title: The 'number need to treat': does it help clinical decision making?
abstract: The number needed to treat (NNT) is an increasingly popular way of presenting the effects of treatment. However, the NNT varies markedly depending on the baseline risk of patients, the outcome considered, and the clinical setting. Furthermore geographic and secular trends make the NNT unstable between places and over time. Particular caution is needed in deriving the NNT from pooled absolute risk differences in meta-analysis. In general, the NNT should be calculated by applying the relative risk reduction on treatment estimated by trials or meta-analysis to populations of specified absolute high, average or low risk to illustrate a range of possible NNTs.
authors.affiliation: Department of Social Medicine, University of Bristol, Canynge Hall, Whiteladies Road, Bristol BS8 2PR, UK.
authors.forename: S
authors.initials: S
authors.lastname: Ebrahim
authors.forename: G D
authors.initials: GD
authors.lastname: Smith
mesh_terms: D000959:Antihypertensive Agents / Q000627:therapeutic use*; D003657:Decision Making; D006801:Humans; D006973:Hypertension / Q000188:drug therapy*; D015201:Meta-Analysis as Topic; D017063:Outcome Assessment, Health Care; D010560:Personnel Selection; D016032:Randomized Controlled Trials as Topic
chemical_list: D000959:Antihypertensive Agents