What is the therapeutic aPTT range at a particular institution?
The therapeutic aPTT range at a particular institution should be adapted to the responsiveness of the reagent and coagulometer used. Depending on the reagent and coagulometer, aPTT results ranging from 48 to 108 s can be measured in samples with a heparin concentration of 0.3 units/mL, as determined using an anti-Xa assay. With heparin levels of 0.3 to 0.7 anti-Xa units/mL, modern aPTT reagents and coagulometers produce aPTT ratios that range from 1.5 to 2.5. Various heparin dose-adjustment nomograms have also been developed to help determine the therapeutic aPTT range for a particular institution. However, none is applicable to all aPTT reagents. Therefore, the therapeutic aPTT range at a particular institution should be adapted to the responsiveness of the reagent and coagulometer used.  