Coagulation factor tests are a group of blood tests that measure the activity and levels of various proteins involved in blood clotting. These tests are used to assess the risk of bleeding or clotting disorders, monitor treatment effectiveness in patients with such disorders, and diagnose or monitor liver disease.

Some commonly ordered coagulation factor tests include:

1. Prothrombin time (PT): This test measures the time it takes for blood to clot after adding a clotting agent called thromboplastin. It assesses the function of factors I (fibrinogen), II (prothrombin), V, VII, and X.

2. Partial thromboplastin time (PTT): This test measures the time it takes for blood to clot after adding a clotting agent called partial thromboplastin. It assesses the function of factors I, II, V, VIII, IX, X, XI, and XII.

3. International normalized ratio (INR): This test is used to standardize PT results between different laboratories, as different thromboplastin reagents may have varying sensitivities. It is commonly used to monitor patients taking anticoagulant therapy.

4. Factor assays: These tests measure the levels of individual clotting factors, such as factor VIII or IX, in the blood. They are used to diagnose specific bleeding or clotting disorders, monitor treatment effectiveness, and assess the risk of bleeding before surgery.

5. Platelet function tests: These tests assess how well platelets in the blood are functioning and sticking together to form clots. Examples include platelet aggregation studies and bleeding time tests. They are used to diagnose platelet function disorders and monitor antiplatelet therapy.

Coagulation factor tests are typically ordered by a healthcare provider if a patient has a personal or family history of bleeding or clotting disorders, unexplained bruising or bleeding, or liver disease. Depending on the results, further testing or treatment may be recommended.