High positive predictive value of CT colonography in a referral centre

To assess the positive predictive value (PPV) of CTC in the clinical routine of a dedicated referral centre.

All consecutive patients referred for CTC between May 2009 and May 2010 were considered for inclusion in this study. All the patients who, following the diagnosis of a>6 mm polyp or mass at CTC, underwent a post-CTC colonoscopy within eight weeks from diagnosis were included. Per patient PPV for lesions, adenomas and advanced neoplasia was calculated. Chi-square test was used for statistical comparison, and a p value<0.05 was considered to be statistically significant.

516 patients were included in the study. Of them, 76 (14%) patients had at least one lesion≥6 mm on CTC. Overall, 59 (11%) patients were diagnosed at CTC with at least one polyp, 12 (2%) with a flat lesions, and 5 (1%) with a mass. Per-patient PPVs for any lesion>6 mm, neoplasia, and advanced neoplasia were 96% (95% CI: 92-100%), 68.4% (95% CI: 58-79%), and 30% (95% CI: 20-41%), respectively. PPV for neoplasia and advanced neoplasia was substantially higher for >10 mm lesions.

In dedicated centers, CTC appears to be a highly specific procedure, characterized by a very low rate of false-positive results for >6 mm lesions.