TODAYS PICK (14-07-2010)

Question history: JIPMER,PGI

Prothrombin time detects a defeciency of
a)Factor 7
b)Factor 8
c)Factor 9
d)factor 10


Ans:d

Discussion: reference C.L.Ghai manual of physiology

Prothrombin time:

1. In this test tissue thromboplastin is added to oxalated or citrated plasma and the mixture is incubated at 37 degree C. Calcium chloride sol. is then added to it and the the stop watch is started to calculate the time of formation of fibrin clot.
2. Normal prothrombin time is 11-16 seconds.
3. Since no platelets are involved in this test it doesnot test intrinsic system . It tests only extrinsic system of coagulation.
4. Along with Prothrombin activity this test also is sensitive for defeciency of Factors I,V,VII and X.
5. Prothrombin time is also prolonged in oral anticoagulants,liver failure and defeciency of vitamin.K.
6. Use: this test is used as a monitor the patients receiving waarfarin therapy.Blood from a normal person is taken as a control and the result is expressed as ratio(PTR).
7. Normal PTR is 0.9-1.2.

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