MRCP UK EXAMINATIONS

Detailed explanation-1: -Factor VIIa goes on to activate factor X into factor Xa. This is the point where both extrinsic and intrinsic pathways become one. The extrinsic pathway is clinically measured as the prothrombin time (PT).

Detailed explanation-2: -The PT evaluates the extrinsic and common pathways, specifically factors VII, X, V, II and fibrinogen. Because of the short half-life of factor VII, the PT is sensitive to vitamin K deficiency or antagonism. The APTT evaluates the intrinsic and common pathways; only factors VII and XIII are not evaluated.

Detailed explanation-3: -A basic understanding of the coagulation pathway is required to interpret prothrombin time (PT) result (see the image below). The prothrombin time is a measure of the integrity of the extrinsic and final common pathways of the coagulation cascade.

Detailed explanation-4: -Prothrombin time requires the presence of factors I, II, V, VII, and X. It measures the extrinsic pathway of coagulation and can be used in conjunction with the activated partial thromboplastin time (aPTT) which measures the intrinsic pathway.

Detailed explanation-5: -PT/INR use is typically in conjunction with activated partial thromboplastin time (aPTT), which evaluates the intrinsic and common pathways of coagulation.