Prothrombin Time (PT), Plasma

Prothrombin is a vitamin K-dependent coagulation protein whose function is inhibited by anticoagulant drugs such as Warfarin which is commonly employed to treat patients who have developed thromboembolic disease and are prone to recurrences or to treat patients for disorders known to be associated with thromboembolic complications. In patients with vitamin K deficiency, acute hepatitis, cirrhosis and primary hepatocellular carcinoma, an abnormal type of prothrombin that lacks clotting activity, does not bind to calcium and does not bind to membrane surfaces is found circulating in plasma.

The Prothrombin Time (PT) is the method of choice for the evaluation of the effects of warfarin on blood coagulation. The dosage of warfarin administered is evaluated by monitoring the PT. In addition to anticoagulant therapy, PT is prolonged in patients with vitamin K deficiency, acute hepatitis, cirrhosis and primary hepatocellular carcinoma. Laboratories report international normalized ratio (INR) in addition to clotting time in seconds. The INR is calculated as PTR/ISI, where PTR is the observed PT ratio (the patient’s PT divided by the mean normal PT in the laboratory) and ISI the international sensitivity index of the thromboplastin reagent used.

2 ml Citrated Plasma Room Temperature

Avoid delay. Avoid clotted, lipemic or haemolysed samples.

Reference range: INR: 0.8-1.1 For patients on medication: “Reference range is case & dose dependent and interpreted clinically”.