The PTT is often used in conjunction with another measure of how quickly blood clotting takes place called the prothrombin time (PT).

Activated partial thromboplastin time (APTT) is typically analyzed by a medical technologist or laboratory technician, either manually or using an automated instrument at 37°C, which approximates normal human body temperature.

Prothrombin time utilizes complete thromboplastin, a combination of tissue factor and phospholipids.

[4] Normal PTT requires the presence of the following coagulation factors: I, II, V, VIII, IX, X, XI and XII.

[8] The partial thromboplastin time was first described in 1953 by researchers at the University of North Carolina at Chapel Hill.