Activated partial thromboplastin time after heparin removal (aPTT/HR) in a new scheme of anticoagulant monitoring

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Abstract
Activated partial thromboplastin time after heparin removal (aPTT/HR), a test employing anion exchange chromatography, was devised as an alternative to the prothrombin time after heparin removal (PT/HR) to monitor simultaneous anticoagulation with heparin and coumarins. The potential utility of the aPTT/HR was assessed by performing parallel PTs and aPTTs on 62 consecutive plasmas from coumarin‐treated outpatients. All samples had 0.2 units/ml of heparin added and then removed to see if the maneuver influenced therapeutic group assignment. In no instance did reassignment occur. A conditional Irwin‐Fisher test (P = 0.000604) and a special multinomial trial analysis (P = 0.002) indicated that the aPTT would be at least comparable to the PT for following coumarin antithrombotic prophylaxis. Since the heparin removal procedure had no influence on therapeutic categorization, the same statistical proof could be applied to the relationship between aPTT/HR and PT/HR. This study indicates that the aPTT can be used to monitor all stages of heparin and/or coumarin anticoagulation.