Value of flow diagrams in reports of randomized controlled trials.

CONTEXT Diagrams of the flow of participants through a clinical trial are recommended in the Consolidated Standards for Reporting of Trials (CONSORT) statement, but it is unclear whether such flow diagrams improve the quality of trial reports. OBJECTIVE To examine the information contributed by flow diagrams and the completeness of reporting overall in reports of randomized controlled trials (RCTs) published in 5 general and internal medicine journals. DESIGN AND SETTING Analysis of 270 reports of RCTs published in 1998 in the Annals of Internal Medicine (AIM; n = 19), BMJ (n = 42), JAMA (n = 45), The Lancet (n = 81), and The New England Journal of Medicine (NEJM; n = 83). MAIN OUTCOME MEASURES Proportion of reports that included a flow diagram, information provided in flow diagrams, and completeness of reporting about flow of participants overall in flow diagrams or text. RESULTS A total of 139 reports (51.5%) of RCTs included a flow diagram, but this varied widely among journals (AIM, 21.0%; BMJ, 38.1%; JAMA, 80.0%; The Lancet, 93.8%; and NEJM, 8.4%). Diagrams generally provided useful information, but only 73 (52.5%) included the number of participants who received allocated interventions and only 32 (23.0%) included the number of participants included in the analysis. In logistic regression analysis, overall completeness of reporting about flow of study participants was associated with publication of a flow diagram. CONCLUSIONS Flow diagrams are associated with improved quality of reporting of randomized controlled trials. However, the structure of current flow diagrams is less than ideal. We propose a revised flow diagram that includes all important counts through the stages of parallel group trials.