Computed Tomography Bronchus Sign Subclassification during Radial Endobronchial Ultrasound-Guided Transbronchial Biopsy: A Retrospective Analysis

Abstract

The presence of computed tomography bronchus sign (CT-BS) substantially increases the diagnostic yield of peripheral pulmonary lesions. However, the clinical significance of subdividing CT-BS remains controversial. We classified bronchus types on CT into six subtypes (CT-BS group I: types Ia-Ic with the bronchus connected within the lesion, group II: types IIa-IIc without connection) to clarify the differences in their characteristics and investigate the factors associated with diagnosis during radial endobronchial ultrasound (rEBUS)-guided bronchoscopy. In total, 1021 cases were analyzed. Our findings in diagnostic yields were that in CT-BS group I, penetrating type Ic was inferior to obstructed type Ia and narrowing type Ib (59.0% vs. 80.0% and 76.3%, p < 0.001, p = 0.004); in CT-BS group II, compressed type IIa showed no difference when compared with invisible type IIb and uninvolved type IIc (IIa: 52.8% vs. IIb: 46.3% and IIc: 35.7%, p = 0.253). Multivariable analysis revealed that bronchus type (types Ia and Ib vs. Ic) was a significant independent predictor of successful diagnosis in CT-BS group I (odds ratio, 1.78; 95% confidence interval, 1.04-3.05; p = 0.035), along with known factors such as rEBUS visualization. CT-BS subclassification may provide useful information regarding the bronchoscopic technique to facilitate accurate diagnosis.

Keywords: bronchoscopy; bronchus sign; lung cancer; peripheral pulmonary lesion; radial endobronchial ultrasound.

Figure 1

Schematic of classification of bronchus types, integrated with previously reported classifications. CT-BS, computed tomography bronchus sign [10,18,20,21,25].

Figure 2

Study cohort flowchart. rEBUS-TBB, radial endobronchial ultrasound guided transbronchial biopsy; CT, computed tomography; CT-BS, CT bronchus sign.

Figure 3

Diagnostic yields of each rEBUS finding in CT-BS groups (a) I and (b) II. In cases with a “within” image, type Ic had a lower diagnostic yield compared with types Ia and Ib (p < 0.001 and <0.001, respectively). In cases with an “adjacent to” image, there was no difference in diagnostic yield between the bronchus types in CT-BS group I (p = 0.621). In CT-BS group II, there was no difference in diagnostic yields of “within” and “adjacent to” images between the bronchus types (p = 0.774 and 0.955, respectively). rEBUS, radial endobronchial ultrasound; CT-BS, computed tomography bronchus sign.

Figure 4

Diagnostic yields of each forceps in CT-BS groups (a) I and (b) II. The difference in diagnostic yield between the 1.9- and 1.5 mm forceps was the greatest in group Ic but not significant in CT-BS group I (58.2% [53 of 91] vs. 42.9% [6 of 14], p = 0.387). Compared with other bronchus types, 1.5 mm forceps cases had a higher diagnostic yield than 1.9 mm forceps cases in type IIb (58.1% [25 of 43] vs. 40.4% [19 of 47], p = 0.139). CT-BS, computed tomography bronchus sign.