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CPT 81377: HLA Class II Allele Group Typing, Low/Intermediate Resolution

CPT code 81377 designates a laboratory technical procedure for low- or intermediate-resolution assessment of human leukocyte antigen (HLA) genes for one Class II antigen equivalent (allele group). This assay supports clinical decisions in transplantation compatibility, immune-mediated disease evaluation, and certain pharmacogenomic contexts, making it a clinically significant molecular diagnostic billed under laboratory services nationally. Coverage and payment for HLA typing affect hospital and outpatient laboratories, transplant programs, and clinical genetic services.

Key payers discussed include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of coverage considerations and common billing practices across major national payers, plus context on clinical utility and service settings. The report outlines typical service lines, sites of service, and the technical nature of the assay. It also summarizes common modifiers observed in billing (input provided) and notes when specific payer policy or coding guidance is not available.

This publication helps laboratory administrators, billing professionals, and clinical program leaders understand what CPT code 81377 represents, how it is used in practice, and where to look for payer-specific policy details. Data not available in the input is identified where applicable; the focus remains on national-level clinical and billing context rather than state-specific rules.

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Billing Code Overview

CPT code 81377 describes a laboratory technical procedure for low- or intermediate-resolution assessment of human leukocyte antigen (HLA) genes for one Class II antigen equivalent (an allele group of interest). The service is a molecular/genetic laboratory test performed by a laboratory analyst to identify HLA Class II allele groups that may be associated with specific conditions.

Service type: Laboratory — molecular/genetic testing (HLA typing)

Typical site of service: Clinical laboratory or specialized molecular diagnostics laboratory (ambulatory or hospital-based lab setting)

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CPT 81377: HLA Class II Allele Group Typing, Low/Intermediate Resolution

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Billing Code Overview

Service type: Laboratory — molecular/genetic testing (HLA typing)

Typical site of service: Clinical laboratory or specialized molecular diagnostics laboratory (ambulatory or hospital-based lab setting)

Clinical & Coding Specifications

Clinical Context

A 32-year-old patient with a history of recurrent pregnancy loss is evaluated by a maternal-fetal medicine specialist. The clinician orders human leukocyte antigen (HLA) low- or intermediate-resolution typing for one Class II antigen equivalent to assess allele group compatibility associated with immune-mediated reproductive issues. A phlebotomy technician collects a blood specimen at an outpatient laboratory. The specimen is accessioned and processed in the molecular immunogenetics lab. The lab analyst performs 81377 to determine the allele group for the specified Class II locus (for example, an HLA-DRB1 allele group) using validated low- or intermediate-resolution molecular methods. Results are reported to the ordering clinician, who integrates the HLA allele group information with clinical data for counseling and management decisions such as donor selection or risk assessment. Typical site of service: outpatient hospital laboratory or independent clinical molecular laboratory. Service type: molecular immunogenetics laboratory technical analysis for targeted Class II HLA allele group testing.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when billing only the professional (interpretation) component if separated from the technical lab work.
`TC`	Technical component	Use when billing only the technical component of the lab test (most common for `81377`).
`59`	Distinct procedural service	Use when this HLA test is a separate, distinct service from other procedures on the same date.
`90`	Reference (outside) laboratory	Use when the testing was referred to an outside reference laboratory.
`91`	Repeat clinical diagnostic test	Use when the same test is repeated on the same patient to confirm results within a short timeframe.
`52`	Reduced services	Use when the test is partially reduced or not performed to full protocol and documentation supports reduction.
`53`	Discontinued procedure	Use when testing began but was discontinued for documented reasons (rare for lab assays).
`59`	Distinct procedural service	Use when the HLA assay is distinct from other billed lab services (listed to emphasize distinctness).
`90`	Reference lab	Use when specimen is sent to an external reference lab for performance of `81377`.
`91`	Repeat test	Use when repeat testing is clinically indicated due to prior indeterminate or discordant result.

