Expanded detection of early fibrotic phenotypes using lobar traction bronchiolectasis in lung cancer screening.

RATIONALE: Lung cancer screening regularly identifies participants with interstitial lung abnormalities (ILA). Existing classification methods may underestimate the prevalence of clinically relevant ILA phenotypes.

OBJECTIVES

Can a classification system for ILAs developed in a lung cancer screening setting identify clinically relevant phenotypes?

METHODS

Classification criteria based on the presence and lobar extent of traction bronchiolectasis (TBe) were developed internally by expert consensus. Categories included: no ILA, non-fibrotic ILA (NF-ILA), fibrotic ILA (F-ILA), and undiagnosed fibrotic ILD (U-ILD). Interobserver agreement was calculated between two readers. Clinical characteristics, respiratory hospitalizations, and survival were compared between participants of different ILA grades.

MEASUREMENTS AND MAIN

RESULTS

Eight thousand, one hundred sixty-nine participants were included in the final analysis. TBe showed improved interobserver agreement compared to the American Thoracic Society (ATS) classification, identifying 344 participants (4%) with U-ILD, 86% more than the ATS classification. An additional 405 had F-ILA (5%) and 667 had NF-ILA (8%). Compared to participants without ILA, participants with U-ILD had a higher rate of respiratory hospitalization (IRR = 4.4, 95% CI 2.7-7.5, P < .001) and increased risk of death (aHR = 2.4, 95% CI 1.9-3.0, P < .001). Increasing ILA grade was associated with higher modified Medical Research Council dyspnea scores (OR = 1.1, 95% CI 1.0-1.1, P = .02).

CONCLUSIONS

In a lung cancer screening setting, an ILA scoring system focused on lobar TBe identifies more high-risk participants and demonstrates improved interobserver concordance than the ATS classification. TBe identifies participants with a respiratory phenotype who may warrant further investigation and follow-up.