The GATE frame: critical appraisal with pictures (Editorial)

Abstract

Epidemiologic evidence about the accuracy of diagnostic tests, the power of prognostic markers, and the efficacy and safety of interventions is the cornerstone of evidence-based health care ( 1). Practitioners of evidence-based health care require critical appraisal skills to judge the validity of this evidence. The members of the Evidence-Based Medicine (EBM) Working Group are international leaders in teaching critical appraisal skills, and their users' guides for appraising the validity of the health care literature ( 2) have long been the basis of teaching programs worldwide. However, we found that many of our students took a reductionist "paint by numbers" approach when using the Working Group's guides. Students could answer individual appraisal questions correctly but had difficulty assessing overall study quality. We believed that to be due to a poor understanding of epidemiologic study design. So, over the past 15 years of teaching critical appraisal we have modified the McMaster approach and developed the Graphic Appraisal Tool for Epidemiological studies (GATE) frame to help our students conceptualize the whole study as well as its components. GATE is a visual framework that illustrates the generic design of all epidemiologic studies (Figure 1). We now teach critical appraisal by "hanging" studies and the EBM Working Group's appraisal questions on the GATE frame. This editorial outlines the GATE approach to critical appraisal, illustrated throughout using the Heart and Estrogen/progestin Replacement Study (HERS), a randomized, double-blind, placebo-controlled trial of the effect of daily estrogen plus progestin on coronary heart disease (CHD) death in postmenopausal women ( 3). A detailed critical appraisal of HERS using a GATE-based checklist is available online ( 4).