Chapter 2: What Is Evidence-Based Medicine?

Introduction

Evidence-based medicine (EBM) involves conscientiously working with patients to help them resolve (sometimes) or cope with (often) problems related to their physical, mental, and social health. The EBM approach necessitates awareness and understanding of clinical research evidence. For those involved in making health care decisions, EBM encompasses creating implementation strategies to ensure practice evidence that is well grounded in best evidence research summaries.

At the core of EBM is a care and respect for patients who will suffer if clinicians fall prey to muddled clinical reasoning and to neglect or misunderstanding of research findings. Practitioners of EBM strive for a clear and comprehensive understanding of the evidence underlying their clinical care and work with each patient to ensure that chosen courses of action are in that patient's best interest. Practicing EBM requires clinicians to understand how uncertainty about clinical research evidence intersects with an individual patient's predicament and preferences. In this chapter, we outline how EBM proposes to achieve these goals and, in so doing, define the nature of EBM.

Three Fundamental Principles of EBM

Conceptually, EBM involves 3 fundamental principles. First, optimal clinical decision making requires awareness of the best available evidence, which ideally will come from systematic summaries of that evidence. Second, EBM provides guidance to decide whether evidence is more or less trustworthy—that is, how confident can we be of the properties of diagnostic tests, of our patients' prognosis, or of the impact of our therapeutic options? Third, evidence alone is never sufficient to make a clinical decision. Decision makers must always trade off the benefits and risks, burden, and costs associated with alternative management strategies and, in doing so, consider their patients' unique predicament and values and preferences.¹

Best Evidence Summaries

In 1992, Antman et al² published an article that compared the recommendations of experts for management of patients with myocardial infarction to the evidence that was available at the time the recommendations were made. Figures 2-1 and 2-2 summarize their results in forest plots. Both are cumulative meta-analyses: the first of thrombolytic therapy for myocardial infarction and the second for lidocaine antiarrhythmic therapy. In both cases, the line in the center represents an odds ratio of 1.0 (treatment is neither beneficial or harmful). As in any forest plot, the dots represent the best estimates of treatment effect (often from individual studies; in this case from the totality of accumulated evidence), and the associated lines represent the 95% confidence intervals (CIs).