Inter-rater Reliability of Sonographic Optic Nerve Sheath Diameter Measurements by Emergency Medicine Physicians

Objectives To compare the degree of agreement of sonographic optic nerve sheath diameter (ONSD) measurements by ultrasound fellowship–trained and resident emergency medicine (EM) physicians. Methods Ten ultrasound fellowship–trained EM attending physicians from multiple institutions and 51 resident EM physicians at a single residency were enrolled to measure the ONSD using a computerized ruler on five separate still-frame sonograms of adult eyes that included the retrobulbar optic nerve. Descriptive and bivariate statistics for each ultrasound image were calculated to compare median ONSD measurements among groups. Intraclass correlation coefficients (ICCs) were calculated to estimate the inter-rater reliability. Results Although the median ONSD measurement of each image did not significantly differ between resident and ultrasound fellowship–trained EM physicians, we found greater variation in agreement of ONSD measurements by resident EM physicians (ICC 0.50; 95% confidence interval 0.25–0.89) than ultrasound fellowship–trained EM physicians (ICC 0.73; 95% confidence interval 0.44–0.96). Conclusions Although both resident and ultrasound fellowship–trained EM physicians showed good inter-rater reliability of ONSD measurements, variation in agreement among ultrasound fellowship–trained EM physicians may be as wide as 0.44, suggesting that even in skilled hands, ultrasound measurement of the ONSD may not be as dependable a screening tool for elevated intracranial pressure as previously suggested in the literature.