Evidence-based management of patients with osteoporosis.
Evidence-based medicine (EBM) offers an approach to solving clinical problems that places a high value on systematic clinical investigation. Evidence-based clinicians look to the highest rung on a hierarchy of evidence to guide their patient management. When considering therapeutic decisions, randomized control trials examining impact on outcomes that patients feel are important are at the top of the hierarchy of individual studies. Systematic reviews of such trials provide the best evidence for patient care decisions. Systematic reviews include explicit eligibility criteria for studies they include, a comprehensive search, an explicit rating of the methodological quality of the individual trials, and explicit strategies for pooling data. Inferences are weakened if study design is weak (trials are not blinded or we have only observational studies on which to rely), if results are inconsistent across studies, or if studies rely on substitute end points (bone density rather than long-bone fractures). Evidence-based clinicians consider not only the strength of evidence, but the patients' risk of adverse target outcomes and the magnitude of treatment effects in making their therapeutic decisions. EBM encourages quantitative approaches to trading off benefits and risks. For example, in deciding whether to recommend hormone replacement therapy to a 50-yr-old, an evidence-based clinician would consider that the woman has a 15% lifetime risk of fracturing her hip and the median age of the fracture is 79. Observational studies suggest that long-term estrogen therapy will reduce this risk by 25%, and we must therefore treat 25 women for 30 yr to prevent a single fracture. Evidence-based clinicians are also aware that evidence never provides an adequate guide for treatment decisions when considered on its own. Each therapeutic decision involves a trade-off between benefits and risks, and value judgments are invariably involved in making that trade-off.
McMaster University, Hamilton, Ontario. guyatt@mcmaster.ca
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