LabMed

Increased PT and Increased PTT

Differential Diagnosis

Coumadin therapy in the therapeutic or supratherapeutic range

Moderate to severe vitamin K deficiency

Treatment with high doses of heparin or low molecular weight heparin

Treatment with direct thrombin inhibitors, such as hirudin or related compounds (i.e., lepirudin, refludan) or argatroban

Moderate to severe DIC

Moderate to severe liver disease

A lupus inhibitor with an associated decrease in factor II or a lupus inhibitor strong enough to increase PT, as well as PTT

Suggested Additional Lab Testing

To assess the possibility of DIC, get D-dimer levels.

  • If D-dimers are elevated, measure platelet count and fibrinogen level.

Test for factors II, V, VII, and X to assess a PT prolongation.

Test for factors VIII, IX, XI, and XII to assess a PTT prolongation.

In liver disease, all the factors can be low, except factor VIII, which tends to become elevated because it can be synthesized outside the liver.

  • Obtain liver function tests, especially serum albumin, to determine if the PT and PTT abnormalities could be associated with decreased production of coagulation factors by the liver.

Get a value for PTT after the sample is treated with an enzyme that degrades heparin.

  • If PTT and PT normalize after removal of heparin from the sample, PT and PTT elevations are most likely associated with heparin or low molecular weight heparin treatment.

Do a lupus inhibitor test if there is no explanation for the PT and PTT prolongations from the previously mentioned tests.

  • Factor II level may be useful to accompany the lupus anticoagulant test, because some lupus anticoagulant patients have a low factor II, leading to a prolonged PT.

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