Validation of virtual colonoscopy in the detection of colorectal polyps and masses: rationale for proper study design

Colorectal cancer, the second-leading cause of cancer-related mortality, is a preventable malignancy in many cases. Despite the availability of several screening modalities, compliance with screening recommendations remains unacceptably low. Virtual colonoscopy is a novel, minimally-invasive technique with the potential to increase colorectal cancer screening rates, but its effectiveness must first be validated. Published studies comparing virtual colonoscopy to conventional colonoscopy have reported varying results. These discrepancies may be attributed to differences in bowel preparation and scanning techniques, as well as errors in endoscopic lesion measurement, endoscopic colonic segmental localization, and the ability of conventional colonoscopy to actually detect lesions. These methodological issues can affect scientific results and ultimately affect the public's perception of this emerging technique.

The goal of this report is to expose existing methodological shortcomings and propose solutions incorporated in this study design. This article describes the rationale, study design, and outcome definitions of a single-center, blinded, direct comparative trial aiming at assessing the ability of virtual colonoscopy to detect colorectal polyps and masses relative to the criterion standard, conventional colonoscopy. DESIGN FEATURES: Bowel preparation was standardized using oral sodium phosphate lavage, orally administered iodinated contrast, and controlled colonic insufflation. Segmental unblinding allowed a second-look when results were discrepant and polyp matching was performed using an algorithm based on segmental localization and lesion size determination.

This methodology could be applied to other studies assessing the accuracy of virtual colonoscopy in order to have uniformity of results.