A prothrombin time (PT) is a blood test used to help identify & diagnose bleeding disorders or clotting disorders in your circulatory system. It tells you how long it takes your blood to clot. it’s used to monitor how well the blood-thinning medication (anticoagulant) is working to prevent blood clotting in your body.
Prothrombin is a protein made by the liver. It is one of the clotting (coagulation) factors. When you have a cut or injury, your clotting factors work together to form a blood clot. Low levels of clotting factors cause you to bleed too much after an injury. When clotting factor levels are too high, it can cause dangerous clots to form in your arteries or veins leading to thrombosis.
If you are not taking blood thinning medicines, we need to watch these values. The reference range for healthy individuals is: 11 to 13.5 seconds. Higher values than reference means it takes blood longer time than usual, to for clot & lower values indicate quicker blood clotting than normal.
When liver is not making the right amount of blood clotting proteins, clotting process takes longer. A high PT usually means that there is serious liver damage, vitamin K deficiency, or a coagulation factor deficiency (factor VII). Symptoms of a bleeding disorder include easy bruising, non-stop bleeding after applying pressure, heavy menstrual periods, blood in the urine, swollen or painful joints, nosebleeds etc. PT value is also a prognosis marker for cardiac patients. The anticoagulant drug, Warfarin is prescribed for people with a variety of conditions, such as deep vein thrombosis. PT is also used to check whether the medicine prescribed to prevent blood clots in your body is properly working or not.
Bleeding time depends on various factors such as functions of platelets, endothelial cells of arteries, pathways of coagulation. Clotting time is abnormally increased due to the absence or abnormality of clotting factors. Normally, APTT is also checked with PT for better diagnosis.