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Psychooncology. 2013 Aug;22(8):1738-47. doi: 10.1002/pon.3205. Epub 2012 Oct 18.

Designing psycho-oncology randomised trials and cluster randomised trials: variance components and intra-cluster correlation of commonly used psychosocial measures.

Author information

1
Psycho-Oncology Co-operative Research Group, University of Sydney, Sydney, Australia. melanie.bell@sydney.edu.au

Abstract

OBJECTIVE:

The study aims to provide information about variance components of psychosocial outcomes: within and between-participant variance, within-participant correlation and for cluster randomised trials, the intra-cluster correlation (ICC) and, also, to demonstrate how estimates of these variance components and ICCs can be used to design randomised trials and cluster randomised trials.

METHOD:

Data from 15 longitudinal multi-centre psycho-oncology studies were analysed, and variance components including ICCs were estimated. Studies with psychosocial outcomes that had at least one measurement post-baseline including individual randomised controlled trials, cluster randomised trials and observational studies were included.

RESULTS:

Variance components and ICCs from 87 outcome measures were estimated. The unadjusted, single timepoint (first post-baseline) ICCs ranged from 0 to 0.16, with a median value of 0.022 and inter-quartile range 0 to 0.0605. The longitudinal ICCs ranged from 0 to 0.09 with a median value of 0.0007 and inter-quartile range 0 to 0.018.

CONCLUSIONS:

Although the magnitude of variance components and ICCs used for sample-size calculation cannot be known in advance of the study, published estimates can help reduce the uncertainty in sample-size calculations. Psycho-oncology researchers should be conservative in their sample-size calculations and use approaches that improve efficiency in their design and analysis.

KEYWORDS:

ICC; cancer; design; longitudinal; oncology; statistical methodology

PMID:
23080401
DOI:
10.1002/pon.3205
[Indexed for MEDLINE]

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