OBJECTIVE(S): During endobronchial ultrasound (EBUS) staging, ultrasonographic features can be used to predict mediastinal lymph node (LN) malignancy. We sought to develop the Canada Lymph Node Score a tool capable of predicting LN metastasis at the time of EBUS.
METHODS: Patients undergoing EBUS staging for lung and esophageal cancer were prospectively enrolled. Features were identified in real time by an endoscopist and video-recorded. Videos were sent to raters. Pathologic specimens from biopsies/surgical resections were used as the gold-standard reference test. Logistic regression, receiver operator characteristic curve, and Gwet's AC1 analyses were used to test the performance, discrimination, and inter-rater reliability, respectively.
RESULTS: In total, 300 LNs from 140 patients were analyzed by 12 endoscopists (raters) across 7 Canadian centers. Beta-coefficients from a multivariate regression model were used to create a 4-point score: short-axis diameter, margins, central hilar structure, and necrosis. The model showed good discriminatory power (c-statistic = 0.72 ± 0.04, 95% confidence interval [CI], 0.64-0.80; bias-corrected c-statistic: 0.66, 95% CI, 0.55-0.76). LNs scoring 3/4 or 4/4 had odds ratios of 15.17 (P < .0001) and 50.56 (P = .001) for predicting malignancy, respectively. Inter-rater reliability for a score ≥3 was 0.81 ± 0.02 (95% CI, 0.77-0.85).
CONCLUSIONS: The Canada Lymph Node Score is a 4-point score demonstrating excellent performance in identifying malignant LNs during EBUS. A cut-off of ≥3 may inform decision-making regarding biopsy, repeat biopsy, or mediastinoscopy if the initial results are inconclusive.