Prothrombin Time (PT) — NCD 80 | CMS Coverage Update

TL;DR: The Centers for Medicare & Medicaid Services modified NCD 80, the national coverage determination governing prothrombin time (PT) testing, effective March 7, 2026. Here's what billing teams need to know.

CMS prothrombin time coverage policy under NCD 80 affects any provider billing PT or PT/INR tests to Medicare patients — including anticoagulation clinics, hospital outpatient labs, and physician office labs. The policy does not list specific CPT codes in this version, but the coverage criteria are detailed and frequency-based limitations carry real claim denial risk if your documentation doesn't align. This update is worth a close read before your next billing cycle.

Quick-Reference Table

CMS Prothrombin Time Coverage Criteria and Medical Necessity Requirements 2026

NCD 80 covers PT testing under Medicare's diagnostic laboratory benefit category. The coverage policy is structured around four distinct clinical indications. Each one carries its own medical necessity requirements. Meet one of them, and the test is covered. Miss all four, and you're looking at a denial.

Indication 1: Warfarin monitoring. CMS covers PT to assess patients taking warfarin. The policy is explicit that PT is generally not useful for monitoring patients on heparin alone — if the patient isn't also on warfarin, this indication doesn't apply.

Indication 2: Signs or symptoms of abnormal bleeding or thrombosis. This is broader. CMS covers PT for patients presenting with swollen extremities with or without prior trauma, unexplained bruising, abnormal bleeding, hemorrhage, hematoma, petechiae, or other signs of thrombocytopenia that could be related to disseminated intravascular coagulation (DIC). Document the specific sign or symptom. "Abnormal bleeding" as a freestanding note won't carry a claim through audit.

Indication 3: Known conditions associated with bleeding or thrombosis risk. This is the longest list in the policy and covers a wide range of genetic and acquired conditions tied to the extrinsic coagulation pathway. Covered conditions include dysfibrinogenemia, afibrinogenemia, acute or chronic liver dysfunction or failure (including Wilson's disease and hemochromatosis), DIC, congenital and acquired deficiencies of factors II, V, VII, and X, vitamin K deficiency, lupus erythematosus, hypercoagulable state, paraproteinemia, lymphoma, amyloidosis, acute and chronic leukemias, plasma cell dyscrasia, HIV infection, malignant neoplasms, hemorrhagic fever, salicylate poisoning, obstructive jaundice, intestinal fistula, malabsorption syndrome, colitis, chronic diarrhea, peripheral venous or arterial thrombosis, pulmonary emboli, myocardial infarction, organ transplantation, and circulating coagulation inhibitors. That's a long list — and CMS means it to be. The key is that the condition must be related to the extrinsic coagulation pathway. Document the connection.

Indication 4: Pre-procedure hemorrhage or thrombosis risk assessment. PT is covered when a patient is about to undergo a medical intervention with known bleeding or thrombosis risk. This applies specifically to patients with a personal history of bleeding or a condition associated with coagulopathy, and to patients before thrombolytic medication. "Pre-op labs ordered" is not sufficient documentation. The note needs to reflect the patient's history and the specific procedural risk.

One important nuance: CMS states that the indications above apply whether or not the patient is also self-testing PT at home. Self-monitoring does not change the reimbursement rules or the medical necessity criteria. Your billing guidelines should not treat home self-testers differently when documenting inpatient or outpatient PT claims.

Prior authorization is not listed as a requirement under NCD 80. However, that doesn't eliminate documentation exposure. CMS policies without prior authorization requirements still carry post-payment audit risk, and frequency limitations here are specific enough to trigger scrutiny.

CMS Prothrombin Time Exclusions and Non-Covered Indications

The policy doesn't designate PT testing as experimental or investigational. But it does set hard frequency limitations that function as practical coverage limits.

For stable warfarin patients, CMS states it is "ordinarily not necessary" to repeat the PT test more frequently than the clinical picture warrants. That's intentionally vague, but it signals that repeat testing without documented clinical change will face scrutiny. If your anticoagulation clinic runs weekly PT/INR on every stable patient, you need documentation to support each test.

For ESRD patients, the rule is more specific: testing more than once per week requires documentation of medical necessity beyond chronic renal failure or renal failure unspecified. Chronic kidney disease alone — without a documented acute change or additional coagulopathy — won't justify more-than-weekly PT billing for ESRD patients. This is one of the sharper edges in this policy. Make sure your nephrology and ESRD billing teams know this limitation.

Heparin-only patients are also explicitly excluded from the warfarin monitoring indication. If your team is billing PT for patients on anticoagulation without checking whether warfarin is in the picture, clean that up now.

Coverage Indications at a Glance

CMS Prothrombin Time Billing Guidelines and Action Items 2026

If you're running a high volume of PT tests across multiple indications and you're not sure how this modified policy applies to your payer mix, talk to your compliance officer before March 7, 2026.

CPT, HCPCS, and ICD-10 Codes for Prothrombin Time Under NCD 80

The policy data for NCD 80 in this version does not include a specific list of CPT, HCPCS, or ICD-10 codes. CMS did not publish a code table alongside this coverage policy update.

That's not unusual for NCD-level policies — the national determination sets coverage criteria, and code-level specificity is often left to the Medicare fee schedule and MAC-level guidance. For PT billing, your team should confirm the correct CPT codes directly with your MAC and verify alignment with the current Medicare Clinical Laboratory Fee Schedule.

When CMS does not publish codes in the NCD itself, your claim denial exposure shifts entirely to documentation. The criteria above are your only guide to what CMS will and won't pay. That makes documentation discipline even more important for prothrombin time billing under this policy.