Searching the biomedical literature: research study designs and critical appraisal.

Two essential issues to consider when assessing the validity of research studies are the strengths and weaknesses of the study design and quality of methodology. This paper reviews study designs commonly used in clinical research, including case reports, cross-sectional studies, case-control studies, cohort studies, randomized controlled trials, reviews, and meta-analyses. It concludes with an outline for assessing study quality.