title: Using CT colonography as a triage technique after a positive faecal occult blood test in colorectal cancer screening.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the effectiveness of CT colonography (CTC) as a triage technique in faecal occult blood test (FOBT)-positive screening participants.
  
  
  METHODS
  Consecutive guaiac (G-FOBT) and immunochemical (I-FOBT) FOBT-positive patients scheduled for colonoscopy underwent CTC with iodine tagging bowel preparation. Each CTC was read independently by two experienced observers. Per patient sensitivity, specificity and positive and negative predictive values (PPV and NPV) were calculated based on double reading with different CTC cut-off lesion sizes using segmental unblinded colonoscopy as the reference standard. The acceptability of the technique to patients was evaluated with questionnaires.
  
  
  RESULTS
  302 FOBT-positive patients were included (54 G-FOBT and 248 I-FOBT). 22 FOBT-positive patients (7%) had a colorectal carcinoma and 211 (70%) had a lesion >or=6 mm. Participants considered colonoscopy more burdensome than CTC (p<0.05). Using a 6 mm CTC size cut-off, per patient sensitivity for CTC was 91% (95% CI 85% to 91%) and specificity was 69% (95% CI 60% to 89%) for the detection of colonoscopy lesions >or=6 mm. The PPV of CTC was 87% (95% CI 80% to 93%) and NPV 77% (95% CI 69% to 85%). Using CTC as a triage technique in 100 FOBT-positive patients would mean that colonoscopy could be prevented in 28 patients while missing >or=10 mm lesions in 2 patients.
  
  
  CONCLUSIONS
  CTC with limited bowel preparation has reasonable predictive values in an FOBT-positive population and a higher acceptability to patients than colonoscopy. However, due to the high prevalence of clinically relevant lesions in FOBT-positive patients, CTC is unlikely to be an efficient triage technique in a first round FOBT population screening programme.
authors.affiliation: Department of Radiology, Academic Medical Centre, Amsterdam, The Netherlands. M.H.Liedenbaum@amc.uva.nl
authors.forename: M H
authors.initials: MH
authors.lastname: Liedenbaum
authors.forename: A F
authors.initials: AF
authors.lastname: van Rijn
authors.forename: A H
authors.initials: AH
authors.lastname: de Vries
authors.forename: H M
authors.initials: HM
authors.lastname: Dekker
authors.forename: M
authors.initials: M
authors.lastname: Thomeer
authors.forename: C J
authors.initials: CJ
authors.lastname: van Marrewijk
authors.forename: L
authors.initials: L
authors.lastname: Hol
authors.forename: M G W
authors.initials: MG
authors.lastname: Dijkgraaf
authors.forename: P
authors.initials: P
authors.lastname: Fockens
authors.forename: P M M
authors.initials: PM
authors.lastname: Bossuyt
authors.forename: E
authors.initials: E
authors.lastname: Dekker
authors.forename: J
authors.initials: J
authors.lastname: Stoker
mesh_terms: D000236:Adenoma / Q000175:diagnosis* / Q000000981:diagnostic imaging; D000368:Aged; D002277:Carcinoma / Q000175:diagnosis / Q000000981:diagnostic imaging; D002400:Cathartics; D002755:Choice Behavior; D003111:Colonic Polyps / Q000175:diagnosis / Q000000981:diagnostic imaging; D023881:Colonography, Computed Tomographic; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging; D055088:Early Detection of Cancer; D005260:Female; D006801:Humans; D008067:Lipoma / Q000175:diagnosis / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D009780:Occult Blood; D017060:Patient Satisfaction; D012680:Sensitivity and Specificity; D014741:Video Recording
chemical_list: D002400:Cathartics