Extending the CONSORT statement to cluster randomized trials: for discussion.

The need for clear reporting of randomized controlled trials has been emphasized recently. The CONSORT Statement has made evidence-based suggestions for a checklist and a patient flow diagram. Adapting this for cluster randomized controlled trials presents particular challenges. Simple changes in the checklist and diagram for the completely randomized two level cluster randomized trials are suggested for discussion. An example taken from an unpublished trial demonstrates that these changes are less simple to implement, although extensions to electronic publications may be helpful. These suggestions should be formally evaluated. Further work is required to consider the cases of more levels and of stratified or pair-matched cluster randomized trials.