CurrentUnitedHealthcarePolicy 2025R0111B

DEX Z-Code® submission for Molecular Diagnostic Tests (MDT)

Governs submission and billing requirements for molecular pathology and molecular diagnostic tests (MDT) billed on CMS-1500 and UB04 forms for UnitedHealthcare Commercial and Individual Exchange products; affects all providers submitting these claims.

Policy Summary

PayerUnitedHealthcare

PolicyDEX Z-Code® submission for Molecular Diagnostic Tests (MDT)

Policy CodePolicy 2025R0111B

Change TypeTemplate transfer and Q&A updates

Effective Date

Next Review Date

Key ActionSubmit the appropriate DEX Z-Code® adjacent to the molecular pathology CPT code in the specified claim field and report 1 unit of service.

SourceLink

POLICY UPDATE CHANGES

Question and Answers Section (#8) added.

Transferred content to shared policy template and updated Application section to indicate this policy applies to all UnitedHealthcare Commercial and Individual Exchange benefit plans.

Question and Answers Section (#2) updated.

1unit of service required when reporting an MDT

DEX Z-Code®unique identifier required

CMS1500/UB04claim forms

Deniedduplicate CPTs

MDT Submission and Coverage Criteria

Policy Summary

PayerUnitedHealthcare

PolicyDEX Z-Code® submission for Molecular Diagnostic Tests (MDT)

Policy CodePolicy 2025R0111B

Change TypeTemplate transfer and Q&A updates

Effective Date

Next Review Date

Key ActionSubmit the appropriate DEX Z-Code® adjacent to the molecular pathology CPT code in the specified claim field and report 1 unit of service.

SourceLink

On This Page

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.

MDT submission and coding criteria

Claims for molecular pathology and molecular diagnostic tests (MDT) are considered for reimbursement only when submitted with the appropriate CPT/HCPCS code(s) and the corresponding DEX Z-Code® placed in the required claim field; additional rules apply for units, single‑specimen reporting, and duplicate code reporting.

ALL of the following

ALL of the following
- DEX Z-Code® must be submitted adjacent to the molecular pathology CPT/HCPCS code in the specified claim comment/narrative field (professional or facility).
  Professional claim fields: Loop 2400 or SV-101-7 for 837P; Box 19 for paper professional claims. Facility claim fields: Line SV-202-7 for 837I; Block 80 for UB04.
ALL of the following
- Report the CPT and/or HCPCS code(s) that most accurately describe the specific test performed as assigned through the Palmetto DEX Z-Code® registry.
ALL of the following
- Enter 1 unit of service when reporting an MDT.1 UOS
ALL of the following
- Testing on a single specimen that yields a single result should be reported with a single CPT code that includes all methodologies, genes, analytes and components; do not use modifiers to report multiple codes for a single specimen.
ALL of the following
- Do not submit duplicate or multiple molecular pathology CPT codes reported with the same DEX Z-Code® for the same patient on the same date of service; UnitedHealthcare will deny such duplicates.

Alternate/Related guidance: When no other specific molecular pathology code is applicable, unlisted/misc molecular pathology coding guidance applies (see coding section).

Code Guidance and Units

Unlisted/NOC guidanceCPTCovered

81479

Unlisted/misc molecular pathology code when no other code is applicable

Units per single-procedure specimen

Units per single-procedure specimenPer CMS National Correct Coding policy, when a single procedure is performed on a single specimen, only one unit of service may be reported.

Multiple specimens same dateIf separate specimens are tested on the same date for distinctly separate indications, report the initial specimen without a modifier and report the additional specimen with an appropriate modifier supported by documentation.

Modifiers not for multiple codes on one specimenModifiers should not be used to report multiple codes when a single specimen is tested; the single reported code must include all methodologies, genes, analytes and components.

Claim Submission and Billing Actions

Documentation Required

Claim submission placement and units

Select the appropriate molecular pathology CPT code, enter 1 unit of service, and place the DEX Z-Code® identifier adjacent to the CPT code in the required claim comment/narrative field: Loop 2400/SV-101-7 for 837P (electronic), Box 19 for paper professional claims, Line SV-202-7 for 837I (institutional) electronic claims, or Block 80 for UB04 facility claims.

Select appropriate Molecular Pathology CPT code
Enter 1 unit of service (UOS)
Place DEX Z-Code® adjacent to CPT in the comment/narrative field: Loop 2400/SV-101-7 (837P), Box 19 (paper professional), Line SV-202-7 (837I), or Block 80 (UB04)

Denial Risk

Duplicate/multiple CPT reporting rule

Do not submit duplicate or multiple molecular pathology CPT codes with the same DEX Z-Code® for the same patient on the same date of service; UnitedHealthcare will deny such duplicate/multiple CPT submissions.

Submit one CPT code and one DEX Z-Code® when multiple genes produce a single result
Duplicates (same CPTs with the same DEX Z-Code® on the same date of service for the same patient) will be denied

Key Definitions

Molecular Pathology

DefinitionMolecular Pathology procedures are laboratory analyses of nucleic acid (DNA, RNA) to detect gene variants indicative of germline or somatic conditions, or to test for histocompatibility antigens (e.g., HLA).

Reporting requirementSubmit one CPT code and a DEX Z-Code® for tests that may involve multiple genes producing a single result; duplicate or multiple molecular pathology CPT codes with the same DEX Z-Code® for the same patient/date will be denied.

CPT seriesMolecular Pathology Codes are described in the CPT 80000 series.

DEX Z-Code® Identifiers

What it isA unique 5-character alpha-numeric code assigned within the DEX® Diagnostics Exchange (administered by Palmetto GBA) to identify specific molecular diagnostic tests.

Placement requirementDEX Z-Code® must be submitted in the first position of the required claim comment/narrative field (Loop 2400/SC-101-7 or Box 19 for professional; Line SV-202-7 or Box 80 for facility claims).

PurposeUsed with molecular pathology CPT codes to identify the exact test performed and facilitate reimbursement processing.

Molecular Diagnostic Test (MDT)

DefinitionA Molecular Diagnostic Test (MDT) is a test involving detection or identification of nucleic acids (DNA/RNA), proteins, chromosomes, enzymes, chemotherapy sensitivity and/or other metabolites; may include multiple components.

Reporting formatReport the appropriate molecular pathology CPT/HCPCS code together with the corresponding DEX Z-Code® in the required claim field to be considered for reimbursement.

Single-specimen ruleTesting on a single specimen should be reported with a single code that includes all methodologies, genes, analytes and components; do not use modifiers to report multiple codes for a single specimen.