Detection of extracolonic pathologic findings with CT colonography: a discrete choice experiment of perceived benefits versus harms

Andrew A Plumb, Darren Boone, Heather Fitzke, Emma Helbren, Susan Mallett, Shihua Zhu, Guiqing L Yao, Nichola Bell, Alex Ghanouni, Christian von Wagner, Stuart A Taylor, Douglas G Altman, Richard Lilford, Steve Halligan

Research output: Contribution to journalArticlepeer-review

19 Citations (Scopus)


PURPOSE: To determine the maximum rate of false-positive diagnoses that patients and health care professionals were willing to accept in exchange for detection of extracolonic malignancy by using computed tomographic (CT) colonography for colorectal cancer screening.

MATERIALS AND METHODS: After obtaining ethical approval and informed consent, 52 patients and 50 health care professionals undertook two discrete choice experiments where they chose between unrestricted CT colonography that examined intra- and extracolonic organs or CT colonography restricted to the colon, across different scenarios. The first experiment detected one extracolonic malignancy per 600 cases with a false-positive rate varying across scenarios from 0% to 99.8%. One experiment examined radiologic follow-up generated by false-positive diagnoses while the other examined invasive follow-up. Intracolonic performance was identical for both tests. The median tipping point (maximum acceptable false-positive rate for extracolonic findings) was calculated overall and for both groups by bootstrap analysis.

RESULTS: The median tipping point for radiologic follow-up occurred at a false-positive rate greater than 99.8% (interquartile ratio [IQR], 10 to >99.8%). Participants would tolerate at least a 99.8% rate of unnecessary radiologic tests to detect an additional extracolonic malignancy. The median tipping-point for invasive follow-up occurred at a false-positive rate of 10% (IQR, 2 to >99.8%). Tipping points were significantly higher for patients than for health care professionals for both experiments (>99.8 vs 40% for radiologic follow-up and >99.8 vs 5% for invasive follow-up, both P < .001).

CONCLUSION: Patients and health care professionals are willing to tolerate high rates of false-positive diagnoses with CT colonography in exchange for diagnosis of extracolonic malignancy. The actual specificity of screening CT colonography for extracolonic findings in clinical practice is likely to be highly acceptable to both patients and health care professionals. Online supplemental material is available for this article.

Original languageEnglish
Pages (from-to)144-52
Number of pages9
Issue number1
Publication statusPublished - Oct 2014

Bibliographical note

© RSNA, 2014.


  • Aged
  • Aged, 80 and over
  • Colonography, Computed Tomographic
  • Colorectal Neoplasms
  • Early Detection of Cancer
  • False Positive Reactions
  • Humans
  • Incidental Findings
  • Middle Aged
  • Questionnaires


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