Comparison of unfractionated heparin protocols using antifactor Xa monitoring or activated partial thrombin time monitoring (Reprinted from Journal of Health-System Pharmacy Residents JHPR, vol 1, issue 2, 2012)

Objective. To determine whether there is a difference between an activated partial thromboplastin time (aPTT) based unfractionated heparin (UFH) protocol versus an antifactor Xa based UFH protocol with respect to 24-hour attainment of therapeutic levels. Methods. This was an observational study performed at a 500 bed private, community hospital. The study included inpatients from January 2008 to December 2009 on our institution's aPTT UFH protocol and inpatients from July 2010 to March 2011 on our institution's antifactor Xa UFH protocol. The two groups were compared to determine whether a higher percentage of patients reached therapeutic goal within 24 hours of UFH initiation. Secondary outcomes evaluated the percentage of patients at therapeutic goal within 6 and 12 hours, incidence of bleeding, and number of UFH dosage adjustments within 24 hours between the two groups. Results. One hundred twenty-one patients met inclusion criteria for this study; 79 in the aPTT group and 42 in the antifactor Xa group. At 24 hours, 74% of patients in the antifactor Xa group were at goal, versus 63% of patients in the aPTT group (p = 0.242). Nearly 57% of patients in the antifactor Xa group were at goal versus 27% in the aPTT group within 6 hours (p = 0.001). Subjects in the antifactor Xa group averaged 1.00 dosage adjustments per subject as compared to an 1.71 dosage adjustments per subject in the aPTT group within the first 24 hours (p = 0.003). Conclusion. The antifactor Xa assay should be used to monitor UFH versus aPTT due to less variability in measurements, the absence of a need for calibration with new reagents/coagulometers, quicker attainment of therapeutic levels, fewer dose adjustments, and similar bleeding rates.