Prothrombin time (PT) and INR are ordered on patients who are on regular anticoagulant therapy to ensure the effectiveness of the oral anticoagulant .It is also ordered in patients who show symptoms of bleeding disorders like -
The PT is functional determination of the extrinsic (tissue factor) pathway of coagulation and is extremely sensitive to the vitamin-K dependent clotting factors (factors II, VII, and X). The PT is a widely used laboratory assay for the detection of inherited or acquired coagulation defects related to the extrinsic pathway of coagulation.
INR (International Normalized ratio) is a measure of the patients Prothrombin time expressed as ratio to the standard control.
A prolonged PT means that blood is taking long to clot. INR of 2.5 - 3.5 is advisable to be maintained for a patient on oral anticoagulant.
ordered along with PT to follow the abnormal results.
APTT - determines the functional activity of intrinsic factors of coagulation pathway.
PLATELET COUNT- low platelet count predispose to bleeding.
Fibrinogen test - low fibrinogen level predispose to bleeding.
von Willebrand factor - to rule out von Willebrand disease.
Coagulation factors - factor levels provide in depth analysis of the cause of prolonged PT .