A practitioner's guide to developing critical appraisal skills: How to interpret the magnitude of clinical study results

Abstract

Background: In the oral health literature, researchers sometimes report measures of association that are inappropriate for their study design. Clinicians using evidence to inform their practice should be able to interpret clinical study results on the basis of the types of measures of association, independent of what the researchers of a study reported.

Types of studies reviewed: The authors summarized which measures of association can be derived from experimental and observational studies and how to interpret them in the context of different study designs. They also suggested how inferences can be made on the basis of particular designs.

Results: Measures of association derived from randomized controlled trials and cohort studies differ from those of case-control and cross-sectional studies. These differences can be attributed to the temporality between exposures and outcomes inherent in the respective study designs. Different measures of association reported from the same study may lead to different clinical decisions. Furthermore, the same measure of association with the same effect estimate derived from different study designs may contribute to different clinical decisions.

Conclusions and practical implications: Measures of association should be interpreted in the context of a particular study design. Study designs and specific measures of association should be considered when drawing conclusions from clinical studies. Clinicians using the literature to inform practice should be cognizant of measures of association reported for a particular study design and whether the authors have interpreted the measure of association correctly in the context of their chosen study design.

Keywords: Measure of association; absolute risk difference; contingency table; odds ratio; relative risk; relative risk difference; study design.