It is traditionally held that the first comparative clinical trial was performed in 1747 by Dr. James Lind (1716-1794) of the British Royal Navy to identify a treatment for scurvy. Lind evenly assigned 12 scurvy-afflicted sailors aboard the HMS Salisbury to receive cider, vitriol (a weak acid), vinegar, seawater, oranges and lemons, or nutmeg paste. After 6 days, only the two sailors who had received oranges and lemons (and thus adequate amounts of vitamin C) had sufficiently recovered to return to duty. Two centuries later, the advent of the pharmaceutical industry and the evolution of methodological concepts led to the first controlled clinical trial in which patients were randomly assigned to different treatments. Performed in 1947-1948, it observed the effects of streptomycin on pulmonary tuberculosis to be significantly better than those of a placebo.
Evidence-Based Medicine
In contrast, common acceptance of the merit of individual medical or surgical practice—the proverbial “in my experience” (N of one), “in case after case, I have seen” (N of two), and “in my series” (N of three)—evidence-based medicine (EBM) acknowledges that simple intuition, unsystematic clinical experience, and a pathophysiologic rationale are inadequate bases for clinical decision making. EBM stresses the critical examination of evidence from clinical research. EBM likewise offers a formal set of steps to complement medical training and “common sense” for clinicians to effectively interpret the results of clinical research (“how to read a paper”) and apply them in their practice ( Box 80.1 ). Last, EBM places a lower value on expert authority than the traditional medical paradigm.
- 1.
Asking focused questions: Translation of uncertainty to an answerable question.
- 2.
Finding the evidence: Systematic retrieval of best evidence available.
- 3.
Critical appraisal: Testing evidence for validity, clinical relevance, and applicability.
- 4.
Making a decision: Application of results in practice.
- 5.
Evaluating performance: Auditing evidence-based decisions.
Many systems for grading the level or quality of evidence and the strength of recommendations have been created. Unfortunately, guideline developers around the world are inconsistent in how they rate quality of evidence and grade strength of recommendations—resulting in confusion among guideline users. Although the Grading of Recommendations Assessment, Development and Evaluation (GRADE) Working Group is not without limitations, it defines and clearly delineates all of the major domains that affect the reliability of research evidence, including the quantity, quality, consistency, and types of studies of the published evidence, resulting in one of three grades of evidence (high, moderate, or low). GRADE also assigns a rating for strength of evidence of strong or weak, based on the estimate of net benefit relative to harms and other factors, including the quality of evidence, importance of patient preferences and values, as well as costs and burdens. Each recommendation is thus assigned one of six possible grades, based on the strength of the recommendation and the quality of evidence ( Table 80.1 ). Many groups—including the Cochrane Collaboration, the American College of Physicians (ACP), the American College of Chest Physicians (ACCP), the U.S. Agency for Healthcare Research and Quality (AHRQ), the UK National Institute for Health and Clinical Excellence (NICE), and the World Health Organization (WHO)—have adopted GRADE.
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