Intraobserver and interobserver reliability in sonographic size measurements of gallbladder polyps

Objectives To evaluate the intraobserver and interobserver reliability of gallbladder polyp measurements using transabdominal US and the factors that affect reliability. Methods From November 2017 to February 2018, two radiologists measured the maximum diameter of 91 gallbladder polyps using transabdominal US. Intraobserver and interobserver agreement were determined using 95% Bland-Altman limits of agreement and intraclass correlation coefficients (ICCs). The effects of image settings, polyp location, and polyp size were evaluated by comparing ICCs using z tests. Results The intraobserver agreement rates were 0.960 (95% confidence interval [CI], 0.939–0.973) for observer 1 and 0.962 (95% CI, 0.943–0.975) for observer 2. The ICCs between the two observers were 0.963 (95% CI, 0.926–0.979) for the first measurement and 0.973 (95% CI, 0.950–0.984) for the second measurement. The 95% limits of agreement on repeated measurements were 22.3–25.2% of the mean, and those between the two observers were 25.5–34.2% of the mean. ICCs for large polyps (≥ 5 mm) were significantly higher than those for small polyps (