title: Implementation of a new CT colonography service: 5 year experience.
abstract: OBJECTIVE
  To describe our experience using a 5 year audit of computed tomography colonography (CTC) practice and identify factors that influence diagnostic performance to guide implementation in other centres.
  
  
  METHODS
  Consecutive patients referred for CTC at a single institution over a 5 year period were identified, and reporting rates and positive predictive value (PPV) calculated for small polyps, large polyps, and colorectal cancer. Diagnostic performance was compared using the Chi-squared test, and trends over time were examined with logistic regression. The effect of faecal tagging and an intravenous spasmolytic were investigated using Fisher's exact test.
  
  
  RESULTS
  In total, 4355 CTC examinations were performed. Overall reporting rates and PPV were 17% and 92%, respectively. Negative predictive value (NPV) for cancer was 99.9%. A significant decrease in reporting rate (p < 0.001) was accompanied by an increase in PPV for small polyps (p = 0.02) following the introduction of faecal tagging. Adequacy rates for CTC improved over time (96% to 99%), with improved adequacy rates when using a spasmolytic, 98% versus 96% without. A significant difference in reporting rates, but not PPV, was found between radiologists.
  
  
  CONCLUSIONS
  Accurate colonic investigation using CTC can be delivered safely to a high-risk patient population at a single centre. Faecal tagging and an intravenous spasmolytic improve diagnostic performance.
authors.affiliation: Intestinal Imaging Centre, St Mark's Hospital, Harrow, Middlesex, UK.
authors.forename: P F C
authors.initials: PF
authors.lastname: Lung
authors.affiliation: Intestinal Imaging Centre, St Mark's Hospital, Harrow, Middlesex, UK. Electronic address: burlingdavid@yahoo.co.uk.
authors.forename: D
authors.initials: D
authors.lastname: Burling
authors.affiliation: Intestinal Imaging Centre, St Mark's Hospital, Harrow, Middlesex, UK.
authors.forename: L
authors.initials: L
authors.lastname: Kallarackel
authors.affiliation: Intestinal Imaging Centre, St Mark's Hospital, Harrow, Middlesex, UK.
authors.forename: J
authors.initials: J
authors.lastname: Muckian
authors.affiliation: Intestinal Imaging Centre, St Mark's Hospital, Harrow, Middlesex, UK.
authors.forename: R
authors.initials: R
authors.lastname: Ilangovan
authors.affiliation: Intestinal Imaging Centre, St Mark's Hospital, Harrow, Middlesex, UK.
authors.forename: A
authors.initials: A
authors.lastname: Gupta
authors.affiliation: Intestinal Imaging Centre, St Mark's Hospital, Harrow, Middlesex, UK.
authors.forename: M
authors.initials: M
authors.lastname: Marshall
authors.affiliation: Intestinal Imaging Centre, St Mark's Hospital, Harrow, Middlesex, UK.
authors.forename: P
authors.initials: P
authors.lastname: Shorvon
authors.affiliation: Centre for Medical Imaging, UCL, London, UK.
authors.forename: S
authors.initials: S
authors.lastname: Halligan
authors.affiliation: Intestinal Imaging Centre, St Mark's Hospital, Harrow, Middlesex, UK.
authors.forename: G
authors.initials: G
authors.lastname: Bhatnagar
authors.affiliation: Intestinal Imaging Centre, St Mark's Hospital, Harrow, Middlesex, UK.
authors.forename: P
authors.initials: P
authors.lastname: Bassett
authors.affiliation: Centre for Medical Imaging, UCL, London, UK.
authors.forename: S A
authors.initials: SA
authors.lastname: Taylor
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000556:Ambulatory Surgical Procedures / Q000706:statistics & numerical data; D001071:Appointments and Schedules; D002400:Cathartics / Q000008:administration & dosage; D003111:Colonic Polyps / Q000000981:diagnostic imaging*; D023881:Colonography, Computed Tomographic / Q000706:statistics & numerical data*; D003113:Colonoscopy / Q000706:statistics & numerical data; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging*; D003287:Contrast Media / Q000008:administration & dosage; D003695:Delivery of Health Care / Q000706:statistics & numerical data; D005243:Feces / Q000737:chemistry; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D008485:Medical Audit; D008875:Middle Aged; D015588:Observer Variation; D010348:Patient Care Team; D011237:Predictive Value of Tests; D012017:Referral and Consultation / Q000706:statistics & numerical data; D006113:United Kingdom; D055815:Young Adult
chemical_list: D002400:Cathartics; D003287:Contrast Media