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Intra-cluster correlations from the CLustered OUtcome Dataset bank to inform the design of longitudinal cluster trials.

Publication ,  Journal Article
Korevaar, E; Kasza, J; Taljaard, M; Hemming, K; Haines, T; Turner, EL; Thompson, JA; Hughes, JP; Forbes, AB
Published in: Clin Trials
October 2021

BACKGROUND: Sample size calculations for longitudinal cluster randomised trials, such as crossover and stepped-wedge trials, require estimates of the assumed correlation structure. This includes both within-period intra-cluster correlations, which importantly differ from conventional intra-cluster correlations by their dependence on period, and also cluster autocorrelation coefficients to model correlation decay. There are limited resources to inform these estimates. In this article, we provide a repository of correlation estimates from a bank of real-world clustered datasets. These are provided under several assumed correlation structures, namely exchangeable, block-exchangeable and discrete-time decay correlation structures. METHODS: Longitudinal studies with clustered outcomes were collected to form the CLustered OUtcome Dataset bank. Forty-four available continuous outcomes from 29 datasets were obtained and analysed using each correlation structure. Patterns of within-period intra-cluster correlation coefficient and cluster autocorrelation coefficients were explored by study characteristics. RESULTS: The median within-period intra-cluster correlation coefficient for the discrete-time decay model was 0.05 (interquartile range: 0.02-0.09) with a median cluster autocorrelation of 0.73 (interquartile range: 0.19-0.91). The within-period intra-cluster correlation coefficients were similar for the exchangeable, block-exchangeable and discrete-time decay correlation structures. Within-period intra-cluster correlation coefficients and cluster autocorrelations were found to vary with the number of participants per cluster-period, the period-length, type of cluster (primary care, secondary care, community or school) and country income status (high-income country or low- and middle-income country). The within-period intra-cluster correlation coefficients tended to decrease with increasing period-length and slightly decrease with increasing cluster-period sizes, while the cluster autocorrelations tended to move closer to 1 with increasing cluster-period size. Using the CLustered OUtcome Dataset bank, an RShiny app has been developed for determining plausible values of correlation coefficients for use in sample size calculations. DISCUSSION: This study provides a repository of intra-cluster correlations and cluster autocorrelations for longitudinal cluster trials. This can help inform sample size calculations for future longitudinal cluster randomised trials.

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Published In

Clin Trials

DOI

EISSN

1740-7753

Publication Date

October 2021

Volume

18

Issue

5

Start / End Page

529 / 540

Location

England

Related Subject Headings

  • Statistics & Probability
  • Sample Size
  • Research Design
  • Primary Health Care
  • Longitudinal Studies
  • Humans
  • Cross-Over Studies
  • Cluster Analysis
  • 5203 Clinical and health psychology
  • 4905 Statistics
 

Citation

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ICMJE
MLA
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Korevaar, E., Kasza, J., Taljaard, M., Hemming, K., Haines, T., Turner, E. L., … Forbes, A. B. (2021). Intra-cluster correlations from the CLustered OUtcome Dataset bank to inform the design of longitudinal cluster trials. Clin Trials, 18(5), 529–540. https://doi.org/10.1177/17407745211020852
Korevaar, Elizabeth, Jessica Kasza, Monica Taljaard, Karla Hemming, Terry Haines, Elizabeth L. Turner, Jennifer A. Thompson, James P. Hughes, and Andrew B. Forbes. “Intra-cluster correlations from the CLustered OUtcome Dataset bank to inform the design of longitudinal cluster trials.Clin Trials 18, no. 5 (October 2021): 529–40. https://doi.org/10.1177/17407745211020852.
Korevaar E, Kasza J, Taljaard M, Hemming K, Haines T, Turner EL, et al. Intra-cluster correlations from the CLustered OUtcome Dataset bank to inform the design of longitudinal cluster trials. Clin Trials. 2021 Oct;18(5):529–40.
Korevaar, Elizabeth, et al. “Intra-cluster correlations from the CLustered OUtcome Dataset bank to inform the design of longitudinal cluster trials.Clin Trials, vol. 18, no. 5, Oct. 2021, pp. 529–40. Pubmed, doi:10.1177/17407745211020852.
Korevaar E, Kasza J, Taljaard M, Hemming K, Haines T, Turner EL, Thompson JA, Hughes JP, Forbes AB. Intra-cluster correlations from the CLustered OUtcome Dataset bank to inform the design of longitudinal cluster trials. Clin Trials. 2021 Oct;18(5):529–540.
Journal cover image

Published In

Clin Trials

DOI

EISSN

1740-7753

Publication Date

October 2021

Volume

18

Issue

5

Start / End Page

529 / 540

Location

England

Related Subject Headings

  • Statistics & Probability
  • Sample Size
  • Research Design
  • Primary Health Care
  • Longitudinal Studies
  • Humans
  • Cross-Over Studies
  • Cluster Analysis
  • 5203 Clinical and health psychology
  • 4905 Statistics