Extrinsic system of coagulation is checked by:March 2010

Ans. B: PTBleeding Time (Normal:1-6 min.) is for checking the number of platelets. It is prolonged by lack of platelets. Clotting time (Normal:6-10 min.) varies widely depending upon the method employed, so discarded nowadays. Instead measurements of clotting factors are being done.aPTT/PTT is employed for assessing intrinsic system.Prothrombin time (Normal:12 sec.) gives an good indication of concentration of prothrombin in the blood. Extrinsic pathway is assessed.