CMS Pharmacogenomic Testing for Warfarin Response: What Billing Teams Need to Know About NCD 333

CMS has modified its National Coverage Determination for pharmacogenomic testing related to warfarin response (NCD 333), with an effective date of March 12, 2026. This policy governs Medicare coverage of CYP2C9 and VKORC1 genetic testing used to predict how individual patients will respond to warfarin anticoagulation therapy. If your practice or health system bills for diagnostic laboratory services in cardiology, hematology, or anticoagulation management, this update warrants immediate attention.

What NCD 333 Covers: CMS Warfarin Pharmacogenomic Testing Policy

Under NCD 333, the Centers for Medicare & Medicaid Services covers pharmacogenomic testing of CYP2C9 or VKORC1 alleles to predict warfarin responsiveness—but only under a Coverage with Evidence Development (CED) framework established under §1862(a)(1)(E) of the Social Security Act. CED coverage means this is not a blanket benefit. Medicare will pay for the test only when specific, documented conditions are met at the time the test is ordered.

The clinical rationale for the policy is grounded in established pharmacogenomics science. Warfarin—most commonly marketed as Coumadin®, which carries an FDA Black Box Warning dating to 2007—is metabolized primarily by the CYP2C9 enzyme, and its anticoagulant activity is affected by genetic variation in both CYP2C9 and VKORC1 genes. Because these genetic variants can predict how a patient will respond to warfarin, testing ideally occurs before the drug is initiated. CMS treats this as a once-in-a-lifetime test, given that a patient's genetic characteristics do not change.

Critically, even when pharmacogenomic testing is covered, it does not replace the need for ongoing PT/INR monitoring—the standard coagulation test. Billing teams should not treat these as interchangeable services.

CMS Coverage Criteria: Three Requirements That Must All Be Met

CMS coverage under NCD 333 is contingent on satisfying all three of the following patient-level criteria simultaneously. Missing any single criterion renders the test non-covered for Medicare billing purposes.

The patient must:

The qualifying clinical study must prospectively examine outcomes in Medicare-aged subjects and address measurable endpoints comparing pharmacogenomic-guided warfarin management to standard management. The required outcome measures include:

If your institution is not currently participating in a CMS-approved CED study for this indication, pharmacogenomic warfarin testing is not a covered Medicare service regardless of clinical rationale or ordering physician documentation.

What Is Not Covered Under CMS NCD 333

Several scenarios fall outside the bounds of NCD 333 coverage, and billing teams should build these into their pre-authorization and charge capture workflows:

• Repeat testing on a patient who has previously had CYP2C9 or VKORC1 allele testing
• Testing ordered after five or more days of warfarin in the current anticoagulation regimen
• Testing performed outside of an approved CED clinical trial — even if the patient is otherwise eligible
• Testing ordered for warfarin management rather than initiation — the policy frames this as a dosing-optimization tool, not a monitoring tool

These are the most common scenarios likely to generate claim denials. Front-end eligibility screening and documentation review prior to test ordering are essential.

Affected Codes

This policy does not list specific CPT or HCPCS codes in its current published form. Billing teams should consult their laboratory partners and the CMS NCD 333 source documentation directly at app.payerpolicy.org/p/cms/333-v1 for the most current code-level guidance, and monitor CMS Local Coverage Determinations (LCDs) from their MAC for any associated code lists.

No ICD-10-CM codes are enumerated in the available policy data at this time.

Prior Authorization and Documentation Requirements

NCD 333 does not outline a formal prior authorization process in the traditional sense—but the CED enrollment requirement functions as a de facto authorization gatekeeping mechanism. The clinical study enrollment must be documented in the patient record, and that documentation should accompany or be accessible at the time of claim submission.

Your billing team should treat CED enrollment verification as a mandatory pre-billing step, equivalent to prior authorization documentation. The absence of verified trial enrollment is grounds for CMS denial, and appeals will be difficult without contemporaneous documentation.

What Your Billing Team Should Do