Final answer:
Citrate is the anticoagulant used when running an APTT and PT test, as it prevents clotting by binding to calcium ions without impacting clotting factors used in these tests.
Step-by-step explanation:
When running an APTT (Activated Partial Thromboplastin Time) and PT (Prothrombin Time) test, the anticoagulant that is used is citrate. These tests are designed to measure the efficiency of the blood's coagulation pathways, and citrate functions by binding to calcium ions in the blood, thereby preventing clotting. It is important to note that while EDTA also binds to calcium, it is not used for these tests because it can irreversibly impact the clotting factors. Drugs like Heparin and Coumadin are therapeutic anticoagulants used in various medical treatments but are not suitable as additives for these laboratory tests.