临床指南应用的相关因素 Relevance x Validity Usefulness= Work Usefulness: 指南的实用性 Relevance: 与具体病人相符合的程度 Validity: 文献的真实性、科学性 Work: 获得证据所花的时间、精力和难易程度 Figure.Usefulness equation.Slawson DC,Becoming a medical information master: feeling good about not knowing everything.J Fam Pract 1994;38:505-13