Integrative use of conventional mode and elastography in endobronchial ultrasound for the diagnosis of malignant intrathoracic lymphadenopathy

Abstract

Background: Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) is the standard diagnostic procedure for evaluating intrathoracic lymphadenopathy. Both conventional mode and elastography aid in differentiating malignant from benign nodes. This study aimed to evaluate the diagnostic accuracy of an integrative approach combining conventional mode and elastography. Methods: A retrospective cross-sectional study was conducted in patients with intrathoracic lymphadenopathy who underwent EBUS-TBNA at Rajavithi Hospital between July 2015 and December 2018. Data were obtained from video recordings, including both conventional mode and elastography. The diagnosis of each lymph node was based on cytological or histopathological findings. Diagnostic performance was evaluated using sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), accuracy, and the area under the receiver operating characteristic curve (AUC). Logistic regression analysis was performed to evaluate the diagnostic odds ratio (DOR). Results: EBUS-TBNA was performed on 210 lymph nodes from 104 patients (mean size 17.4±9.5 mm), with 124 malignant nodes (59%) and 86 benign nodes (41%). Malignant nodes on conventional mode were associated with size >20 mm, round shape, absence of a central hilar structure (CHS), and presence of coagulation necrosis. Elastographic predictors of malignant nodes included type III (predominantly blue) and a strain ratio (SR) >12.48. In the multivariable analysis of the combined model, a SR >12.48 yielded the highest DOR (11.0), followed by absence of a CHS (4.8), round shape (3.5), coagulation necrosis (3.4), and lymph node short-axis >20 mm (3.3). The integrative use of elastography with conventional mode significantly improved diagnostic performance for distinguishing malignant lymph nodes, achieving an AUC of 0.90 [95% confidence interval (CI): 0.85–0.94], compared with 0.83 (95% CI: 0.78–0.89; P=0.002) for conventional mode alone and 0.79 (95% CI: 0.73–0.85; P<0.001) for elastography alone. Combining SR >12.48 with any single conventional feature (lymph node size >20 mm, coagulation necrosis, round shape, or absence of CHS) yielded comparably high diagnostic accuracy (AUC 0.81–0.84), with no significant differences among the combinations. Conclusions: The integrative application of conventional mode and elastography enhances the diagnostic accuracy for differentiating malignant intrathoracic lymph nodes compared with either modality alone. This combined approach provides preliminary diagnostic information that may facilitate lymph node targeting and optimize sampling strategies.