1. APTT

　　The Heparins Manufacturer describes APTT as still one of the options for monitoring UFH. It is very simple, fast and cheap project. However, it is difficult to standardize. The APTT test requires that all proteins in the entire clotting waterfall be intact to accurately measure heparin levels.

　　2. Neutralization test of protamine sulfate

　　The experiment is based on the principle that UFH, a highly negatively charged molecule, is neutralized by protamine sulfate, a positively charged protein. Different concentrations of protamine sulfate were added into plasma, and then thrombin was added to measure the coagulation time. A return of thrombin coagulation time to normal protamine sulfate concentration is considered to be heparin concentration.

　　3. Anti-xa activity detection

　　The principle of detecting the anti-XA activity of heparin by hair substrate method is the same: Heparin in the specimen forms a complex with AT to inhibit the excessive addition of factor Xa. The remaining factor Xa activity was measured by its interaction with specific substrates to release pNA.