title: Types of clinical studies. I. Case-control studies.
abstract: In an age when there is a general belief that clinical practice should be based on the best scientific evidence available, its selection and critical appraisal is crucial. The first step should therefore be to define the existing types of studies, and analyze their objectives, advantages and disadvantages, use and synthesis. In this, the first of a series of articles defining types of clinical studies, we present case-control studies. This type of study is a valid research methodology, producing important data with less time, cost and effort than other types of research studies. Its implementation, however, is complicated by the fact that case-control studies are more susceptible to bias. Attention to specific details--selection criteria for cases and controls, origin of the controls, blinding of data collectors and standardization of their procedures, and management of confounding factors--will improve the quality of the results obtained in case-control studies.
authors.affiliation: Centro de Estudos de Medicina Baseada na Evidência, Faculdade de Medicina de Lisboa, Lisboa, Portugal. avc@netcabo.pt
authors.forename: António Vaz
authors.initials: AV
authors.lastname: Carneiro
mesh_terms: D016022:Case-Control Studies; D004194:Disease / Q000209:etiology; D019317:Evidence-Based Medicine