Taxonomy Code	Specialty	Notes
207RH0000X	Hematopathology	Pathologists who oversee immunogenetics and HLA testing in clinical labs.
207L00000X	Clinical Pathology	Clinical pathologists directing laboratory testing and interpretation.
207K00000X	Molecular Genetic Pathology	Specialists in molecular diagnostics who validate and supervise HLA molecular assays.
208D00000X	Obstetrics & Gynecology	Ordering clinicians for reproductive immunology indications such as recurrent pregnancy loss.
208000000X	Family Medicine	Primary care or reproductive medicine clinicians who may order targeted HLA testing.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`Z31.430`	Encounter for fertility testing; infertility evaluation female	HLA typing may be ordered during fertility workup when immunologic factors are considered in recurrent implantation failure.
`O26.82`	Maternal care for other specified fetal problems; recurrent pregnancy loss	HLA allele group testing can be used in evaluation of immune-mediated causes of recurrent pregnancy loss.
`Z48.01`	Encounter for change or removal of surgical dressings; not directly related	Data not directly applicable to this procedure but included when present in input.
`Z52.2`	Blood donor status	HLA testing can be relevant for donor matching in selected transfusion or transplant contexts.
`D76.1`	Hemophagocytic lymphohistiocytosis	HLA associations may be explored in complex immune dysregulation workups where targeted HLA testing contributes to diagnosis.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`81377`	HLA typing; low or intermediate resolution for one Class II antigen equivalent (allele group)	The primary technical assay performed by the molecular immunogenetics laboratory to determine an HLA Class II allele group.
`81376`	HLA typing; low or intermediate resolution for one Class I antigen equivalent (allele group)	Performed when Class I allele group information is required in addition to Class II; may be ordered concurrently for comprehensive HLA assessment.
`81479`	Unlisted molecular pathology procedure	Used for molecular tests not specifically described by existing CPT codes when additional specialized HLA analyses are required beyond `81377`.
`88360`	Immunohistochemistry or immunocytochemistry, per specimen; initial single antibody stain	Occasionally used when correlated antigen expression studies are performed on tissue in conjunction with HLA testing in complex cases.
`80500`	Tissue typing; serologic testing, HLA-A, -B, -C, -DR, -DQ (each antigen) — historical/alternative methods	Historical or alternate methodology codes that may appear in legacy workflows where serologic typing complements molecular HLA results.

CPT 81370: HLA Class I and II Low/Intermediate-Resolution Molecular Typing

CPT-81371-HLA-A-B-DRB1-LOW-INTERMEDIATE-RESOLUTION-TYPING

CPT 81371: HLA-A, HLA-B, HLA-DRB1 Low/Intermediate Resolution Typing

CPT-81372-HLA-CLASS-I-LOW-INTERMEDIATE-RESOLUTION-TYPING

CPT 81372: HLA Class I Low/Intermediate-Resolution Molecular Typing

CPT-81373-HLA-CLASS-I-LOW-INTERMEDIATE-RESOLUTION

CPT 81373: HLA Class I Low/Intermediate Resolution Molecular Test

CPT-81374-HLA-CLASS-I-LOW-INTERMEDIATE-RESOLUTION

CPT 81374: HLA Class I Low/Intermediate-Resolution Testing

CPT-81375-HLA-CLASS-II-LOW-INTERMEDIATE-RESOLUTION-TYPING

CPT 81375: HLA Class II Low/Intermediate-Resolution Molecular Typing

CPT-81376-HLA-CLASS-II-TYPING-LOW-INTERMEDIATE-RESOLUTION-TECHNICAL

CPT 81376: HLA Class II Typing, Low/Intermediate-Resolution Technical

CPT-81378-HLA-HIGH-RESOLUTION-MOLECULAR-TYPING-CLASS-I-II-DRB1

CPT 81378: High-Resolution HLA Class I and II Molecular Typing

CPT-81379-HLA-CLASS-I-HIGH-RESOLUTION-TYPING

CPT 81379: High-Resolution HLA Class I Typing

CPT-81380-HLA-HIGH-RESOLUTION-CLASS-I-TYPING

CPT 81380: High-Resolution HLA Class I Molecular Typing

Showing 1–10 of 13

Frequently Asked Questions

References

1.CPT® Codes and Descriptions. AAPC. Retrieved Jul 29, 2026.
2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Jul 29, 2026.
3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Jul 29, 2026.

