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
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.
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.
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.