Evidence‐based medicine—When observational studies are better than randomized controlled trials

Nephrology, vol. 25, pp. 737–743

Abstract

In evidence-based medicine, clinical research questions may be addressed by different study designs. This article describes when randomized controlled trials (RCT) are needed and when observational studies are more suitable. According to the Centre for Evidence-Based Medicine, study designs can be divided into analytic and non-analytic (descriptive) study designs. Analytic studies aim to quantify the association of an intervention (eg, treatment) or a naturally occurring exposure with an outcome. They can be subdivided into experimental (ie, RCT) and observational studies. The RCT is the best study design to evaluate the intended effect of an intervention, because the randomization procedure breaks the link between the allocation of the intervention and patient prognosis. If the randomization of the intervention or exposure is not possible, one needs to depend on observational analytic studies, but these studies usually suffer from bias and confounding. If the study focuses on unintended effects of interventions (ie, effects of an intervention that are not intended or foreseen), observational analytic studies are the most suitable study designs, provided that there is no link between the allocation of the intervention and the unintended effect. Furthermore, non-analytic studies (ie, descriptive studies) also rely on observational study designs. In summary, RCTs and observational study designs are inherently different, and depending on the study aim, they each have their own strengths and weaknesses.

Authors 7

1. Jizzo R. Bosdriesz

   Amsterdam UMC Location University of Amsterdam · Amsterdam Public Health · Amsterdam University Medical Centers · University of Amsterdam

   Affiliation as printed

   ERA‐EDTA Registry, Department of Medical Informatics Amsterdam Public Health Research Institute, Amsterdam UMC‐location AMC, University of Amsterdam Amsterdam The Netherlands

   ERA-EDTA Registry, Department of Medical Informatics, Amsterdam Public Health Research Institute, Amsterdam UMC-location AMC, University of Amsterdam, Amsterdam, The Netherlands

2. Vianda S Stel corresponding

   Amsterdam UMC Location University of Amsterdam · Amsterdam Public Health · Amsterdam University Medical Centers · University of Amsterdam

   Affiliation as printed

   ERA‐EDTA Registry, Department of Medical Informatics Amsterdam Public Health Research Institute, Amsterdam UMC‐location AMC, University of Amsterdam Amsterdam The Netherlands

   ERA-EDTA Registry, Department of Medical Informatics, Amsterdam Public Health Research Institute, Amsterdam UMC-location AMC, University of Amsterdam, Amsterdam, The Netherlands

3. Merel van Diepen Aachen Department of Clinical Epidemiology Leiden University Medical Center Leiden The Netherlands Department of Clinical Epidemiology

   Leiden University Medical Center

   Affiliation as printed

   Department of Clinical Epidemiology Leiden University Medical Center Leiden The Netherlands

   Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, The Netherlands

4. Yvette Meuleman Aachen Department of Clinical Epidemiology Leiden University Medical Center Leiden The Netherlands Department of Clinical Epidemiology

   Leiden University Medical Center

   Affiliation as printed

   Department of Clinical Epidemiology Leiden University Medical Center Leiden The Netherlands

   Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, The Netherlands

5. Friedo Wilhelm Dekker Aachen Department of Clinical Epidemiology Leiden University Medical Center Leiden The Netherlands Department of Clinical Epidemiology

   Leiden University Medical Center

   Affiliation as printed

   Department of Clinical Epidemiology Leiden University Medical Center Leiden The Netherlands

   Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, The Netherlands

6. Carmine Zoccali
   Affiliation as printed

   CNR‐IFC Clinical Epidemiology and Pathophysiology of Renal Diseases and Hypertension Reggio Calabria Italy

   CNR-IFC, Clinical Epidemiology and Pathophysiology of Renal Diseases and Hypertension, Reggio Calabria, Italy

7. Kitty J. Jager

   Amsterdam UMC Location University of Amsterdam · Amsterdam Public Health · Amsterdam University Medical Centers · University of Amsterdam

   Affiliation as printed

   ERA‐EDTA Registry, Department of Medical Informatics Amsterdam Public Health Research Institute, Amsterdam UMC‐location AMC, University of Amsterdam Amsterdam The Netherlands

   ERA-EDTA Registry, Department of Medical Informatics, Amsterdam Public Health Research Institute, Amsterdam UMC-location AMC, University of Amsterdam, Amsterdam, The Netherlands