title: Therapeutic decisions by number needed to treat and survival gains: a cross-sectional survey of lipid-lowering drug recommendations.
abstract: BACKGROUND
  Previous studies suggest that lay people have difficulties with evaluating effect size in terms of number needed to treat (NNT), but they are sensitive to effect size in terms of survival gains.
  
  
  OBJECTIVE
  To explore whether GPs and internists are sensitive to NNT and survival gains when considering a lipid-lowering drug therapy.
  
  
  METHODS
  Cross-sectional survey of primary prevention of cardiovascular disease with random allocation to different scenarios.
  
  
  METHODS
  GPs (n = 450) and internists (n = 450) were posted a vignette presenting a high-risk patient and a novel drug, 'neostatin'. The benefit was described in terms of NNT or mean gain in disease-free survival. Each physician was randomly allocated to one version of the vignette. Outcome measures were evaluation of 'neostatin' on a Likert scale (0: very poor choice, 10: very good choice) and the proportion recommending 'neostatin'.
  
  
  RESULTS
  A total of 477 responses (53%) were received. Among responders to NNT scenarios, 26%, 31%, and 43% recommended 'neostatin' for NNT values of 34, 17, and 9 respectively. With equivalent disease-free survival gains of 9, 17, and 32 months, 40%, 49%, and 52% respectively recommended the drug. On the rating scale, mean values were 4.7, 5.0, and 5.5 across the respective NNT scenarios and 5.2, 6.2, and 6.1 across the scenarios presenting survival gains. Differences in trends between the two formats were not statistically significant. In total, 33% recommended 'neostatin' when presented with NNT values, compared to 47% when presented with survival gain (χ(2) = 9.2, P= 0.002).
  
  
  CONCLUSIONS
  Physicians presented with survival gains were more likely to recommend the therapy than those presented with NNT. Sensitivity to effect size was similar for both effect formats.
authors.affiliation: National Centre of Rural Medicine, Institute of Community Medicine, University of Tromsø, Tromsø, Norway. peder.halvorsen@kraftlaget.no
authors.forename: Peder A
authors.initials: PA
authors.lastname: Halvorsen
authors.forename: Torbjørn F
authors.initials: TF
authors.lastname: Wisløff
authors.forename: Henrik
authors.initials: H
authors.lastname: Støvring
authors.forename: Olaf
authors.initials: O
authors.lastname: Aasland
authors.forename: Ivar Sønbø
authors.initials: IS
authors.lastname: Kristiansen
mesh_terms: D002318:Cardiovascular Diseases / Q000517:prevention & control*; D003430:Cross-Sectional Studies; D003657:Decision Making; D005194:Family Practice; D005260:Female; D006801:Humans; D000960:Hypolipidemic Agents / Q000627:therapeutic use*; D007396:Internship and Residency; D008297:Male; D008875:Middle Aged; D009664:Norway; D010818:Practice Patterns, Physicians'; D018401:Sample Size; D016019:Survival Analysis
chemical_list: D000960:Hypolipidemic Agents