A guideline’s formulation should include a clear question with specification of all outcomes of importance to patients GRADE offers four levels of evidence quality: high, moderate, low, and very low Randomised trials begin as high quality evidence and observational studies as low quality evidence Quality may be downgraded as a result of limitations in study design or implementation, imprecision of estimates (wide confidence intervals), variability in results, indirectness of evidence, or publication bias Quality may be upgraded because of a very large magnitude of effect, a dose-response gradient, . . . [Full text of this article]