Published by

Trek Health powers OpenPayer with a leading commercial payer intelligence platform, seamlessly converting fragmented payer data into actionable insights for provider organizations.

Trek Health ingests and normalizes Transparency in Coverage data and payer policy updates to give provider organizations a clear view of how commercial reimbursement behaves across markets, payers, and services. Our platform transforms raw payer disclosures into structured intelligence that supports contract evaluation, payer negotiations, and service line strategy. By combining market benchmarks with ongoing policy visibility, Trek helps teams identify variability, risk, and opportunity in commercial reimbursement. The result is faster insight, stronger negotiating positions, and more informed financial decisions.

Clinical & Coding Specifications

Clinical Context

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when billing only the professional (interpretation) component if separated from the technical lab work.
`TC`	Technical component	Use when billing only the technical component of the lab test (most common for `81377`).
`59`	Distinct procedural service	Use when this HLA test is a separate, distinct service from other procedures on the same date.
`90`	Reference (outside) laboratory	Use when the testing was referred to an outside reference laboratory.
`91`	Repeat clinical diagnostic test	Use when the same test is repeated on the same patient to confirm results within a short timeframe.
`52`	Reduced services	Use when the test is partially reduced or not performed to full protocol and documentation supports reduction.
`53`	Discontinued procedure	Use when testing began but was discontinued for documented reasons (rare for lab assays).
`59`	Distinct procedural service	Use when the HLA assay is distinct from other billed lab services (listed to emphasize distinctness).
`90`	Reference lab	Use when specimen is sent to an external reference lab for performance of `81377`.
`91`	Repeat test	Use when repeat testing is clinically indicated due to prior indeterminate or discordant result.

Taxonomy Code	Specialty	Notes
207RH0000X	Hematopathology	Pathologists who oversee immunogenetics and HLA testing in clinical labs.
207L00000X	Clinical Pathology	Clinical pathologists directing laboratory testing and interpretation.
207K00000X	Molecular Genetic Pathology	Specialists in molecular diagnostics who validate and supervise HLA molecular assays.
208D00000X	Obstetrics & Gynecology	Ordering clinicians for reproductive immunology indications such as recurrent pregnancy loss.
208000000X	Family Medicine	Primary care or reproductive medicine clinicians who may order targeted HLA testing.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`Z31.430`	Encounter for fertility testing; infertility evaluation female	HLA typing may be ordered during fertility workup when immunologic factors are considered in recurrent implantation failure.
`O26.82`	Maternal care for other specified fetal problems; recurrent pregnancy loss	HLA allele group testing can be used in evaluation of immune-mediated causes of recurrent pregnancy loss.
`Z48.01`	Encounter for change or removal of surgical dressings; not directly related	Data not directly applicable to this procedure but included when present in input.
`Z52.2`	Blood donor status	HLA testing can be relevant for donor matching in selected transfusion or transplant contexts.
`D76.1`	Hemophagocytic lymphohistiocytosis	HLA associations may be explored in complex immune dysregulation workups where targeted HLA testing contributes to diagnosis.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`81377`	HLA typing; low or intermediate resolution for one Class II antigen equivalent (allele group)	The primary technical assay performed by the molecular immunogenetics laboratory to determine an HLA Class II allele group.
`81376`	HLA typing; low or intermediate resolution for one Class I antigen equivalent (allele group)	Performed when Class I allele group information is required in addition to Class II; may be ordered concurrently for comprehensive HLA assessment.
`81479`	Unlisted molecular pathology procedure	Used for molecular tests not specifically described by existing CPT codes when additional specialized HLA analyses are required beyond `81377`.
`88360`	Immunohistochemistry or immunocytochemistry, per specimen; initial single antibody stain	Occasionally used when correlated antigen expression studies are performed on tissue in conjunction with HLA testing in complex cases.
`80500`	Tissue typing; serologic testing, HLA-A, -B, -C, -DR, -DQ (each antigen) — historical/alternative methods	Historical or alternate methodology codes that may appear in legacy workflows where serologic typing complements molecular HLA results.

