High positive predictive value of CT colonography in a referral centre

Aim

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

Material and methods

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.

Results

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.

Conclusion

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.