Which coagulation test measures the intrinsic clotting pathway?

Which coagulation test measures the intrinsic clotting pathway?

• A. Prothrombin time
• B. INR
• C. aPTT
• D. Platelet count

Answer: (C)

Activated partial thromboplastin time measures the intrinsic clotting pathway by using an activator and phospholipid to trigger the cascade through contact factors such as XII, XI, IX, and VIII. It mainly assesses the intrinsic arm and its progression into the common pathway. Prothrombin time uses tissue factor to initiate the extrinsic pathway and reflects the extrinsic and common pathways, not the intrinsic one. Platelet count looks at the number of platelets, not the enzymatic steps of coagulation. In practice, a prolonged aPTT suggests issues within the intrinsic pathway or its inhibitors, such as factor deficiencies (e.g., hemophilia) or the presence of inhibitors like lupus anticoagulant.

Activated partial thromboplastin time measures the intrinsic clotting pathway by using an activator and phospholipid to trigger the cascade through contact factors such as XII, XI, IX, and VIII. It mainly assesses the intrinsic arm and its progression into the common pathway. Prothrombin time uses tissue factor to initiate the extrinsic pathway and reflects the extrinsic and common pathways, not the intrinsic one. Platelet count looks at the number of platelets, not the enzymatic steps of coagulation. In practice, a prolonged aPTT suggests issues within the intrinsic pathway or its inhibitors, such as factor deficiencies (e.g., hemophilia) or the presence of inhibitors like lupus anticoagulant.