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- Title
Sample size considerations for stratified cluster randomization design with binary outcomes and varying cluster size.
- Authors
Xu, Xiaohan; Zhu, Hong; Ahn, Chul
- Abstract
Stratified cluster randomization trials (CRTs) have been frequently employed in clinical and healthcare research. Comparing with simple randomized CRTs, stratified CRTs reduce the imbalance of baseline prognostic factors among different intervention groups. Due to the popularity, there has been a growing interest in methodological development on sample size estimation and power analysis for stratified CRTs; however, existing work mostly assumes equal cluster size within each stratum and uses multilevel models. Clusters are often naturally formed with random sizes in CRTs. With varying cluster size, commonly used ad hoc approaches ignore the variability in cluster size, which may underestimate (overestimate) the required number of clusters for each group per stratum and lead to underpowered (overpowered) clinical trials. We propose closed-form sample size formulas for estimating the required total number of subjects and for estimating the number of clusters for each group per stratum, based on Cochran-Mantel-Haenszel statistic for stratified cluster randomization design with binary outcomes, accounting for both clustering and varying cluster size. We investigate the impact of various design parameters on the relative change in the required number of clusters for each group per stratum due to varying cluster size. Simulation studies are conducted to evaluate the finite-sample performance of the proposed sample size method. A real application example of a pragmatic stratified CRT of a triad of chronic kidney disease, diabetes, and hypertension is presented for illustration.
- Subjects
MULTILEVEL models; KIDNEY diseases; SAMPLE size (Statistics); CLINICAL trials; TREATMENT of chronic kidney failure; CHRONIC kidney failure complications; HYPERTENSION; COMPUTER simulation; STATISTICS; RANDOMIZED controlled trials; MEDICAL protocols; STATISTICAL sampling; CLUSTER analysis (Statistics); DIABETIC nephropathies; DIABETIC angiopathies; DISEASE complications
- Publication
Statistics in Medicine, 2019, Vol 38, Issue 18, p3395
- ISSN
0277-6715
- Publication type
journal article
- DOI
10.1002/sim.8175