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National Coverage Determination (NCD) for Partial ThromboplastinTime (PTT) (190.16)

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Benefit Category
Diagnostic Laboratory Tests

Note: This may not be an exhaustive list of all applicable Medicare benefit categories for this item or service.

Item/Service Description

Basic plasma coagulation function is readily assessed with a few simple laboratory tests: the PTT, prothrombin time (PT), thrombin time (TT), or a quantitative fibrinogen determination. The PTT test is an in vitro laboratory test used to assess the intrinsic coagulation pathway and monitor heparin therapy.

Indications and Limitations of Coverage


  1. The PTT is most commonly used to quantitate the effect of therapeutic unfractionated heparin and to regulate its dosing. Except during transitions between heparin and warfarin therapy, in general both the PTT and PT are not necessary together to assess the effect of anticoagulation therapy. PT and PTT must be justified separately.
  2. A PTT may be used to assess patients with signs or symptoms of hemorrhage or thrombosis. For example: abnormal bleeding, hemorrhage or hematoma petechiae or other signs of thrombocytopenia that could be due to disseminated intravascular coagulation; swollen extremity with or without prior trauma.
  3. A PTT may be useful in evaluating patients who have a history of a condition known to be associated with the risk of hemorrhage or thrombosis that is related to the intrinsic coagulation pathway.  Such abnormalities may be genetic or acquired. For example: dysfibrinogenemia; afibrinogenemia (complete); acute or chronic liver dysfunction or failure, including Wilson's disease; hemophilia; liver disease and failure; infectious processes; bleeding disorders; disseminated intravascular coagulation; lupus erythematosus or other conditions associated with circulating inhibitors, e.g., Factor VIII Inhibitor, lupus-like anticoagulant, etc.; sepsis; von Willebrand's disease; arterial and venous thrombosis, including the evaluation of hypercoagulable states; clinical conditions associated with nephrosis or renal failure; other acquired and congenital coagulopathies as well as thrombotic states.
  4. A PTT may be used to assess the risk of thrombosis or hemorrhage in patients who are going to have a medical intervention known to be associated with increased risk of bleeding or thrombosis. An example is as follows: evaluation prior to invasive procedures or operations of patients with personal or family history of bleeding or who are on heparin therapy.


  1. The PTT is not useful in monitoring the effects of warfarin on a patient's coagulation routinely. However, a PTT may be ordered on a patient being treated with warfarin as heparin therapy is being discontinued. A PTT may also be indicated when the PT is markedly prolonged due to warfarin toxicity.
  2. The need to repeat this test is determined by changes in the underlying medical condition and/or the dosing of heparin.
  3. Testing prior to any medical intervention associated with a risk of bleeding and thrombosis (other than thrombolytic therapy) will generally be considered medically necessary only where there are signs or symptoms of a bleeding or thrombotic abnormality or a personal history of bleeding, thrombosis or a condition associated with a coagulopathy. Hospital/clinic-specific policies, protocols, etc., in and of themselves, cannot alone justify coverage.

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Cross Reference

Also see the Medicare Claims Processing Manual, Chapter 120, Clinical Laboratory Services Based on Negotiated Rulemaking.

Transmittal Number


Revision History

07/2002 - Implemented NCD. Effective date 11/25/02. Implementation date 1/01/03. (TN AB-02-110) (CR 2130)

07/2004 - Published NCD in the NCD Manual without change to narrative contained in PM AB-02-110. Coding guidance now published in Medicare Lab NCD Manual. Effective and Implementation dates NA. (TN 17) (CR 2130)