Medical Laboratory Scientist (MLS) ASCP Exam 2025 – 400 Free Practice Questions to Pass the Exam

The test that measures the effectiveness of the extrinsic pathway of coagulation is prothrombin time. This test evaluates the time it takes for blood to clot, specifically assessing factors I, II, V, VII, and X, with a significant focus on factor VII, which is primarily involved in the extrinsic pathway.

In clinical practice, prothrombin time is particularly useful for monitoring patients on anticoagulant therapy such as warfarin since it provides insight into the functioning of the extrinsic pathway. Additionally, it is often reported alongside the International Normalized Ratio (INR), which helps standardize results between different laboratories.

Thrombin time assesses the conversion of fibrinogen to fibrin, activated partial thromboplastin time evaluates the intrinsic and common pathways of coagulation, and reptilase time specifically evaluates fibrinogen and thrombin function without the influence of heparin. Each of these tests assesses different aspects of the coagulation cascade, but prothrombin time is distinct in its evaluation of the extrinsic pathway.