Use of the activated partial thromboplastin time in the control of heparin administration.

H EPARIN, which acts as a direct anticoagulant, in contrast to indirect anticoagulants such as the coumarins or indandiones, has been thought by some investigators to fulfill more nearly the role of tile ideal anticoagulant (1-3). This naturally occurring mucopolysaccharide rapidly decreases the activity of the coagulation system by acting both as an antithromboplastin and as an antithrombin. It has possible further advantages in acting as a clearing factor, a lipase enzyme activator, an anti-inflammatory agent and an antihistaminic (4-5). Heparin treatment has been reported to be safer than coumarin type anticoagulants during pregnancy since heparin does not cross the placental barrier (6, 7). One of the disadvantages associated with heparin ti#{236}erapy has been the lack of a convenient and satisfactory control procedure. The whole blood clotting time (WBCT) has probably been the most widely used procedure for the control of heparin therapy. Belko and Warren (8) reported the superiority of the recalcification time, and ‘Struver et al. (9) suggested the use of the activated partial thromboplastin time (APTT) assay. The purpose of this work was to evaluate the APTT in comparison to the WBCT for the control of heparin administration.