Critical appraisal (I): Fundamentals, tools, and application to scientific articles on outcomes and harmful effects

Evidence-Based Medicine relies on five structured steps: formulating a question, searching for evidence, critical appraisal of the evidence, assessing applicability and evaluating performance. While all steps are essential, critical appraisal is the central component, implemented in three stages: analyzing validity or scientific rigor (including both internal and external validity), evaluating clinical relevance or importance (considering quantitative, qualitative, comparative dimensions, and the balance of benefits, risks, and costs), and determining applicability (in routine clinical practice). Among the useful tools for critical appraisal, notable resources include templates and materials from CASPe and Osteba, as well as the epidemiological calculator Calcupedev, developed by the Committee on Evidence-Based Pediatrics. This article explores the necessary process of critically appraising studies on prognostic and risk factors through the analysis of observational studies (cohort and case-control studies).