In total, 38 trials met eligibility criteria. Only one considered cost-effectiveness in sample size calculations. RCTs were less likely to reach definitive conclusions based on the cost-effectiveness results than the primary clinical outcome (15.8% vs. 42.1%; McNemar; p = 0.01). In trials that provided sufficient data, exploratory analysis indicated that the median power to detect important differences was 29.5% for QALYs, 94.1% for costs, and 78.7% for the primary clinical outcome. In three trials (7