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Cluster randomised trials

  • C. Barbui (a1) and A. Cipriani (a1)

Abstract

Although randomised controlled trials are the reference methodology to assess the effects of therapeutic interventions, for interventions that naturally occur in groups of individuals random allocation of participants may be inappropriate. In these cases, the unit of random allocation may be the group or cluster, rather than the individual. Clinical trials that randomly allocate groups or clusters of individuals are called cluster randomised trials. This article briefly presents the main implications of cluster randomisation with respect to the following methodological aspects: generalisability, concealment of allocation, comparability at baseline, blindness, loss of clusters and intra-class correlation.

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Copyright

Corresponding author

*Address for correspondence: Professor Corrado Barbui, Department of Public Health and Community Medicine, Section of Psychiatry and Clinical Psychology, University of Verona, Piazzale L.A. Scuro, 10-37134 Verona, Italy. (Email: corrado.barbui@univr.it)

Footnotes

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This Section of Epidemiology and Psychiatric Sciences regularly appears in each issue of the Journal to cover methodological aspects related to the design, conduct, reporting and interpretation of clinical and epidemiological studies. The aim of these Editorials is to help developing a more critical attitude towards research findings published in international literature, promoting original research projects with higher methodological standards, and implementing the most relevant results of research in every-day clinical practice.

Corrado Barbui, Section Editor and Michele Tansella, Editor EPS

Footnotes

References

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Campbell, MK, Elbourne, DR, Altman, DG (2004 a). CONSORT statement: extension to cluster randomised trials. British Medical Journal 328, 702708.
Campbell, MK, Grimshaw, JM, Elbourne, DR (2004 b). Intracluster correlation coefficients in cluster randomized trials: empirical insights into how should they be reported. BMC Medical Research Methodology 4, 9.
Campbell, MK, Thomson, S, Ramsay, CR, MacLennan, GS, Grimshaw, JM (2004 c). Sample size calculator for cluster randomized trials. Computers in Biology and Medicine 34, 113125.
Campbell, MK, Fayers, PM, Grimshaw, JM (2005). Determinants of the intracluster correlation coefficient in cluster randomized trials: the case of implementation research. Clinical Trials 2, 99107.
Cipriani, A, Barbui, C (2010). What is a clinical trial protocol? Epidemiologia e Psichiatria Sociale 19, 116117.
Cipriani, A, Nose, M, Barbui, C (2008). Allocation concealment and blinding in clinical trials. Epidemiologia e Psichiatria Sociale 17, 115116.
Eldridge, SM, Ashby, D, Feder, GS, Rudnicka, AR, Ukoumunne, OC (2004). Lessons for cluster randomized trials in the twenty-first century: a systematic review of trials in primary care. Clinical Trials 1, 8090.
Eldridge, S, Ashby, D, Bennett, C, Wakelin, M, Feder, G (2008). Internal and external validity of cluster randomised trials: systematic review of recent trials. British Medical Journal 336, 876880.
Eldridge, S, Kerry, S, Torgerson, DJ (2009). Bias in identifying and recruiting participants in cluster randomised trials: what can be done? British Medical Journal 339, b4006.
Hahn, S, Puffer, S, Torgerson, DJ, Watson, J (2005). Methodological bias in cluster randomised trials. BMC Medical Research Methodology 5, 10.
Puffer, S, Torgerson, D, Watson, J (2003). Evidence for risk of bias in cluster randomised trials: review of recent trials published in three general medical journals. British Medical Journal 327, 785789.
Puffer, S, Torgerson, DJ, Watson, J (2005). Cluster randomized controlled trials. Journal of Evaluation in Clinical Practice 11, 479483.
Purgato, M, Barbui, C, Cipriani, A (2010). Assessing risk of bias in randomized controlled trials. Epidemiologia e Psichiatria Sociale 19, 296297.
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Epidemiology and Psychiatric Sciences
  • ISSN: 2045-7960
  • EISSN: 2045-7979
  • URL: /core/journals/epidemiology-and-psychiatric-sciences
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