RetiredCapital BluecrossPolicy AHS - G2107

Measurement of Thromboxane Metabolites for ASA Resistance

This policy governs coverage determination for tests that measure thromboxane metabolites (e.g., urinary 11‑dehydrothromboxane B2 / AspirinWorks) to evaluate aspirin resistance for Capital BlueCross members.

Policy Summary

PayerCapital Bluecross

PolicyMeasurement of Thromboxane Metabolites for ASA Resistance

Policy CodePolicy AHS - G2107

Change TypeRetired

Effective Date03/01/2025

Next Review DateN/A

Key ActionDo not submit claims for urinary thromboxane metabolite testing to evaluate aspirin resistance; requests will be denied as the test does not meet coverage criteria.

SourceLink

POLICY UPDATE CHANGES

Policy was retired as of 03/01/2025.

Not coveredcoverage stance

≤1500 pgFDA cutoff

15–25%estimated prevalence

82570,84431procedure codes

2FDA-cleared tests

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~20+evidence citations

Coverage Determination

Not medically necessary — urinary thromboxane metabolite testing

Not covered for all indications.

Primary stance: Measurement of thromboxane metabolites in urine (e.g., AspirinWorks) to evaluate aspirin resistance does not meet coverage criteria for any indication.

Lack of available published scientific literature confirming that the test is required and beneficial for diagnosis and treatment.

Measurement of thromboxane metabolites in urine to evaluate aspirin resistance is excluded from coverage for all indications. The policy states that these tests "DOES NOT MEET COVERAGE CRITERIA" because there is a lack of available published scientific literature confirming the tests are required and beneficial for diagnosis or treatment.

Some assays for aspirin effect are marketed with FDA 510(k) clearance (for example, VerifyNow-Aspirin and AspirinWorks). However, many laboratories instead use laboratory-developed tests (LDTs) that are validated and performed in-house. LDTs are not approved or cleared by the U.S. Food and Drug Administration and are regulated by CMS under CLIA '88 as high-complexity tests; FDA clearance is not required for clinical use.

Urinary thromboxane metabolite testing (for example, AspirinWorks) to evaluate aspirin resistance is considered not medically necessary and does not meet coverage criteria for any indication.

Procedure Codes and Clinical Thresholds

Procedure codes referencedCPT

82570	Creatinine; other source.
84431	Thromboxane metabolite(s), including thromboxane if performed, urine

Applicable CPT/HCPCS Procedure CodesCPT

82570	Creatinine; other source.
84431	Thromboxane metabolite(s), including thromboxane if performed, urine

inv-07: FDA aspirin effect cutoff (urinary 11dhTxB2)

FDA-established cutoff for aspirin effect≤1500 pg 11dhTxB2 per mg creatinine

Observed non‑aspirin users above cutoff88.2% (180/204) of samples from individuals not taking aspirin were above the cutoff

Proportion of aspirin users indicating lack of aspirin effect5.5% (11/201) of aspirin users exceeded the cutoff across doses studied

Provider Responsibilities and Billing Notes

Denial Risk

Prior Authorization / Denial Notice

Prior authorization is NOT available for measurement of urinary thromboxane metabolites (e.g., AspirinWorks). Requests for this test will be denied because the test is considered not medically necessary for all indications.

Affected procedure codes for authorization and claims submission: 82570, 84431

Billing Rule

Coding to Reference for Authorization

When submitting prior authorization requests or claims, reference the procedure codes listed in this policy (82570, 84431). Omitting these codes or using alternate codes may cause claim processing issues or administrative delays.

