Accuracy of computed tomographic colonography in a nationwide multicentre trial, and its relation to radiologist expertise

Objective Reports on the accuracy of computed tomographic colonography (CTC) mainly involve series from expert institutions. The aims of this study were to assess CTC accuracy in a nationwide population and to relate it to radiologist performance in their initial training. Design Nationwide multicentre trial. Setting Twenty-eight radiologists, working in 26 mostly academic clinical units, were involved in the study after having attended a formal specialised 2-day training session on CTC. They worked through a training set of 52 cases with automatic feedback after an attempt at each case. Patients The study enrolled 845 patients with average and high risk of colorectal cancer, 737 of whom had both complete CTC and videocolonoscopy data, which constituted the dataset. Interventions Patients underwent same-day CTC followed by videocolonoscopy with segmental unblinding of CTC results. Main outcome measures Sensitivity, specificity and positive and negative predictive values for detection of polyps ≥6 mm in per-patient and per-lesion analyses of CTC without computer-aided detection. Results Sensitivity, specificity and positive and negative predictive values for patients with polyps ≥6 mm were 69% (95% CI 61% to 77%), 91% (95% CI 89% to 94%), 67% (95% CI 59% to 74%) and 92% (95% CI 90% to 94%), respectively. Univariate analysis showed that the detection rate for polyps ≥6 mm was linked to neither radiologist case volume nor number of polyps, but was related to sensitivity achieved in the training set. Pooled sensitivity was 72% (95% CI 63% to 80%) versus 51% (95% CI 40% to 60%) for radiologists achieving above and below median sensitivity in the training set (61%), respectively. Multivariate analysis showed that sensitivity for polyps ≥6 mm in the training set was the only remaining significant predictive factor for subsequent performance. Conclusions Radiologist sensitivity CTC for detection of polyps ≥6 mm in training was the sole independent predictor for subsequent sensitivity in detection of such polyps.