Chapter 15 – Systematic Reviews of Nonrandomized Studies of Interventions

Jelena Savović, Penny F. Whiting, Olaf M. Dekkers

Abstract

Systematic reviews of randomized controlled trials (RCTs) are considered the gold standard evidence for health care interventions. Nevertheless, nonrandomized studies of interventions (NRSIs) are often necessary to answer research questions about long-term or rare (adverse) outcomes or to evaluate interventions for which RCTs are unavailable. Review methods for NRSIs are broadly similar to those for reviews of RCTs. Assessing risk of bias is a particularly important step for NSRIs, because NRSIs have an inherently greater risk of bias than RCTs. NRSIs may be available in a variety of different designs, each with their own strengths and weaknesses. The decision on whether to combine estimates from NRSIs statistically should be guided by the similarity of populations, interventions, and outcomes in included studies, and informed by the risk of bias assessment. If such a synthesis is conducted, careful consideration and exploration of differences in study characteristics and statistical heterogeneity are essential.

Corrections

There are currently no corrections for this chapter.

Resources

There are currently no resources for this chapter.

Practicals

There are no practicals for this chapter.

Author affiliations

Jelena Savović

Population Health Sciences, Bristol Medical School, University of Bristol, Bristol, UK
National Institute of Health Research Applied Research Collaboration West, University Hospitals Bristol and Weston NHS Foundation Trust, Bristol, UK

Penny F. Whiting

Population Health Sciences, Bristol Medical School, University of Bristol, Bristol, UK

Olaf M. Dekkers

Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark
Department of Clinical Epidemiology, Leiden University Medical Centre, Leiden, The Netherlands

How to cite this chapter?

For the printed version of the book

Savović, J., Whiting, P.F. and Dekkers, O.M. (2022). Chapter 15. Systematic reviews of nonrandomized studies of interventions. In: Systematic Reviews in Health Research: Meta-analysis in Context (eds M. Egger, J.P.T. Higgins and G. Davey Smith), pp 271-295. Hoboken, NJ : Wiley.