All data from patients, endoscopies, and lesions were prospectively included in an anonymized data base. Continuous variables were described using median, range, and SD. Categorical values were described using percentages. The frequency of every combination of OD criteria for SSL among lesions with a pathological diagnosis of SSL was recorded, overall, and related to size, location, and previous NICE classification. Lesionʼs size was categorized in lesions ≤ 5 mm (diminutive lesions), lesions between 6 and 9 mm and lesions ≥ 10 mm. Regarding location, proximal lesions were considered when they were located proximal to left colon. The frequency of SSLs among lesions fulfilling the OD criteria was also recorded. The accuracy, sensitivity, specificity, positive and negative predictive values, and positive likelihood ratio were calculated, overall and for every endoscopist. A multivariable analysis was performed to show which variables (size, NICE classification, location) were related to a greater probability of correctly identifying an SSL. Because one patient can harbor several lesions and the lesions were inspected by the same endoscopist, for analysis purposes, the lesions cannot be considered as truly independent.

Therefore, a random-effects logistic regression model with distinguishable data should be used. The odds ratios (OR) were estimated from the model and given with their 95 % confidence intervals (95 % CI). All significance tests were two-tailed, and P values < 0.05 were considered to be statistically significant. STATA v. 14.0 software (Stata Corp., College Station, Texas, United States) was used for the data analysis.