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Prothrombin time

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

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