RESUMO
The activated partial thromboplastin time (APTT) test is widely used to monitor heparin anticoagulation. The relationship of the APTT to the activity of administered unfractionated heparin was defined in 23 patients on programmed hemodialysis, by using six APTT reagents. A calibration curve was plotted for each reagent. The heparinized and nonheparinized plasma values of APTT depended on the reagent being used. During clinical heparin therapy, an APTT-heparin concentration relationship was also defined by the used reagent. The reagents showed varying heparin sensitivity both in vitro and in vivo studies. APTT was estimated for the therapeutic application of heparin for all the reagents in the examinees. The authors consider it necessary to define an APTT-heparin concentration relationship for each reagent being used.