When and how should we cluster and cross over: methodological and ethical issues (letter 2)
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To the Editor,
Goldstein et al.1 express their “concerns regarding the methodological and ethical issues raised in trials such as the B-Free trial”. Correspondence from Spence et al.2 responds to the ethical issues raised; we would like to respond to the methodological issues. Specifically, Goldstein et al. mention the following concerns: (i) increases in Type I error, (ii) limited external validity, (iii) imbalance in baseline characteristics, and (iv) carry-over and period effects. In designing the Benzodiazepine-Free Cardiac Anesthesia for Reduction in Postoperative Delirium (B-Free) trial, we accounted for these methodological issues.3
Cluster-randomized trials could result in inflated Type I error because analyses are conducted at the individual level but randomization is at the cluster level and members of the same cluster tend to have more similar responses than members of different clusters. Therefore, it is crucial to account for the effect of clustering in sample size...
Financial disclosure and conflict of interest
This submission was handled by Dr. Gregory L. Bryson, Deputy Editor-in-Chief, Canadian Journal of Anesthesia.
- 2.Spence J, Belley-Côté E, Ozchowski S, et al. When and how should we cluster and cross over: methodological and ethical issues (letter 1). Can J Anesth 2018; 65: DOI: https://doi.org/10.1007/s12630-018-1237-5.
- 3.Spence J, Belley-Côté E, Lee SF, et al. The role of randomized cluster crossover trials for comparative effectiveness testing in anesthesia: design of the Benzodiazepine-Free Cardiac Anesthesia for Reduction in Postoperative Delirium (B-Free) trial. Can J Anesth 2018; 65: 813-21.CrossRefGoogle Scholar
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