What is the difference between PT and PTT tests?

The Prothrombin Time (PT) and Partial Thromboplastin Time (PTT) tests are both used to assess blood clotting but focus on different aspects of the clotting process. PT primarily measures the function of factors in the extrinsic and common clotting pathways, including factors I, II, V, VII, and X. PTT, on the other hand, evaluates factors in the intrinsic and common clotting pathways, including factors VIII, IX, XI, and XII. These tests help diagnose different clotting disorders, so your healthcare provider may order one or both based on your symptoms and medical history.