate specimen identified before completion).

59 | Distinct procedural service | Use to indicate a distinct procedural service when another unrelated service is performed on the same day.

62 | Two surgeons | Use when two qualified providers of the same specialty perform distinct portions of a service (unlikely for this lab test but included if dual surgical involvement relates to specimen procurement).

78 | Unplanned return to OR | Use only when an unplanned return to the operating room is required (not typically applicable to the assay itself).

90 | Reference (outside) laboratory | Use when the specimen is sent to an outside/reference laboratory for analysis.

TC | Technical component | Use when billing only the technical component of the test (common when the lab performs only the technical assay).

QX | CLIA qualified non‑physician laboratory director | Use when testing is performed under a CLIA‑qualified non‑physician director as applicable.

QY | CLIA physician director | Use when testing is performed under a CLIA‑qualified physician director as applicable.

AS | Physician assistant, nurse practitioner, or clinical nurse specialist services | Use when these clinicians furnish a portion of service as allowed by payer policy (rare for lab testing billing).

90 is listed above; duplicate modifier codes are not repeated.

Taxonomy Code	Specialty	Notes
`207RC0000X`	Reproductive Endocrinology & Infertility	Frequently orders prenatal genetic and platelet antigen testing in high‑risk pregnancies.

207Q00000X | Obstetrics & Gynecology | Common ordering specialty for antenatal HPA genotyping.

208M00000X | Maternal-Fetal Medicine | Specialist managing pregnancies at risk for alloimmune conditions such as NAIT.

181400000X | Clinical Laboratory | Laboratories performing molecular genetic testing and reporting CPT 81108.

207L00000X | Pediatrics (Neonatology) | May be involved in peripartum planning and neonatal management when HPA incompatibility is identified.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`O36.592`	Maternal care for (suspected) fetal abdominal and pelvic abnormalities, unspecified trimester	Example maternal‑fetal indication when fetal testing, including genetic evaluations, is performed alongside other fetal assessments.

O36.81 | Maternal care for other known or suspected fetal conditions, not elsewhere classified | General antenatal indication category for specialized fetal testing such as HPA genotyping.

D69.5 | Secondary thrombocytopenia | Relevant when neonatal or maternal thrombocytopenia may be related to alloimmune platelet antigen incompatibility prompting HPA testing.

Z34.90 | Encounter for supervision of normal pregnancy, unspecified trimester | Routine prenatal care diagnosis often present when targeted tests like CPT 81108 are ordered in high‑risk pregnancies.

Z31.430 | Encounter for genetic counseling, prenatal | Frequently accompanies molecular diagnostic testing orders and counseling for alloimmune risk assessment.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`81108`	HPA‑4 (R143Q) genotyping — technical analytic test	Primary procedure: the lab technical assay to detect `HPA‑4` alleles.

81225 | Hemoglobin S, C, D, E mutation analysis; qualitative or quantitative — molecular analysis | Often performed in prenatal or perinatal molecular panels when broader red cell/hemoglobinopathy testing is indicated alongside platelet antigen evaluation.

81479 | Unlisted molecular pathology procedure | Used when a lab performs a molecular test not described by existing CPT codes in conjunction with CPT 81108 for additional or bespoke analyses.

36415 | Collection of venous blood by venipuncture | Specimen collection code commonly billed by phlebotomy services prior to sending the sample for CPT 81108.

88360 | Morphometric analysis (e.g., immunohistochemistry), per specimen | Occasionally used if tissue‑based confirmatory testing or immunophenotyping complements molecular platelet antigen testing in complex cases.

0000F | (Quality measure placeholder) | Quality/reporting codes for lab reporting and results transmission may be used in institutional reporting; not a CPT charge code but appears in workflows for reporting completeness.

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Summary & Overview

CPT 81108: HPA-4 (R143Q) Genotyping, Technical Component