Evaluating the evidence: an introduction

Health care has always sought to improve the health of patients, but our interventions do not always do more good than harm. Sometimes ineffective or harmful interventions are used and effective interventions are not used. A key problem has been that decisions are too often based on inadequate evidence or that sound evidence is overlooked. Basing decisions on evidence involves three steps: finding evidence relating to the decision, evaluating it, and acting on it. Evaluating evidence in turn involves assessing its validity, understanding the findings and their implications, and understanding the relevance of the results in the context of local decision‐making. Developing evidence‐based health care is a collective enterprise which, while not easy, is something to which everyone in the health service can contribute.