Evidence-Based Medicine and Practice Guidelines - An Overview

Steven H.Woolf, MD, MPH, Department of Family Practice, Medical College of Virginia - Virginia Commonwealth University, Fairfax, Virginia.

Cancer Control. 2000;7(4) 

In This Article

Distinguishing Features of EBM

Seasoned clinicians sometimes question the novelty of EBM, noting that medicine has always been "evidence-based." Indeed, since the times of Ancient Greece, physicians have engaged in scientific study and have tried to keep abreast of the latest evidence. What distinguishes EBM from the traditional application of evidence in medicine, however, is the explicit linkage between policy and supporting data.

EBM emphasizes an examination of the evidence that is comprehensive, critical, and explicit. Comprehensiveness is important to ensure that all evidence is considered rather than just those studies that support a particular viewpoint or that reflect a selection bias. Critical appraisal is emphasized to examine the strengths and weakness of the study designs so that judgments about the evidence can be linked to quality. Explicitness gives transparency to the evaluation, allowing readers to understand the methods used in the analysis, the strengths of the evidence, the gaps that exist, and the rationale for practice recommendations or policies, whether evidence-or opinion-based.

Misconceptions about EBM abound. [6] Chief among these is the presumption that EBM resists any medical practice that has not been proven in a RCT or other study. Many believe that EBM seeks to convert clinical practice into "cookbook medicine," impeding efforts by clinicians to exercise clinical judgment and individualize care. Although this occurs, sometimes under the false guise of EBM, it is neither advocated by EBM nor defensible on rational grounds. Very little of what is done in clinical practice has been tested in controlled studies. It would therefore be unrealistic and invalid to withhold services based on this criterion. Studies such as RCTs are difficult to design and fund, often require years of follow-up to achieve results, and rely on outcome measures that may not capture the range of benefits and harms associated with interventions. [7,8]

Evidence that is available is often of poor quality, either in terms of internal validity (the extent to which the data are reflective of the clinical setting in which the study was conducted) or external validity (the extent to which the findings can be extrapolated to other patient populations, providers, or settings). Even the best evidence can provide only "averages" for predicting outcomes in a given patient. Individual variables (eg, risk factors, past medical history, personal circumstances, provider skills, community resources) influence where a patient will fall in the bell curve that surrounds the mean.

EBM does not gloss over these considerations but insists on making them explicit. It does not insist on evidence from RCTs but does demand that the grade and quality of the evidence be carefully evaluated and stated clearly. EBM does not preclude the use of opinion or expert judgment in setting practice policy but does insist on acknowledging when this is done. It advocates disclosure of gaps in the evidence to help clarify research agendas and calls attention to design features that future studies should incorporate to address deficiencies in current data. Finally, EBM does not mask over the importance of individualized care. It encourages that the determinant factors in practice and policy decisions be evidence-based to maximize equity and effectiveness for all patients.