Clotting, activated partial thromboplastin and coagulation times in monitoring heparin therapy

The automated-activated coagulation time, manual-activated coagulation tim e and the activated partial throm boplastin time were compared to the whole blood clotting tim e in the m easurem ent of hypocoagulation of heparin ized blood. The normal ranges and degree of reproducibility were determ ined for each clotting assay. Each m ethod was examined for its sensi­ tivity to various concentrations of heparin. In addition, blood samples from patients treated with heparin were assayed by all four m ethods and their results were compared. The results indicated that the manual-activated clotting tim e correlated best with the whole blood clotting tim e, was sensi­ tive to low concentrations of heparin, formed a discernible clot w ithin a convenient tim e period in blood containing high concentrations of heparin, was reproducible and was easily performed.