Update on the collaborative interventions for circulation and depression (COINCIDE) trial: changes to planned methodology of a cluster randomized controlled trial of collaborative care for depression in people with diabetes and/or coronary heart disease

Background: The COINCIDE trial aims to evaluate the effectiveness and cost-effectiveness of a collaborative care intervention for depression in people with diabetes and/or coronary heart disease attending English general practices. Design: This update details changes to the cluster and patient recruitment strategy for the COINCIDE study. The original protocol was published in Trials (http://www.trialsjournal.com/content/pdf/1745-6215-13-139.pdf). Modifications were made to the recruitment targets in response to lower-than-expected patient recruitment at the first ten general practices recruited into the study. In order to boost patient numbers and retain statistical power, the number of general practices recruited was increased from 30 to 36. Follow-up period was shortened from 6 months to 4 months to ensure that patients recruited to the trial could be followed up by the end of the study. Results: Patient recruitment began on the 01/05/2012 and is planned to be completed by the 30/04/2013. Recruitment for general practices was completed on 31/10/2012, by which time the target of 36 practices had been recruited. The main trial results will be published in a peer-reviewed journal. Conclusion: The data from the trial will provide evidence on the effectiveness and cost-effectiveness of collaborative care for depression in people with diabetes and/or coronary heart disease. Trial registration: Trial registration number: ISRCTN80309252