Evidence hierarchies reflect the relative authority of various types of biomedical research. Although there is no single, universally-accepted hierarchy of evidence,^[1] there is broad agreement on the relative strength of the principal types of research. Randomized controlled trials (RCTs) rank above observational studies, while expert opinion and anecdotal experience are ranked at the bottom. Some evidence hierarchies place systematic review and meta analysis above RCTs, since these often combine data from multiple RCTs, and possibly from other study types as well. Evidence hierarchies are integral to evidence-based medicine.

The use of evidence hierarchies has been criticized as allowing RCTs too much authority. Not all research questions can be answered through RCTs, either because of practical issues or because of ethical issues. Moreover, even when evidence is available from high-quality RCTs, evidence from other study types may still be relevant.

References

1. ↑ Two examples of evidence hierarchies can be found in the qualification of evidence section of the Wikipedia article on evidence-based medicine.

External links

School of Health and Related Research, University of Sheffield, "Hierarchy of evidence". http://www.shef.ac.uk/scharr/ir/units/systrev/hierarchy.htm. Accessed 2008-03-31.