RESUMO
OBJECTIVE: to characterize randomized controlled trials (RCTs) that did not report the overall number of participants assessed for eligibility and to identify factors associated with higher enrollment rates. STUDY DESIGN AND SETTING: Systematic review and meta-analysis of RCTs in several pre-defined fields in internal medicine. We randomly extracted 360 articles that were published in 2017. Trials that reported numbers of assessed for eligibility patients were compared with those who did not. Recruitment rates were calculated in order to investigate whether they were associated with trial characteristics. RESULTS: A total of 360 RCTs were included. Only 2-thirds of the trials (242/360) reported the number of patients assessed for eligibility. Trials reporting eligibility data had better methodology, reported on the tested hypothesis, included a placebo arm, evaluated soft outcomes, published their findings in higher impact journals and recruited a higher number of randomized patients than those who did not. Recruitment rates in 225 (62.5%) trials enabling their calculation, were significantly higher in trials sponsored by industry, conducted in multiple centers and countries, including inpatients, tested non-inferiority hypothesis, included a placebo arm, and evaluated surrogate outcomes. CONCLUSIONS: Reporting of participant eligibility continues to be scarce. Inadequate reporting was associated with poor methodological characteristics in trials.