Abstract
Objective
To evaluate the power of responder analyses in a randomized controlled trial.
Study design and setting
Simulations were based on the Chronic Kidney Disease Antidepressant Sertraline Trial
(CAST), which compared sertraline to placebo for the treatment of depression in kidney disease.
Baseline disease severity, placebo response, effect size, and the proportion of responders
were varied across 72 scenarios. Power was assessed using a t-test for change scores, and the chi-square test for dichotomized outcomes of the minimal
important difference (MID), improvement and remission in 10,000 datasets with a fixed
sample size of 193.
Results
The t-test had >80% power except for scenarios with the lowest sertraline effect size. The
chi-square test using the MID had <7% power in all scenarios while improvement and
remission of achieved >80% power only at higher effect sizes and/or when the proportion
of responders was highest at 0.5. The chi-square test for improvement had marginal
power increases compared to the t-test (4/72 scenarios = 5.6%) and that for remission did not outperform the t-test in any scenario.
Conclusions
The t-test outperforms the chi-square test for dichotomized outcomes regardless of baseline
disease severity, placebo response, effect size and the proportion of responders to
the intervention.
Keywords
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Article info
Publication history
Published online: February 05, 2021
Accepted:
January 28,
2021
Footnotes
Conflict of interest: None.
Role of the funding source: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Identification
Copyright
© 2021 Elsevier Inc. All rights reserved.
