title: A theoretical framework for measuring knowledge in screening decision aid trials.
abstract: OBJECTIVE
  To describe a theoretical framework for assessing knowledge about the possible outcomes of participating in bowel cancer screening for the faecal occult blood test.
  
  
  METHODS
  The content of the knowledge measure was based on the UK General Medical Council's screening guidelines and a theory-based approach to assessing gist knowledge (Fuzzy Trace Theory). It comprised conceptual and numeric questions to assess knowledge of the underlying construct (e.g. false positive concept) and the approximate numbers affected (e.g. likelihood of a false positive). The measure was used in a randomised controlled trial involving 530 adults with low education, to compare the impact of a bowel screening decision aid with a screening information booklet developed for the Australian Government National Bowel Cancer Screening Program.
  
  
  RESULTS
  The numeric knowledge scale was particularly responsive to the effects of the decision aid; at follow-up decision aid participants' numeric knowledge was significantly greater than the controls (P<0.001). This contrasts with the conceptual knowledge scale which improved significantly in both groups from baseline to follow-up (P<0.001).
  
  
  CONCLUSIONS
  Our theory-based knowledge measure was responsive to change in conceptual knowledge and to the effect on numeric knowledge of a decision aid.
  
  
  CONCLUSIONS
  This theoretical framework has the potential to guide the development of knowledge measures in other screening settings.
authors.affiliation: Psychosocial Research Group, Prince of Wales Clinical School, University of New South Wales, Sydney, NSW, Australia. sian.smith@unsw.edu.au
authors.forename: Sian K
authors.initials: SK
authors.lastname: Smith
authors.forename: Alexandra
authors.initials: A
authors.lastname: Barratt
authors.forename: Lyndal
authors.initials: L
authors.lastname: Trevena
authors.forename: Judy M
authors.initials: JM
authors.lastname: Simpson
authors.forename: Jesse
authors.initials: J
authors.lastname: Jansen
authors.forename: Kirsten J
authors.initials: KJ
authors.lastname: McCaffery
mesh_terms: D000328:Adult; D001315:Australia; D002755:Choice Behavior; D003657:Decision Making; D003661:Decision Support Techniques; D004522:Educational Status; D036262:Empirical Research; D005243:Feces; D005500:Follow-Up Studies; D017143:Fuzzy Logic; D007722:Health Knowledge, Attitudes, Practice; D006801:Humans; D007258:Informed Consent; D007414:Intestinal Neoplasms / Q000175:diagnosis* / Q000517:prevention & control; D008297:Male; D008403:Mass Screening; D009780:Occult Blood; D010174:Pamphlets; D010342:Patient Acceptance of Health Care; D010353:Patient Education as Topic / Q000379:methods*; D010358:Patient Participation