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Acetylsalicylic Acid versus Low-Molecular-Weight Heparin for Venous Thromboembolism Prophylaxis: Comparative Clinical Effectiveness and Guidelines

Last updated: November 14, 2017
Project Number: RC0941-000
Product Line: Rapid Response
Research Type: Drug
Report Type: Summary with Critical Appraisal
Result type: Report

Question

  1. What is the comparative clinical effectiveness of acetylsalicylic acid versus low-molecular-weight heparin for venous thromboembolism prophylaxis in patients undergoing total hip or knee replacement?
  2. What is the comparative clinical effectiveness of acetylsalicylic acid versus factor Xa inhibitors with or without addition of mechanical compression for venous thromboembolism prophylaxis in patients undergoing total hip or knee replacement?
  3. What are the evidence-based guidelines on the use of acetylsalicylic acid or low-molecular-weight heparin for venous thromboembolism prophylaxis in patients undergoing total hip or knee replacement?

Key Message

Five systematic reviews (including two network meta-analyses) and five non-randomized primary clinical studies provided low- to moderate-quality evidence regarding the clinical effectiveness of acetylsalicylic acid (ASA) compared to low-molecular-weight heparin (LMWH) or factor Xa inhibitors (FXaIs) for venous thromboembolism prophylaxis in patients undergoing total hip or knee replacement surgery. In general, findings were inconsistent; although the majority of the evidence suggested that ASA had similar clinical effectiveness and safety compared to LMWH or FXaIs, some comparisons favoured ASA and others favoured LMWH or FXaIs. These inconsistencies may be related to differences in study design, patient characteristics, treatment regimens, or other factors, and additional high-quality studies are needed in order to provide definitive conclusions regarding the comparative clinical effectiveness of ASA versus LMWH and FXaIs. One guideline, based on low- to moderate-quality evidence, was identified that provides a strong recommendation to use of any one of the following prophylactic treatments for patients undergoing total hip or knee replacement surgery: LMWH, FXaIs (fondaparinux, apixaban, dabigataran, or rivaroxaban), low-dose unfractionated heparin, adjusted-dose vitamin K antagonist, aspirin (i.e., ASA) or an intermittent pneumatic compression device (IPCD). Additionally, the guideline provides weak recommendations for: the use of LMWH over the alternatives; the combination of pharmacological prophylaxis with an IPCD; and the use of an IPCD or no prophylaxis in patients at increased risk of bleeding.