Prothrombin Time (PT) and Partial Thromboplastin Time (PTT)
Fasting Required: No

Specimen: Blood

Results: 2-3 Business Days

Description: The Prothrombin time (PT) test is most often used to check how well anti-coagulant or “blood-thinning” drugs are working. Anti-coagulant drugs help prevent the formation of blood clots. This is particularly important in people who have had a heart attack or other problems with their veins. The drug’s effectiveness can be determined by how much it prolongs the prothrombin-to-thrombin conversion time.

The PTT test is used when someone has unexplained bleeding or clotting. Along with the PT test (which evaluates the extrinsic and common pathways of the coagulation cascade), the PTT is often used as a starting place when investigating the cause of a bleeding or thrombotic episode. It is often used with recurrent miscarriages that often are associated with anticardiolipin and phospholipid antibodies. The PTT and PT tests are also sometimes used as pre-surgical screens for bleeding tendencies, although numerous studies have shown that they are not useful for this purpose. The PTT is also used to monitor heparin anticoagulant therapy as well as other therapeutic anticoagulants such as hirudin or argatroban. These are substitute drugs that may be used when a patient has heparin-induced thrombocytopenia, which is a decreased platelet count.

Methodology: Photo-optical Clot Detection

Limitations: PT/INR: Expected impact by therapeutic levels (potential interference depends upon drug concentration): Warfarin: prolonged; Heparin (UFH or LMWH): little to no effect (reagent contains a heparin neutralizer); Dabigatran or Argatroban (Thrombin Inhibitors): normal to prolonged; Rivaroxaban or Apixaban (Factor Xa Inhibitors): prolonged.

aPTT: Expected impact by therapeutic levels (potential interference depends upon drug concentration): Warfarin: prolonged; Heparin (UFH or LMWH): prolonged; Dabigatran or Argatroban (Thrombin Inhibitors): prolonged; Rivaroxaban or Apixaban (Factor Xa Inhibitors): prolonged.

Alternative Name(s): APTT, PTT, PT

Note: Result turnaround times are an estimate and are not guaranteed. Our reference lab may need additional time due to weather, holidays, confirmation/repeat testing, or equipment maintenance.