Interobserver reliability of Masei index validation by a multicenter collaborative group of rheumatologists.

MASEI is the main validated ultrasound score for the evaluation of enthesis. The lack of studies facing the agreement to achieve for the interpretation of the MAdrid Sonographic Enthesis Index (MASEI) among researchers from different centers in multicenter studies is of concern. The aim of this multicenter was to evaluate the interobserver reliability of MASEI. An experienced ultrasonographer-rheumatologist performed ultrasound scans of the areas included in MASEI index in three patients with Ankylosing Spondylitis and Psoriatic Arthritis. Videos were captured. The videos were then evaluated by 24 rheumatologists of the ultrasound working group of the Catalan Society of Rheumatology (EcoCAT). A face-to-face training meeting was held. Ten days after the workshop, the study participants evaluated the videos. A reliability assessment was performed. The ICC for the MASEI scores after the workshop was of 0.97 (95% CI 89-99). Reliability did not vary statistically with examiner experience. Globally, no problems of reliability by structures were seen, and all the ICCs were above 0.90 and improved slightly after the educational program. However, the correlation observed between examiners at plantar aponeursis and triceps tendon was weak. The small variability observed in the results of the index validation in our study, suggests that the MASEI index is reproducible by different observers when those are well trained and show awesome results of the enthesis when examined by ultrasound.