PABLO ALONSO-COELLO, MD 3SUMIT BHAGRA, MBBS 4 OBJECTIVE -We sought to systematically ascertain the quality of randomized controlled trials (RCTs) in diabetes.RESEARCH DESIGN AND METHODS -We identified the 10 most recently published trials as of 31 October 2003 in each of six general medical, five diabetes, and five metabolism and nutrition journals and further enriched our sample with 10 additional RCTs from each of five journals that published the most eligible RCTs in a year. We explored the association between trial characteristics and reporting quality using univariate analyses and a preplanned multivariate regression model. RESULTS-After excluding redundant reports of included trials and one trial that measured outcomes on the health system and not on patients, we included 199 RCTs: 119 assessed physiological and other laboratory outcomes, 42 assessed patient-important outcomes (e.g., morbidity and mortality, quality of life), and 38 assessed surrogate outcomes (e.g., disease progression or regression, HbA 1c , cholesterol). Fifty-three percent were of low methodological quality, as were one-third (36 -40%) of trials reporting patient-important or surrogate outcomes and two-thirds (64%) of laboratory investigations. Independent predictors of low quality were nonprofit funding source (odds ratio 3.1 [95% CI 1. CONCLUSIONS -There is ample room for improving the quality of diabetes trials. To enhance the practice of evidence-based diabetes care, trialists need to pay closer attention to the rigorous implementation and reporting of important methodological safeguards against bias in randomized trials. Diabetes Care 29:1833-1838, 2006A key principle of evidence-based practice is that one should seek to apply the best available evidence from clinical research (1,2). The expression "best available" suggests a hierarchy of evidence; one ought to draw stronger inferences from evidence that comes from high-quality studies with optimal safeguards to prevent random and systematic error (bias). Most hierarchies of evidence about interventions place high-quality randomized controlled trials (RCTs) at the top of the hierarchy (3). Following this principle, diabetes practitioners should pay particular attention to RCTs to guide their practice.Not all RCTs share the same quality; that is, not all RCTs yield unbiased results. In the laboratory clinical investigation tradition, "quality" has referred almost exclusively to the rigorousness and reproducibility of the experimental procedures performed on the volunteers as well as the precise and accurate nature of the laboratory determinations. In conducting systematic reviews of RCTs in diabetes (4 -6), we have noticed that investigators seem to pay little attention (as judged by the extent to which they report these methods) to methodological safeguards that limit the introduction of bias into RCTs. As a result, these potentially biased RCTs could mislead clinicians. Readers only have access to the methods as reported. When reports leave out critical information about methodol...