title: Accuracy and cost of diagnostic strategies for patients with suspected Crohn's disease.
abstract: OBJECTIVE
  To evaluate accuracy and cost of non-invasive diagnostic strategies including magnetic resonance imaging, intestinal ultrasonography, ileocolonoscopy and video-capsule endoscopy in suspected Crohn's disease.
  
  
  METHODS
  A decision-analytic model was used to assess the costs in low (25%), intermediate (50%) or high (75%) pre-test probability of Crohn's disease. Based on the published accuracy of diagnostic modalities and Bayes' rule, we calculated post-test probability of Crohn's disease using different strategies, starting from ileocolonoscopy, ultrasonography or magnetic resonance. Each strategy was considered successful when post-test probability was >95% or <5%.
  
  
  RESULTS
  With low pre-test probability, only ileocolonoscopy as the first investigation could exclude or confirm Crohn's disease while a normal ultrasonography may exclude Crohn's disease. With high pre-test probability, ileocolonoscopy or ultrasonography as the first test may confirm Crohn's disease, but at least 3 negative tests are required to exclude Crohn's disease. The cost to diagnose one patient was cheapest utilising an ultrasonography-based strategy both in low (ultrasonography €1076; ileocolonoscopy €2005; magnetic resonance €4515) and high pre-test probability of Crohn's disease (ultrasonography €321; ileocolonoscopy €712; magnetic resonance €1412).
  
  
  CONCLUSIONS
  The accuracy and cost of these strategies depend on pre-test probability of Crohn's disease and vary according to the first test used. Ileocolonoscopy plus ultrasonography is the most accurate and less expensive initial diagnostic strategy.
authors.affiliation: Gastroenterology Unit, Department of Biomedical and Clinical Sciences, L. Sacco University Hospital, Milan, Italy. Electronic address: giovanni.maconi@unimi.it.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Maconi
authors.affiliation: Department of Decision Sciences, Bocconi University, Milan, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Bolzoni
authors.affiliation: Department of Decision Sciences, Bocconi University, Milan, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Giussani
authors.affiliation: Department of Gastroenterology, The Alfred Hospital and Monash University, Melbourne, Victoria, Australia.
authors.forename: Antony B
authors.initials: AB
authors.lastname: Friedman
authors.affiliation: Medical Statistics and Biometry Unit, Department of Biomedical and Clinical Sciences, L. Sacco University Hospital, Milan, Italy.
authors.forename: Piergiorgio
authors.initials: P
authors.lastname: Duca
mesh_terms: D003424:Crohn Disease / Q000175:diagnosis*; D003661:Decision Support Techniques; D016099:Endoscopy, Gastrointestinal / Q000191:economics; D006801:Humans; D007422:Intestines / Q000000981:diagnostic imaging / Q000473:pathology; D007558:Italy; D008279:Magnetic Resonance Imaging / Q000191:economics; D012680:Sensitivity and Specificity; D014463:Ultrasonography / Q000191:economics
keywords: Crohn's disease; Diagnostic strategy; Ileocolonoscopy; Magnetic resonance imaging; Ultrasound; Video capsule endoscopy