To evaluate the effect of endobronchial ultrasound elastography in judging the nature of mediastinal and hilar lymph nodes by individually and jointly comparing the parameters of chest CT, ultrasound and elastography.

The persons who were admitted to the Department of Respiratory and Critical Care Medicine in Nanjing First People′s Hospital, affiliated to Nanjing Medical University for EBUS-TBNA examination from June 2016 and March 2018 were taken as the subjects for this study. An Olympus 290 bronchoscope system from Japan and an EU-ME2 ultrasound system were used. The parameters of target lymph nodes in chest CT, ultrasound and elastography were compared before EBUS-TBNA examination. The pathological results after EBUS-TBNA examination or three-month follow-up of unknown results were taken as the gold standard of diagnosis. The ROC curve of each characteristic parameter was constructed to obtain the AUC and cutoff values, and the diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of each parameter were calculated to analyze and compare the elastography for the diagnosis of lymph node properties. In addition, the parameters of elastography for different pathological types were analyzed and statistically evaluated for further diagnostic value.

Totally 78 patients, including 117 lymph nodes, were collected. According to the differentiation of the lymph node properties by chest CT, the three properties of the lymph nodes (the short diameter≥10 mm, clear boundary and uneven texture) had statistical significant differences (P<0.05). Among them, the uneven texture of the AUC was highest, 0.711. When the characteristics of the lymph nodes were determined by ultrasound, the short diameter of the lymph nodes≥10 mm, the clear boundary, low echo and the circular shape had statistical significant difference (P<0.05). Among them, the clear boundary of the AUC was highest, 0.655. Ultrasound elastography images used image types, ultrasound elasticity score, strain rate ratio and blue area ratio to determine the nature of lymph nodes, and the values of AUC were 0.843, 0.820, 0.717, and 0.877, respectively. Among them, the blue area ratio was the highest. Inhomogeneous lymph node texture in chest CT, clear boundary of lymph nodes in ultrasound combined with elastography image types were statistically analyzed, and the accuracy, sensitivity, specificity, positive predictive value, and negative predictive value were 85.5%. 85.7%, 87.9%, 100%, 100%, respectively. And the value of AUC was 0.932. The diagnostic value was significantly higher than any single factor.

The diagnostic value of ultrasound elastography for differentiating the nature of hilar and mediastinal lymph nodes is higher than that of chest CT or ultrasound. The combination of the three techniques can significantly increase the malignant detection rate of lymph nodes.