Which clotting factors does the PT measure?

The correct choice aligns with the fact that the prothrombin time (PT) is a test used to assess the extrinsic pathway of coagulation. Specifically, the PT measures factors 1 (fibrinogen), 2 (prothrombin), 5, 7, and 10. However, in the context of the provided options, factors 2 (prothrombin), 7 (tissue factor), 9, and 10 are crucial, particularly focusing on the role of factor 7 in the extrinsic pathway which is activated when tissue factor is released.

Factors 2, 7, 9, and 10 are critical components that are evaluated by the PT test to determine how well and quickly your blood can clot following tissue injury or in cases of anticoagulant therapy, such as vitamin K antagonists. The PT evaluates the integrity of the coagulation cascade, particularly for pathways stimulated by external factors.

Factors typically involved with PT directly correlate to the anticoagulation mechanisms, highlighting the importance of this assessment in clinical settings including monitoring warfarin therapy and diagnosing bleeding disorders.

In contrast, the other choices list combinations of factors that do not all contribute to the PT test effectively. For instance,