CT Colonography and Computer-aided Detection: Effect of False-Positive Results on Reader Specificity and Reading Efficiency in a Low-Prevalence Screening Population

doi:10.1148/radiol.2471070816

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Gastrointestinal Imaging

CT Colonography and Computer-aided Detection: Effect of False-Positive Results on Reader Specificity and Reading Efficiency in a Low-Prevalence Screening Population¹

Stuart A. Taylor, MD, MRCP, FRCR, Rebecca Greenhalgh, FRCR, Rajapandian Ilangovan, MD, FRCR, Emily Tam, FRCR, Vikram A. Sahni, FRCR, David Burling, MD, MRCP, FRCR, Jie Zhang, MD, Paul Bassett, BSc, Perry J. Pickhardt, MD, and Steve Halligan, MD, FRCP, FRCR

¹ From the Department of Specialist X-Ray, University College Hospital, 2F Podium, 235 Euston Rd, London NW1 2BU, England (S.A.T., R.G., S.H.); Department of Intestinal Imaging, St Mark's Hospital, Harrow, England (R.I., E.T., V.A.S., D.B., P.B.); Department of Radiology, Beijing Friendship Hospital, Beijing, China (J.Z.); and Abdominal Imaging Section, University of Wisconsin Medical School, Madison, Wis (P.J.P.). Received May 9, 2007; revision requested July 13; revision received August 17; accepted September 19; final version accepted October 12. Supported in part by the Department of Health's NIHR Biomedical Research Centres funding scheme. Address correspondence to S.A.T. (e-mail: csytaylor{at}yahoo.co.uk).

Purpose: To retrospectively evaluate the effect of increasing numbersof computer-aided detection (CAD)-generated false-positive (FP) markson reader specificity and reporting times by using computed tomographic(CT) colonography in a low-prevalence screening population.

Materials and Methods: Ethics committee approval and informed consentwere obtained for this HIPAA-compliant study. Four readers each read48 data sets (26 men, 22 women; mean age, 57 years) from a screeningpopulation (three containing polyps) without CAD application, followedby review of the CAD output and recorded findings and diagnosticconfidence. The 45 data sets that were designated as normal werechosen such that 22 generated 15 or fewer FP CAD marks and 23 generatedmore than 15 FP CAD marks. Sensitivity, specificity, and receiveroperating characteristic (ROC) curves were calculated with and withoutCAD. The relationships between the number of CAD FP marks and readerconfidence, reporting times, and correct data set classificationwere analyzed by using linear and logistic regression.

Results: Across all readers, CAD resulted in four additional FP detections.Overall reader sensitivity and specificity (6-mm polyp threshold)before and after CAD application were 0.75 (95% confidence interval[CI]: 0.43, 0.95) versus 0.83 (95% CI: 0.52, 0.98) and 0.96 (95%CI: 0.91, 0.98) versus 0.93 (95% CI: 0.88, 0.96), respectively. Thearea under the ROC curve increased from 0.57 (95% CI: 0.34, 0.80)to 0.61 (95% CI: 0.42, 0.80). There was no correlation between anincreasing number of CAD FP marks and reader confidence (P = .71)or correct study classification (P = .23), but there was a positivecorrelation with CAD-assisted reading times (0.06 [95% CI: 0.02,0.10], P = .002).

Conclusion: Increasing numbers of CAD FP marks did not adverselyinfluence correct reader study classification or diagnostic confidence,although reporting times did increase.