What does PTT mean?

Hint: PTT is partial thromboplastin time. It is a kind of blood test. It is used to know how much time is needed for blood for clotting. It is useful to know whether a person has a bleeding problem. In addition, it informs if the blood is not clotted properly. Prothrombin time is a blood test related to PTT test. A blood sample is needed for performing the test.

Complete answer
PTT is estimated in seconds for the clot formation. Normal levels of PTT can vary between institutions and laboratories. However, the normal level of PTT is between $25$ to $35$. PTT is able to test for all clotting factors with the exception of factor VII, which is the tissue factor and factor XIII, which is the fibrin stabilizing factor.

Generally, PTT is used in clinical practice for monitoring patient response to unfractionated heparin infusion, for targeting therapeutic anticoagulation and becoming a part of “coagulation panel” for aiding in elucidation of causes of clotting and bleeding disorders.

Through standard phlebotomy technique, clinicians draw the blood sample from the vein of the patient. In a citrate-containing tube, which is generally light blue in color, the blood is collected. The citrate binds calcium, which inhibits clotting in the tube. This allows for effective extraction of plasma for testing. Infusion blood is collected every six hours for facilitation of dosing adjustments, for patients on continuous unfractionated heparin.

Note:
If blood-thinning medicines are taken by a person, he or she will be watched for signs of bleeding. Prolonged PTT means the longer time is needed for the clotting process to occur and it leads to the increased risk of blood clots. It indicates a low level of any blood clotting factors and another substance is needed for the clotting process. This may be due to bleeding disorders like haemophilia.