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How well is the clinical importance of study results reported? An assessment of randomized controlled trials

Chan KB, Man-Son-Hing M, Molnar FJ, Laupacis A. CMAJ. 2001; 165(9):1197-202.

Background — The interpretation of the results of randomized controlled trials (RCTs) has traditionally emphasized statistical significance rather than clinical importance. Our aim was to assess the quality of reporting of factors related to clinical importance in a sample of published RCTs.

Methods — A random sample of 27 (of a total of 266) RCTs published in 5 major medical journals over a 1-year period were reviewed by 4 independent reviewers for factors considered important in the interpretation of the clinical importance of study results: identification of a clearly defined primary outcome, reporting of the expected difference between groups used in the calculation of sample size (the delta value) and whether it was based on the minimal clinically important difference of the intervention, the statistical significance of the results, presentation of pertinent confidence intervals, and the authors' interpretation of the clinical importance of the results.

Results — Twenty-two of 27 (81%) articles explicitly reported a single primary outcome. Of the 20 articles that included a sample size calculation, 18 (90%) reported a delta value. Two of the 18 (11%) articles explicitly stated that the delta value was chosen to reflect the minimal clinically important difference of the intervention. For the primary outcomes, confidence intervals surrounding the point estimates of the efficacy of the interventions were reported in 11 of 27 (41%) studies. The study results were interpreted from the perspective of clinical importance in 20 of 27 (74%) of the articles. Of these 20 reports, 5 (25%) provided justification for their clinical interpretation of the results.

Interpretation — Authors of RCTs published in major general medical and internal medicine journals do not consistently provide their own interpretation of the clinical importance of their results, and they often do not provide sufficient information to allow readers to make their own interpretation.

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Keywords: Research and statistical methods