What is the therapeutic range for the aPTT test?
Studies have established a therapeutic range for the aPTT test, with an aPTT ratio of 1.5 to 2.5 corresponding to a heparin level of 0.2 to 0.4 units by protamine titration and a heparin level of 0.3 to 0.7 units measured by an anti-Xa assay. However, the measured response to the aPTT varies between reagents and instruments used to measure the aPTT, and the therapeutic aPTT range at a particular institution should be adapted to the responsiveness of the reagent and coagulometer used.