Choosing wisely between randomized controlled trials and observational designs in studies about interventions.

Abstract

1. Divisao de Pneumologia, Instituto do Coracao – InCor – Hospital das Clinicas, Faculdade de Medicina, Universidade de Sao Paulo (SP) Brasil. 2. Methods in Epidemiologic, Clinical and Operations Research–MECOR–program, American Thoracic Society/Asociacion Latinoamericana del Torax. 3. Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles (CA) USA. Randomized controlled trials (RCTs) are the gold standard for evaluating the efficacy of interventions, because they avoid key sources of bias by randomly allocating participants to the treatment or control. That feature of the study design makes RCTs the highest ranked type of study within the Evidence-Based Medicine framework grading system. However, not all questions about health interventions can be answered with an RCT. Observational studies may be more appropriate to study certain aspects about interventions and thus complement RCTs.