Quantitative analysis of endobronchial ultrasound elastography in computed tomography-negative mediastinal and hilar lymph nodes

Abstract

Background: Endobronchial ultrasound (EBUS) elastography assists in the differentiation of benign and malignant lymph nodes (LNs) during transbronchial needle aspiration (TBNA). However, previous studies have not compared B-mode sonographic images (BSIs) and EBUS elastography images (EEIs) with final pathological diagnoses in radiologically normal-sized (computed tomography [CT]-negative) LNs.

Methods: Consecutive patients with CT-negative LNs, who received EBUS-TBNA, were retrospectively reviewed. Images of BSIs and EEIs of each LN were stored and independently evaluated. EEIs were assessed by calculating the stiffness area ratio (SAR, blue/overall areas). The receiver operating characteristic curve was used to calculate the cutoff value for the SAR. Diagnostic test parameters were evaluated for each EBUS finding.

Results: A total of 132 patients (149 LNs) were enrolled, and the median SAR of malignant LNs was significantly higher than that of benign LNs (0.58 vs. 0.32, P < 0.001). At the SAR cutoff of 0.41, the sensitivity, specificity, positive predictive value, negative predictive value (NPV), and diagnostic accuracy rate (DAR) of elastography were 88.2%, 80.2%, 78.9%, 89.0%, and 83.9%, respectively. The logistic regression analysis showed that elastography was the strongest predictor of malignancy (odds ratio, 18.5; 95% confidence interval [CI]: 6.48-52.6; P < 0.001). The highest NPV (96.6%) was achieved with a combination of BSIs and EEIs.

Conclusions: EBUS elastography predicted malignant LNs with a high DAR and NPV in CT-negative LNs. The NPV was highest when EEIs were combined with BSIs. Therefore, the combined evaluation of CT-negative LNs using EEIs and BSIs may help bronchoscopists perform EBUS-TBNA more efficiently.

Key points: SIGNIFICANT FINDINGS OF THE STUDY: Endobronchial ultrasound elastography accurately predicted malignancy with a high diagnostic accuracy rate and negative predictive value in radiologically normal-sized lymph nodes. The additional use of B-mode sonographic features resulted in a higher negative predictive value.

What this study adds: Endobronchial ultrasound elastography can guide the accurate collection of specimens with transbronchial needle aspiration, even in radiologically normal-sized lymph nodes. It can also readily distinguish benign and malignant lymph nodes, thus avoiding unnecessary punctures.

Keywords: Bronchoscopy; elastography; endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA); lung cancer.