COMMENTS AND RESPONSES Aspirin Versus Low-Molecular-Weight Heparin After Total

patients having elective total hip replacement in Canada during a 3-year period, Anderson and colleagues (1) observed how, after 10 days of dalteparin therapy, 28 days of oral aspirin prophylaxis was noninferior to 28 days of dalteparin therapy for preventing venous thromboembolism (VTE). These results are very interesting to clini-cians involved in elective hip surgery, particularly because some guidelines consider aspirin to be effective despite the single large randomized trial (2) quoted in the guidelines from the American College of Chest Physicians (3) that showed no effect of aspirin in this setting. We believe that the data from Anderson and colleagues ’ trial cannot be considered as definitive as the conclusions indicated. The randomization in this relatively small trial did not result in a satis-factory distribution of important risk factors. Despite the authors’ assurance of the similarity of baseline characteristics of the 2 groups