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

Plumb, A.A., Boone, D., Fitzke, H., Helbren, E., Mallett, S., Zhu, S., Yao, G. L., Bell, N., Ghanouni, A., von Wagner, C., Taylor, S.A., Altman, D.G., Lilford, R. and Halligan, S. (2014) Detection of extracolonic pathologic findings with CT colonography: a discrete choice experiment of perceived benefits versus harms. Radiology, 273 (1), 144-52. (doi:10.1148/radiol.14131678). (PMID:24865308)

Abstract

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.

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