The intellectual infrastructures of evidence-based medicine (EBM) are the levels of evidence and the grades of recommendation for the following types of research articles: therapy/prevention, etiology/harm, prognosis, diagnosis, differential diagnosis/symptom prevalence study, economic analysis/decision analysis. The levels of evidence for therapy (1 to 5) progress from systematic reviews (with homogeneity) of randomized control trials (RCT) of high quality, level 1, to level 5-expert opinion without explicit critical appraisal, or based on physiology, bench research, or "first principles." The grades of recommendation (A, B, C, D) are founded on the quality of the evidence defined by its level. These grades are aimed at helping clinicians understand the source from whence came statements in, for example, guidelines. The development of surgical procedures and their introduction into practice has not depended upon the RCT but rather upon an enthusiast performing a case series, sometimes with clearly defined results. Should all operations and procedures be evaluated by an RCT? Clearly not, and the levels of evidence support this quite clearly with the "all or none" research category as level 1c. This relates to frequent clinical situations requiring a solution often immediate, eg, pus, a ruptured aneurysm, a sucking chest wound, that do not lend themselves to a trial, as the control regimen (doing nothing) would lead to death. Techniques evolve with experience usually based on an understanding of pathophysiology. At what point should an RCT enter into the resolution of surgical therapies? Can observational studies correctly designed and carried out do the job? Two new study classifications have been introduced: in level 1, category c "all or none" studies; and in level 2, category c "outcomes" research. In neither is there much definition. Are these the areas into which the evaluation of new surgical procedures and technology should be placed? The surgical community is faced with dramatic changes in technology and evolving techniques, and needs to define the rules of evidence applicable to their discipline with the same rigor that the EBM gurus have used, in order for surgeons to define evidence-based surgical practice. (C) 2002 Excerpta Medica. Inc. All rights reserved.