Reference CPT codes: 82570; 84431

Clinical Background

Aspirin exerts its antiplatelet effect by irreversibly inhibiting cyclooxygenase-1 (COX-1), which reduces production of thromboxane A2 (TXA2) and thereby decreases platelet activation and aggregation. The concept of "aspirin resistance" refers to situations in which aspirin fails to reduce TXA2-mediated platelet activation. Urinary 11‑dehydro‑thromboxane B2 (11dhTxB2) has been proposed as a systemic marker of TXA2 generation and is measured by commercial assays (for example, AspirinWorks). Despite this biological rationale, the policy concludes that measurement of urinary thromboxane metabolites to assess aspirin resistance lacks sufficient published evidence of clinical benefit and therefore does not meet coverage criteria.

Key Terms and Test Descriptions

inv-17: Aspirin resistance — definition

DefinitionInability of aspirin to decrease platelet production of thromboxane A2, leading to continued platelet activation and aggregation

Clinical contextProposed mechanism: failure of aspirin to inhibit COX‑1–mediated TXA2 production

ImplicationMay be evaluated by platelet function tests or thromboxane metabolite measurements, but assays vary in prevalence estimates

inv-18: 11‑dehydro‑thromboxane B2 (11dhTxB2) — definition

Analyte11‑dehydro‑thromboxane B2 (11dhTxB2), a urinary metabolite of thromboxane A2 (TXA2)

Proposed useMarker proposed to indicate systemic TXA2 generation and aspirin effect

Policy Summary

PayerCapital Bluecross

PolicyMeasurement of Thromboxane Metabolites for ASA Resistance

Policy CodePolicy AHS - G2107

Change TypeRetired

Effective Date03/01/2025

Next Review DateN/A

Key ActionDo not submit claims for urinary thromboxane metabolite testing to evaluate aspirin resistance; requests will be denied as the test does not meet coverage criteria.

SourceLink

On This Page

Note

Government Policy Precedence

If there is a conflict between this policy and any applicable government (Medicare/Medicaid) policy — for example Local Coverage Determinations (LCDs) or National Coverage Determinations (NCDs) — the government policy takes precedence. Providers should follow the most current Medicare and state Medicaid guidance when it differs from this policy.

Documentation Required

Required Documentation Details

Documentation submitted with requests or claims should explicitly state which assay was performed (for example: VerifyNow-Aspirin, AspirinWorks, or a specific laboratory-developed test [LDT]). Include supporting laboratory reports and method details as available to facilitate review.

Specify assay name (VerifyNow-Aspirin, AspirinWorks, or LDT)
Include lab report and method details when available

Prior Authorization

Provider Operational Impact

Providers should be aware that measurement of thromboxane metabolites in urine (e.g., AspirinWorks) does not meet coverage criteria and will be denied. Operationally, denials may affect authorization workflows and payment. Contact provider services for questions about claim status or appeals.

LimitationUrinary 11dhTxB2 is not specific to platelets; up to ~30% or more may derive from extra‑platelet sources (monocytes, macrophages, plaque, other tissues)

inv-19: VerifyNow-Aspirin Assay — definition and intended use (510(k)-cleared)

TestVerifyNow‑Aspirin Assay

Regulatory statusFDA 510(k) marketing clearance (October 2004)

Intended useQualitative assay to aid detection of platelet dysfunction due to aspirin ingestion in citrated whole blood for point‑of‑care or laboratory use

inv-20: AspirinWorks — definition and intended use (510(k)-cleared)

TestAspirinWorks (AspirinWorks Test Kit)

Regulatory statusFDA 510(k) marketing clearance (May 2007)

Intended useEnzyme‑linked immunoassay to measure urinary 11dhTxB2 to aid qualitative detection of aspirin effect in apparently healthy individuals post ingestion

inv-21: Laboratory-developed tests (LDTs) — definition and regulatory note (CLIA)

DefinitionLaboratory‑developed tests (LDTs) are assays developed and validated in‑house by clinical laboratories

Regulatory noteLDTs are regulated by CMS under CLIA '88 as high‑complexity tests and are not approved or cleared by the FDA

Clinical useFDA clearance or approval is not currently required for clinical use of LDTs, but labs must validate and perform them in‑house