Comparison of clinical outcomes using activated partial thromboplastin time versus antifactor-Xa for monitoring therapeutic unfractionated heparin: A systematic review and meta-analysis

Introduction: Continuous intravenous unfractionated heparin (UFH) is a mainstay of therapeutic anticoagulation in the acute setting. The two most common laboratory tests for monitoring UFH are the activated partial thromboplastin time (aPTT) and antifactor Xa (anti-Xa) heparin assay. We reviewed the available evidence to evaluate if the choice of monitoring test for UFH therapy is associated with a difference in the clinical outcomes of bleeding, thrombosis, or mortality. Materials and methods: MEDLINE, Cochrane database, and conference abstracts from the Society of Critical Care Medicine, the American Society of Hematology, and the American College of Clinical Pharmacy were searched for all studies comparing aPTT and anti-Xa monitoring for therapeutic UFH that evaluated outcomes for bleeding, thrombotic events, or mortality. Risk of bias was assessed with the Cochrane Risk of Bias Tool and Newcastle Ottawa Scale. Pooled relative risk ratios were calculated using an inverse variance-weighted random-effects model. Results: Ten studies (n = 6677) were included for analysis. The use of anti-Xa compared to aPTT was not associated with an increased risk of bleeding (RR 1.03; 95% CI 0.8-1.22 I2 = 4%) or an increased risk of thrombotic events (RR 0.99; 95% CI 0.76-1.30, I2 = 3%). There was no difference in mortality within individual studies but the data were not suitable for pooled analysis. Conclusions: Pooled data comparing aPTT vs. anti-Xa for monitoring therapeutic UFH did not suggest differences in the outcomes of bleeding or thrombosis.