CPT 81370: HLA Class I and II Low/Intermediate-Resolution Molecular Typing

CPT-81371-HLA-A-B-DRB1-LOW-INTERMEDIATE-RESOLUTION-TYPING

CPT 81371: HLA-A, HLA-B, HLA-DRB1 Low/Intermediate Resolution Typing

CPT-81372-HLA-CLASS-I-LOW-INTERMEDIATE-RESOLUTION-TYPING

CPT 81372: HLA Class I Low/Intermediate-Resolution Molecular Typing

CPT-81373-HLA-CLASS-I-LOW-INTERMEDIATE-RESOLUTION

CPT 81373: HLA Class I Low/Intermediate Resolution Molecular Test

CPT-81374-HLA-CLASS-I-LOW-INTERMEDIATE-RESOLUTION

CPT 81374: HLA Class I Low/Intermediate-Resolution Testing

CPT-81375-HLA-CLASS-II-LOW-INTERMEDIATE-RESOLUTION-TYPING

CPT 81375: HLA Class II Low/Intermediate-Resolution Molecular Typing

CPT-81376-HLA-CLASS-II-TYPING-LOW-INTERMEDIATE-RESOLUTION-TECHNICAL

CPT 81376: HLA Class II Typing, Low/Intermediate-Resolution Technical

CPT-81378-HLA-HIGH-RESOLUTION-MOLECULAR-TYPING-CLASS-I-II-DRB1

CPT 81378: High-Resolution HLA Class I and II Molecular Typing

CPT-81379-HLA-CLASS-I-HIGH-RESOLUTION-TYPING

CPT 81379: High-Resolution HLA Class I Typing

CPT-81380-HLA-HIGH-RESOLUTION-CLASS-I-TYPING

CPT 81380: High-Resolution HLA Class I Molecular Typing

Showing 1–10 of 13

Frequently Asked Questions

References

1.CPT® Codes and Descriptions. AAPC. Retrieved Jul 29, 2026.
2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Jul 29, 2026.
3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Jul 29, 2026.

Published by

Trek Health powers OpenPayer with a leading commercial payer intelligence platform, seamlessly converting fragmented payer data into actionable insights for provider organizations.

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CPT 81377: HLA Class II Allele Group Typing, Low/Intermediate Resolution

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Billing Code Overview

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Billing Code Overview

Clinical & Coding Specifications

Clinical Context

Coding Specifications

Related Diagnoses

Related CPT Codes

Related Codes

References

Clinical & Coding Specifications

Clinical Context

Coding Specifications

Related Diagnoses

Related CPT Codes

Related Codes

References

CPT 81377: HLA Class II Allele Group Typing, Low/Intermediate Resolution

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Billing Code Overview

CPT 81377: HLA Class II Allele Group Typing, Low/Intermediate Resolution

Sign up for cpt 81377 policy alerts

Billing Code Overview

Clinical & Coding Specifications

Clinical Context

Coding Specifications

Related Diagnoses

Related CPT Codes

Related Codes

What does CPT 81377 represent and where is it typically performed?

Which billing modifiers are relevant for CPT 81377 and when are they used?

What other CPT codes are commonly associated with or used alongside 81377?

For what clinical scenarios is 81377 commonly ordered according to the page?

Which payers are mentioned and does the page provide specific payer coverage rules for 81377?

References

Clinical & Coding Specifications

Clinical Context

Coding Specifications

Related Diagnoses

Related CPT Codes

Related Codes

What does CPT 81377 represent and where is it typically performed?

Which billing modifiers are relevant for CPT 81377 and when are they used?

What other CPT codes are commonly associated with or used alongside 81377?

For what clinical scenarios is 81377 commonly ordered according to the page?

Which payers are mentioned and does the page provide specific payer coverage rules for 81377?

References