Currently, there is no standardized method to evaluate operator reliability in nerve ultrasound. A short prospective protocol using Bland-Altman analysis was developed to assess the level of agreement between operators with different expertise levels. A control rater without experience in nerve ultrasound, three novices after two months of training, an experienced rater with two years of experience, and a reference rater performed blinded ultrasound examinations of the left median and ulnar nerve in 42 nerve sites in healthy volunteers. The precision of Bland-Altman agreement analysis was tested using the Preiss-Fisher procedure. Intraclass correlation coefficients (ICC), coefficients of variation, and Bland-Altman limits of agreement were calculated. The sample size calculation and Preiss-Fisher procedure showed a sufficient precision of Bland-Altman agreement analysis. Limits of agreement of all trained novices ranged from 2.0 to 2.9 mm2 and were within the test's maximum tolerated difference. Ninety-five percent confidence intervals of limits of agreement revealed a higher precision in the experienced rater's measurements. Operator reliability in nerve ultrasound of the median and ulnar nerve arm nerves can be evaluated with a short prospective controlled protocol using Bland-Altman statistics, allowing a clear distinction between an untrained rater, trained novices after two months of training, and an experienced rater.
Keywords: Bland–Altman agreement analysis; cross-sectional area; nerve ultrasound; reliability; training effect.