Intra- and interobserver agreement of endoscopic sonoelastography in the evaluation of lymph nodes

There is a lack of studies on the intra- and interobserver variability of endoscopic ultrasonography (EUS) and especially endoscopic sonoelastography (ES). The aim of this study was to evaluate the intra- and interobserver agreement of EUS and ES during the evaluation of a specific lymph node in patients with upper gastrointestinal malignancies (UGIM). The ES strain ratio was used to differentiate between benign and malignant lymph nodes and the interobserver agreement was evaluated.

This study prospectively enrolled 62 patients with UGIM. EUS and ES were performed by two observers in randomized order of a specific lymph node using a linear Pentax echoendoscope and the Hitachi EUB-8500 US unit. The lymph node was classified as malignant or benign on the basis of EUS, ES, an ES scoring system, and 5 repeated strain ratio measurements. The intraobserver variation was evaluated by each observer performing 20 strain ratio measurements of the same lymph node. Finally, EUS fine needle aspiration was performed. The kappa statistic was used to test for interobserver variability.

One patient was excluded due to inadequate ES imaging. Thus, 61 patients were included in the analysis of the interobserver agreement. Using EUS, ES, and an ES scoring system, the kappa values were 0.80, 0.58, and 0.35, respectively. An ES strain ratio of 3.81 was defined as the cut-off value between benign and malignant lymph nodes using cytology as the gold standard (n = 55). Using this modality, a kappa value of 0.59 was obtained. A t-test comparison of the measured strain ratios for the two observers found no significant differences.

ES and ES strain ratio evaluation of lymph nodes were feasible and may be reproduced with good interobserver agreement in a blinded clinical setup. The predefined ES scoring system provided only poor interobserver agreement. Image selection should be part of the intra- and interobserver evaluation. ES strain ratio seemed promising but larger studies are needed to evaluate this new feature.