title: Patients' expectations of screening and preventive treatments.
abstract: OBJECTIVE
  An informed decision to accept a health care intervention requires an understanding of its likely benefit. This study assessed participants' estimates of the benefit, as well as minimum acceptable benefit, of screening for breast and bowel cancer and medication to prevent hip fracture and cardiovascular disease.
  
  
  METHODS
  Three general practitioners sent questionnaires to all registered patients aged 50 to 70 years. Patients agreeing to participate in the study were asked to estimate the number of events (fractures or deaths) prevented in a group of 5,000 patients undergoing each intervention over a period of 10 years, and to indicate the minimum number of events avoided by the intervention that they considered justified its use. The proportions of participants that overestimated each intervention's benefit were calculated, and univariate and multivariable analyses of predictors of response were performed.
  
  
  RESULTS
  The participation rate was 36%: 977 patients were invited to participate in the study, and 354 returned a completed questionnaire. Participants overestimated the degree of benefit conferred by all interventions: 90% of participants overestimated the effect of breast cancer screening, 94% overestimated the effect of bowel cancer screening, 82% overestimated the effect of hip fracture preventive medication, and 69% overestimated the effect of preventive medication for cardiovascular disease. Estimates of minimum acceptable benefit were more conservative, but other than for cardiovascular disease mortality prevention, most respondents indicated a minimum benefit greater than these interventions achieve. A lower level of education was associated with higher estimates of minimum acceptable benefit for all interventions.
  
  
  CONCLUSIONS
  Patients overestimated the risk reduction achieved with 4 examples of screening and preventive medications. A lower level of education was associated with higher minimum benefit to justify intervention use. This tendency to overestimate benefits may affect patients' decisions to use such interventions, and practitioners should be aware of this tendency when discussing these interventions with patients.
authors.affiliation: Department of Public Health and General Practice, University of Otago, Christchurch, New Zealand. ben.hudson@otago.ac.nz
authors.forename: Ben
authors.initials: B
authors.lastname: Hudson
authors.forename: Abby
authors.initials: A
authors.lastname: Zarifeh
authors.forename: Lorraine
authors.initials: L
authors.lastname: Young
authors.forename: J Elisabeth
authors.initials: JE
authors.lastname: Wells
mesh_terms: D000368:Aged; D002318:Cardiovascular Diseases / Q000517:prevention & control*; D055088:Early Detection of Cancer / Q000379:methods*; D005260:Female; D006293:Health Promotion; D006620:Hip Fractures / Q000517:prevention & control*; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods*; D008875:Middle Aged; D017060:Patient Satisfaction; D011314:Preventive Health Services / Q000379:methods*; D040242:Risk Reduction Behavior; D011795:Surveys and Questionnaires