APTT measurement is the most commonly used clinically sensitive screening test to reflect the coagulation activity of the endogenous coagulation system. It is used to detect endogenous coagulation factor defects and related inhibitors and to screen the phenomenon of activated protein C resistance. It has a wide range of applications in terms of inspection, monitoring of heparin therapy, early diagnosis of disseminated intravascular coagulation (DIC), and preoperative examination.