PT and PTT
A blood clot forms following the successful and timely completion of a sequence of events known as the coagulation cascade, in which coagulation factors are activated one after the other. In order for the process to work effectively, an adequate quantity of each coagulation factor must be present, and each must function properly. An insufficient quantity can result in prolonged bleeding, while excess quantity can result in too much clotting. The PT test evaluates factors I, II, V, VII and X, while the PTT test evaluates factors I, II, V, VIII, IX, X, XI and XII, as well as prekallikrein (PK) and high molecular weight kininogen (HK). The combination of both tests examines how the factors work together, and evaluation of both results together can help diagnose certain conditions.
The PT and PTT Blood Tests are useful in the diagnosis of excessive, unexplained bleeding in patients who are not taking blood-thinning medications. These bleeding disorders include conditions such as nosebleeds, bruising, heavy menstrual periods, blood in the stool and/or urine, and bleeding gums, among others. The tests are also sometimes ordered for patients prior to surgery to ensure normal clotting ability.