Diagnostic value of endobronchial ultrasound elastography in differentiating between benign and malignant hilar and mediastinal lymph nodes: a retrospective study

Background: Endobronchial ultrasound-guided transbronchial needle aspiration ( EBUS-TBNA) is a first-line approach for diagnosing hilar and mediastinal lymph node metastasis. Endobronchial ultrasound (EBUS) elastography is an imaging technique for describing the elasticity of intrathoracic lesions. However, the reported accuracy of EBUS elastography needs to be improved. In this study, we aimed to explore the diagnostic value of EBUS elastography for differentiating between benign and malignant hilar and mediastinal lymph nodes. Methods: We conducted a single-center, retrospective study enrolling consecutive patients who received EBUS elastography followed by EBUS-TBNA at the Chinese PLA General Hospital from October 2015 to October 2022. The pathological results of EBUS-TBNA confirmed by 6-month follow-up were used as the gold standard. The ultrasound elastography parameters of lymph nodes included strain rate, stiff area ratio, and elasticity score, along with the conventional ultrasound characteristics such as short axis diameter, shape, margin, echogenicity distribution and intensity, and blood flow. The diagnostic performance of these parameters was compared, and conjointly analyzed using multivariate logistic regression. Bootstrapping resampling was applied for internal validation of the regression model. Results: A total of 83 patients were enrolled with an average age of 57 years, and 66.3% of patients were male. In total, 131 lymph nodes were punctured, among which 79 (60.3%) were malignant. All the conventional ultrasound characteristics were significantly different between benign and malignant lymph nodes. All the ultrasound elastography parameters of malignant lymph nodes were markedly higher than those of benign lymph nodes. Multivariate logistic regression analysis showed that the margin, echogenicity intensity, blood flow, short axis diameter, and stiff area ratio were the main factors affecting the lymph node property. The diagnostic accuracy, sensitivity, and specificity were 91.8% [95% confidence interval (CI): 85.4-96.0%], 94.4% (95% CI: 86.4-98.5%), and 88.0% (95% CI: 75.7-95.5%), respectively. Bootstrap resampling validation showed a concordance index (C-index) of 0.949. The calibration plot indicated good agreement between the predicted and observed results. Conclusions: EBUS elastography is a promising approach for differentiating between benign and malignant lymph nodes. The combination of conventional EBUS and elastography can improve diagnostic efficacy, provide reliable complementary information, and guide the implementation of EBUS-TBNA more accurately.