Prothrombin time
Synonym - Specimen - Reference Value - Method - Description and interpretation
Synonym : Pro-time OR PT
Specimen : Plasma in sodium citrate tube
Reference Valu : 10 to 13 Sec . International normalized ratio ratio (INR) 2.0 to 3.0
Method : Clot detection
DESCRIPTION
Prothrombin time (PT) is a coagulation test performed to measure the time it takes for a firm fibrin clot to form after tissue thromboplastine(factor3) and calcium are added to the sample .It is used to evaluate the extrinsic pathway of the coagulation . Prothrombin is a vitamin K - dependent protein produced by the liver , measurement is reported as time in seconds or percentage of normal activity . PT evaluation is now based on an INR using a standardized thromboplastin reagent to assist in making decisions regarding oral anti coagulation therapy .
In liver disease , the PT reflects the hepatic capacity for protein synthesis . PT responds rapidly to altered hepatic function because the serum half lives of factors 2 and factors 7 are short in ( hours )j
INDICATIONS
1 - Differentiate between deficiencies of clotting factors 2,5,7and 10 which prolonged the PT and congenital coagulation disorders such as hemophilia A ( factor 8 ) and hemophilia B (Factor11 ) which do not alter the PT.
2 - Evaluate the response to anti coagulation therapy
3 - Identify the possible cause of abnormal bleeding , such as epistaxis ,hematoma
4 - Identify individuals who may be prone to bleeding during surgical , obstetric , dental . or invasive diagnostic procedures
5 - Monitor the effects of conditions such as liver disease on hemostasis
6 - Screen for prothrombin deficiency
7 - Screen for vitamin K deficiency
INTERPRETATION
Increased in
1 - Hypofibrinogenemia
2 - Disseminated intravascular coagulation
3 - Hereditary deficiencies of factors 2 ,5 7and 10
4 - Intravascular coagulation
5 - Liver disease , Biliary obstruction
6 - Presence of circulating anti-coagulation
7 - Vitamin K deficiency
8 - Drugs : warfarin