Monitoring Unfractionated Heparin Therapy with Antifactor Xa Activity Results in Fewer Monitoring Tests and Dosage Changes than Monitoring with the Activated Partial Thromboplastin Time

Abstract

STUDY OBJECTIVE: To determine how much more costly it is to monitor unfractionated heparin (UFH) therapy by antifactor Xa heparin activity (HA) than by activated partial thromboplastin time (aPTT). DESIGN: Prospective, randomized, unmasked, cohort, single-center study. SETTING: A 625-bed, adults-only, private teaching hospital. PATIENTS: Two hundred sixty-eight patients with a variety of indications for UFH therapy. INTERVENTIONS: Patients were treated with UFH based on ideal weight (75 U/kg bolus, 20 U/kg initial infusion) and monitored by either HA or aPTT, MEASUREMENTS AND MAIN RESULTS: After adjusting for gender, groups were equivalent in patient characteristics and UFH dosage. The HA group had fewer monitoring tests and dosage changes/24 hours than the aPTT group. These reductions neutralized much of the increased cost of the HA assay itself. CONCLUSION: Monitoring UFH therapy over 96 hours with an HA assay costs $4.37 more than monitoring with aPTT. This modest increase may be acceptable given other advantages of the HA assay.