Urschel JD, Goldsmith CH, Tandan VR, Miller JD. Users’ guide to evidence-based surgery: how to use an article evaluating surgical interventions. Evidence-Based Surgery Working Group. Can J Surg 2001;44(2):95-100.


Surgeons have traditionally made therapeutic decisions based on existing surgical dogma, personal experience, recommendations of surgical authorities and thoughtful application of surgical basic sciences. Although this approach has served surgeons and their patients fairly well, ineffective or even harmful treatments can be erroneously accepted as the surgical treatment of choice. Evidence-based surgery emphasizes the need to evaluate properly the efficacy of diagnostic and therapeutic interventions before accepting them as standard surgical practice.

Evidence in clinical surgery varies in its quality, and this is reflected in several commonly used grading systems for medical evidence. Single case reports represent the lowest level of published evidence. They can be valuable as a stimulus for more formal research or as an important observation about a very rare condition. Retrospective case series are a common form of surgical publication. Comparisons of 2 or more therapies are often attempted in these studies, but the retrospective nature of data collection and difficulties comparing heterogeneous patient populations (often in different treatment eras) limit their usefulness. Prospective nonrandomized studies, such as comparisons of a concurrent cohort of patients, overcome some of the limitations of retrospective data collection and comparison to historical “controls.” However, they are prone to bias. Bias is defined as any factor or process that tends to deviate the results or conclusions of a trial systematically (not randomly) away from the truth. A properly designed and conducted randomized controlled trial provides a very high level of evidence on which to base surgical decisions. Finally, when several randomized controlled trials exist, a meta-analysis of these trials gives the highest level of evidence to support a specific form of treatment

Ideally, surgeons should critically examine published evidence and then adjust their practices accordingly. The purpose of this article is to assist surgeons with this process.

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