Cluster-randomized trials of cancer screening interventions: Has use of appropriate statistical methods increased over time?

Abstract

Background: In a cluster randomized trial, groups of individuals (e.g., clinics, schools) are randomized to conditions. The design and analysis of cluster randomized trials can require more care than individually randomized trials. Past reviews have noted deficiencies in the use of appropriate statistical methods for such trials.

Methods: We reviewed cluster randomized trials of cancer screening interventions published 1995-2019 to determine whether appropriate statistical methods had been used for sample size calculation and outcome analysis and whether they reported intraclass correlation coefficient (ICC) values. This work expanded a previous review of articles published 1995-2010.

Results: Our search identified 88 articles published 1995-2020 that reported outcomes of cluster randomized trials of breast, cervix, and colorectal cancer screening interventions. There was increased reporting of the trials' sample size calculations over time, with the percentage increasing from 31% in 1995-2004 to 77% in 2014-2019. However, the percentage of calculations failing to account for cluster randomization did not change over time and was 17% of studies in 2014-2019. There was a nonsignificant trend towards increased use of outcome analysis methods that accounted for the cluster randomized design. However, in lower impact journals, use of appropriate analysis methods was only 80% in 2014-2019. Only 33% of studies reported ICC values in 2014-2019.

Conclusion: For cluster randomized trials with cancer screening outcomes, there have been improvements in the reporting of sample size calculations but methodological and reporting deficiencies persist. Efforts to disseminate, adopt and report the use of appropriate statistical methodologies are still needed.

Keywords: CONSORT; Cancer screening intervention trials; Cluster randomized trials; Intraclass correlation coefficient.