Activated Partial Thromboplastin Time Test (PTT)

The Activated Partial Thromboplastin Time Test which is generally called as the PTT test, is a test conducted in order to measure the ability of blood to clot under normal condition. It measures the amount of time taken by the blood to clot and checks for abnormalities in the blood. There are twelve different types of proteins which are involved in the process of blood clotting. The PTT measures the functioning of some these proteins. This test is also used to monitor heparin therapy.

PTT Reasons

The Active Partial Thromboplastin Time test is done to find out the cause behind abnormal bleeding or bruising and to check blood clotting time before a surgery. The test is also conducted to check for conditions causing clotting problems, to check for low level blood clotting factors and to see if the heparin (anti-clotting medicine) therapy is going right. There are many factors behind unusual blood clotting and other abnormalities in the blood such as Vitamin K deficiency, Factor VII deficiency or hemophilia A or B. The PTT test gives us the time taken by blood to clot. The normal clotting time is 25 to 30 seconds. If the values exceed in the test, then the person has abnormalities in the blood.

PTT Preparation

The health care provider may ask to stop the intake of certain medicines or drugs before taking the test. Some of the drugs which need to be stopped are antihistamines, Vitamin C, aspirin and Chlorpromazine. Consulting a doctor is necessary before stopping any kind of medication. The doctor may also advice you on other precautions that need to be taken before the test.

PTT Procedure

An elastic band is wrapped around the upper arm to stop the flow of blood and this makes the veins become larger and eases the process collecting blood by inserting a needle in the vein. A blood sample is thus collected and put in a vial. The elastic band is then removed. Cotton gauze or a cotton ball is placed over the inserted site. A bandage is put so as to apply pressure and stop further bleeding. The blood sample is sent to the laboratory to be tested. The laboratory specialist adds certain chemicals in the blood sample to see how much time it takes before the blood clots. A person on heparin therapy will be watched for signs of bleeding.