Partial Thromboplastin Time (PTT) — NCD 74 | CMS Coverage Update

TL;DR: The Centers for Medicare & Medicaid Services modified NCD 74, its Partial Thromboplastin Time (PTT) coverage policy, effective March 7, 2026. Here's what billing teams need to know before submitting claims.

CMS PTT coverage policy under NCD 74 in the Medicare system draws clear lines around when a PTT test is — and isn't — medically necessary. This policy governs diagnostic laboratory claims for PTT testing, which assesses the intrinsic coagulation pathway and monitors unfractionated heparin therapy. No specific CPT codes are listed in the current policy document, but the indications and limitations carry real financial exposure if your team isn't documenting to the right standard.

Quick-Reference Table

CMS Partial Thromboplastin Time Coverage Criteria and Medical Necessity Requirements 2026

NCD 74 is the National Coverage Determination governing Medicare coverage of PTT testing under the Diagnostic Laboratory Tests benefit category. The policy is specific about when PTT clears the medical necessity bar — and when it doesn't.

CMS recognizes four main indications for covered PTT testing.

Monitoring unfractionated heparin therapy. This is the most common covered use. PTT quantifies the effect of unfractionated heparin and guides dosing. If your patient is on heparin, a PTT claim is on solid ground.

Signs or symptoms of hemorrhage or thrombosis. The policy lists examples: abnormal bleeding, hemorrhage, hematoma, petechiae, signs of thrombocytopenia possibly linked to disseminated intravascular coagulation (DIC), or a swollen extremity with or without trauma. Documentation must connect the test to the presenting symptom. Don't assume the diagnosis code carries the claim — the note needs to support it.

History of a condition associated with hemorrhage or thrombosis risk involving the intrinsic coagulation pathway. CMS lists a long set of qualifying conditions: dysfibrinogenemia, afibrinogenemia, acute or chronic liver dysfunction or failure (including Wilson's disease), hemophilia, liver disease and failure, infectious processes, bleeding disorders, DIC, lupus erythematosus, other conditions involving circulating inhibitors (Factor VIII Inhibitor, lupus-like anticoagulant), sepsis, von Willebrand's disease, arterial and venous thrombosis, hypercoagulable states, nephrosis or renal failure, and other acquired or congenital coagulopathies. This is a wide list. The key is that the condition must be linked to the intrinsic coagulation pathway — and that link needs to be in the documentation.

Pre-procedure risk assessment. A PTT is covered before a medical intervention associated with bleeding or thrombosis risk — but only when the patient has signs or symptoms of a bleeding or thrombotic abnormality, a personal history of bleeding or thrombosis, or is currently on heparin therapy. Hospital-wide protocols or standing orders don't satisfy this requirement on their own.

That last point is where a lot of claims fall apart. CMS is explicit: facility-specific protocols, by themselves, cannot justify coverage. If your institution has a blanket pre-op PTT order, those claims need individual documentation to survive audit.

Whether PTT testing is covered under Medicare depends entirely on the documentation in the medical record — not the test order alone. This coverage policy doesn't allow prior authorization as a standalone workaround. Every claim needs its own documented rationale.

CMS Partial Thromboplastin Time Exclusions and Non-Covered Indications

This is where the policy gets specific — and where claim denial risk is highest.

PTT for routine warfarin monitoring is not covered. CMS is clear: PTT does not usefully monitor the anticoagulant effect of warfarin. Ordering PTT for a patient on warfarin, without a separate clinical reason, doesn't meet medical necessity.

There are two narrow exceptions. First, PTT may be covered during the transition from heparin to warfarin — specifically as heparin is being discontinued. Second, PTT may be covered when the PT is markedly prolonged due to warfarin toxicity. Outside of those scenarios, routine PTT-plus-PT pairing on warfarin patients is a red flag.

PTT and PT ordered together without separate justification. CMS states that, except during heparin-to-warfarin transitions, ordering both PTT and PT to assess anticoagulation therapy is generally not necessary. Each test must be justified separately. If your team routinely orders both as a panel, audit those claims. You need individual clinical rationale documented for each test.

Pre-op PTT without clinical indication. As noted above, pre-operative PTT based solely on a facility protocol doesn't qualify. The patient must have signs, symptoms, or a personal history of a bleeding or thrombotic condition — or must be on heparin therapy.

Repeat testing without documented change. The need to repeat PTT is driven by changes in the patient's underlying medical condition or heparin dosing. Serial PTT orders on a stable patient, without documented changes, are vulnerable. Make sure your notes reflect what changed and why the repeat test was ordered.

Coverage Indications at a Glance

CMS Partial Thromboplastin Time Billing Guidelines and Action Items 2026

The real issue with NCD 74 isn't complexity — the policy is readable. The issue is documentation discipline. Here's what to do before March 7, 2026.

CPT, HCPCS, and ICD-10 Codes for Partial Thromboplastin Time Under NCD 74

The current NCD 74 policy document does not list specific CPT, HCPCS, or ICD-10 codes. CMS notes that applicable codes are published in quarterly Covered Code Lists — refer to those lists directly on the CMS website for the current code-level detail.

This is a real gap if you're trying to build or validate your charge capture. Don't assume your existing PTT code mapping is correct without cross-referencing the current quarterly Covered Code List. CMS also directs billers to Chapter 120 of the Medicare Claims Processing Manual, Clinical Laboratory Services Based on Negotiated Rulemaking, for claims processing instructions.

For PTT billing, work with your laboratory billing team to confirm the specific CPT codes in your charge master, then validate each against the indications in NCD 74. If the quarterly list shows a code with coverage restrictions, your documentation requirements need to match.

The absence of codes in the policy body itself isn't a free pass. CMS can and does deny PTT claims when the documentation doesn't match the indication criteria — regardless of whether the code itself appears on a covered list.