Prior to a surgery, certain blood tests may be ordered to determine the effectiveness of the body’s ability to perform the process of blood coagulation. These tests are collectively referred to as a coagulation study. Coagulation studies include the measurement of Prothrombin Time or PT; Partial Thromboplastin Time or PTT; and International Normalized Ratio or INR. In certain surgical procedures, the blood may be required not to coagulate as quickly as it normally does. In such cases, medication may be administered to slow down the coagulation time. In other instances, the blood may be unable to clot as quickly as it should and as such treatment may be administered to bring about quicker coagulation of the blood.
This is the most common type of test done in blood coagulation studies. It is usually performed prior to a surgery in order to determine the level of blood clotting ability. This helps to detect if there is likely to be a problem of bleeding or clotting during or subsequent to a surgery. It is also measured to detect the cause of excessive bruising or bleeding, to determine the effectiveness of blood thinning therapy, to evaluate the functioning of the liver and to detect the levels of blood coagulation factors. Normal PT values are between 10 to 12 seconds. Common factors resulting in a prolonged prothrombin time are vitamin K deficiencies, liver disease, disseminated intravascular intervention, hormone replacement drugs, oral contraceptives or use of anti-coagulant medication.
The partial thromboplastin time (PTT) or activated partial thromboplastin time (APTT) test is done to determine the effectiveness of blood thinning or heparin therapy. Clotting disorders can also be detected with the help of this test. Normal PTT values are between 30 to 45 seconds. Prolonged PTT values can occur because of anticoagulation medication, lupus, liver disorders and conditions that cause impaired coagulation.
An International Normalized Ratio or INR blood test is performed to ensure consistency of PT test results from across different labs. This is because an individual’s PT test results may differ from one lab to another depending on the manner in which the test was performed. As such individuals undergoing treatment in different locations would face a problem as what may be termed as normal results in one lab would not be considered so in another lab. The INR test results have to be consistent, no matter where the tests are taken. The normal INR values are 1 to 2.