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529250 
Journal Article 
Inadequate statistical power to detect clinically significant differences in adverse event rates in randomized controlled trials 
Tsang, R; Colley, L; Lynd, LD 
2009 
Yes 
Journal of Clinical Epidemiology
ISSN: 0895-4356 
62 
6 
609-616 
English 
Objective: To determine the statistical power to detect potentially clinically significant differences in serious adverse events between drug therapies reported in a sample of randomized controlled trials, (RCTs). Study Design and Setting: Systematic review of RCTs with positive efficacy endpoint and at least a twofold difference ill the proportion of patients with serious adverse events between treatment groups from six major journals. The power of each study to detect statistically significant differences in serious adverse events was calculated. Results: Of the six included trials, all performed statistical analysis oil adverse events without disclosure of the statistical power for detecting file reported differences between groups. The power of each study to detect the reported differences in adverse events, was calculated and yielded values ranging from 0.07 to 0.37 among trials with non-statistically significant differences. Conclusion: Statistical testing for differences in the proportion of patients experiencing in adverse event is common in RCTs: non-statistically significant differences are associated with low statistical power. A high probability of type II error may lead to errroneous clinical inference resulting in harm. The statistical power for nonsignificant tests should be considered in the interpretation of results. (C) 2009 Elsevier Inc. All rights reserved. 
Statistical power; Adverse events; Type II error; Beta error; Randomized controlled trials; Frequentist statistics; Statistical; significance; polycystic-ovary-syndrome; sample-size; ii error; rheumatoid-arthritis; surgical literature; beta errors; risk; metaanalysis