A medical test that doctors order for patients on anticoagulant drug therapy, the most common being Coumadin for people with heart disease risk. It tests the clotting time of the blood because the over dosing of blood thinners can cause excess bleeding or bruising. Thromboplastin and calcium are added to the decalcified plasma. This test is usually abbreviated as protime. Asprin is also a blood thinner and one a day, or a baby asprin a day is often prescribed for people at risk.