Clinical practice guidelines sometimes make conflicting recommendations.1 2 3 4 5 6 7 8 For example, a sore throat may be managed differently in North America, France, and Finland—where guidelines recommend that a diagnostic test should be performed and that treatment should be conditional on its result—than it would be in England, Scotland, the Netherlands, and Belgium—where guidelines recommend that the decision to prescribe penicillin should depend mainly on the severity of symptoms, with no testing.1

Such disagreements occur for both valid and non-valid reasons. Valid reasons include honest differences in the many judgments that go into a recommendation—judgments about which research is relevant; the risk of bias in that research; the applicability of the research findings to the question at hand; and the relative importance of the anticipated benefits, adverse effects, and costs. Non-valid reasons include conflicts of interest, lack of awareness of relevant evidence or ignoring such evidence, failure to appraise the relevant research critically, failure to consider outcomes that are important …