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

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

CMS PTT coverage policy under NCD 74 in the Medicare system draws a clear line between medically justified testing and routine ordering—and it has real claim denial consequences. The policy does not list specific CPT codes within the NCD itself, but PTT billing typically runs through the lab fee schedule and is subject to medical necessity documentation requirements that this update reinforces. If your lab or physician practice bills PTT tests for Medicare patients, read this before March 7, 2026.

Quick-Reference Table

CMS PTT Coverage Criteria and Medical Necessity Requirements 2026

This is where NCD 74 gets specific, and where your billing team can't afford to be vague.

The Centers for Medicare & Medicaid Services cover the PTT test under four defined clinical scenarios. Each one requires documentation that ties the test to a specific patient condition or clinical need. Generic protocols and standing orders don't cut it—and that's not an interpretation, it's written directly into the policy.

Indication 1: Monitoring unfractionated heparin therapy. This is the most common covered use. The PTT is the standard way to quantify and regulate heparin dosing. Here's the wrinkle: if a patient is on heparin and warfarin simultaneously during a transition, you may need both PTT and PT (Prothrombin Time). But the policy is explicit—outside of that transition, ordering both is not automatically justified. PT and PTT must be justified separately. Document why each test was ordered. If your billing team sees dual ordering without transition documentation, flag it before the claim goes out.

Indication 2: Signs or symptoms of hemorrhage or thrombosis. CMS covers PTT when a patient shows clinical signs pointing to a bleeding or clotting problem. The policy gives concrete examples: abnormal bleeding, hematoma, petechiae suggesting thrombocytopenia or disseminated intravascular coagulation (DIC), or a swollen extremity with or without trauma. The note on DIC matters—PTT is one of the key tests in that workup. Make sure your documentation reflects the presenting signs, not just the diagnosis.

Indication 3: Known history of hemorrhage or thrombosis risk. This is the broadest covered indication, and it covers a long list of conditions. Hemophilia, von Willebrand's disease, liver disease and failure, lupus erythematosus, Factor VIII inhibitor, lupus-like anticoagulant, DIC, arterial and venous thrombosis, hypercoagulable states, sepsis, nephrosis, renal failure, dysfibrinogenemia, and afibrinogenemia are all explicitly listed. If your patient has one of these conditions documented in their record and the PTT is part of ongoing management, that's covered. The diagnosis code in the claim needs to match.

Indication 4: Pre-procedure risk assessment. PTT is covered before invasive procedures or surgery—but only under specific conditions. The patient must have a personal or family history of bleeding, or they must already be on heparin therapy. A hospital or clinic protocol requiring PTT on every surgical patient is not, by itself, a sufficient reason for Medicare to pay. The policy language is direct: "Hospital/clinic-specific policies, protocols, etc., in and of themselves, cannot alone justify coverage." If your surgeons or anesthesiologists order PTT as a blanket pre-op screen, that's your highest-risk ordering pattern under this coverage policy. Fix the documentation workflow before March 7, 2026.

CMS PTT Exclusions and Non-Covered Indications

The policy's limitations section is where most PTT billing problems originate.

Warfarin monitoring. PTT does not measure warfarin's effect on coagulation in a useful way. PT and INR are the right tests for that. CMS will not cover routine PTT orders for patients on warfarin alone. There are two narrow exceptions: when heparin is being discontinued and the patient is transitioning to warfarin, and when the PT is markedly prolonged due to warfarin toxicity. Outside of those two scenarios, a PTT order on a warfarin-only patient is a denial waiting to happen.

Repeat testing without clinical change. CMS doesn't cover repeat PTT orders simply because time has passed. The need to repeat must be driven by a change in the patient's medical condition or a change in heparin dosing. If your hospitalists are ordering daily PTT as routine monitoring without documented dosing adjustments or clinical changes, that pattern will not survive a medical necessity review.

Pre-procedure testing without patient-specific history. As noted above, institutional policy is not a covered reason. This one catches a lot of hospitals off guard, especially in high-volume surgical programs where standing orders are common.

Coverage Indications at a Glance

CMS PTT Billing Guidelines and Action Items 2026

PTT billing under NCD 74 is a volume game—low dollar per test, but high denial risk across large orders. Here's how to get ahead of it.

If your practice sees high volumes of anticoagulation management or runs a busy pre-op lab program, loop in your compliance officer before March 7, 2026. The pre-procedure limitation is the policy's sharpest edge, and it's easy to miss at scale.

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

Specific Codes Listed in NCD 74

The NCD 74 policy document does not list specific CPT or HCPCS codes within the policy text itself. CMS notes that applicable codes appear in the quarterly Covered Code Lists linked from the policy page. Check the current Covered Code Lists at the CMS source to confirm which codes are covered under this NCD for the current quarter.

What This Means for PTT Billing

Do not assume that because NCD 74 covers PTT conceptually, every code your lab uses is automatically covered. The quarterly Covered Code Lists govern which specific codes are reimbursable under this NCD in a given period. Verify your codes against the current list before billing. If a code falls off the list between quarters, claims will deny—and you won't know why unless someone is checking.

This also connects to local coverage determination (LCD) policy. Your Medicare Administrative Contractor (MAC) may have supplemental coverage policies that interact with NCD 74. Check with your MAC for any regional guidance that applies to PTT billing in your jurisdiction. MAC-level LCDs can be more restrictive than the national policy and can add documentation requirements that NCD 74 alone doesn't specify.