To the Editor We read the article by Smyth et al1 with interest. The authors performed a large meta-analysis to determine whether participants in large, multicenter dialysis trials were similar to the general population undergoing dialysis in terms of age, comorbidities, and mortality rate. They concluded that participants in large, multicenter randomized clinical trials of patients with end-stage kidney disease undergoing dialysis are younger, have a different pattern of comorbidities, and have a lower mortality rate than the general population of patients undergoing dialysis. This finding has implications for the generalization of trial results to the broader patient population and for future trial design. However, after carefully reading the article, we are concerned that studies making use of the same cohort of patients were included multiple times in the analysis. There were several studies described in eTable 1 in the Supplement that look quite likely to be making use of the same cohort of patients.
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Jiang M, Lin Y, Su S. Studies Making Use of the Same Randomized Clinical Trial Cohorts. JAMA Intern Med. 2019;179(10):1446–1447. doi:10.1001/jamainternmed.2019.4621
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