Comparing methods of establishing the aPTT therapeutic range of heparin.

Background: The American College of Chest Physicians (ACCP) recommends that the activated partial thromboplastin time (aPTT) therapeutic range for unfractionated heparin be defined as the aPTT corresponding to a heparin concentration of 0.3-0.7 micro/mL by heparin anti-factor Xa assay.