Which tests determine the clotting tendency of blood?

• A. T4/TSH
• B. Troponin
• C. PT/PTT
• D. UA

Answer: (C)

Clotting tendency is assessed with coagulation tests that measure how long blood takes to form a clot. The best choice combines two standard measures: prothrombin time and partial thromboplastin time. Prothrombin time looks at the extrinsic pathway and the common pathway of coagulation, reflecting factors II, VII, X, and I, and can be influenced by vitamin K status or Warfarin therapy. Partial thromboplastin time examines the intrinsic pathway and the common pathway, involving factors VIII, IX, XI, XII, and the same common pathway factors, and is often used to monitor heparin therapy or to detect deficiencies or inhibitors. Abnormal results suggest a coagulation issue, such as factor deficiencies or anticoagulant effects. The other options aren’t about blood clotting: thyroid tests (T4/TSH), a cardiac injury marker (troponin), and urine analysis (UA) do not assess how quickly blood clots.