The Association of Interstitial Lung Abnormalities and Preserved Ratio Impaired Spirometry (PRISm) with Mortality.

Abstract

Background: Preserved ratio impaired spirometry (PRISm) is heterogeneous and includes restrictive lung disease. Interstitial lung abnormalities (ILA) may represent early interstitial lung disease. The relationship between PRISm and ILA is not well understood.

Research question: What is the prevalence of ILA in PRISm compared to normal spirometry, what are risk factors for ILA within PRISm, and how do ILAs modify the association of PRISm and mortality?

Study design and methods: In COPDGene participants with baseline spirometry and chest computed tomography (CT) scans, we examined those with normal spirometry (FEV₁ ≥ 80% predicted and FEV₁/FVC ≥ 0.7) and PRISm (FEV₁ < 80% predicted with FEV₁/FVC ratio ≥ 0.7) with and without ILA, per Fleischner Society guidelines. We used logistic regression to examine the odds of ILA in PRISm. We modeled all-cause mortality with Cox regression. We evaluated the association of baseline ILA status on change in spirometry at followup.

Results: We included 4,494 normal spirometry and 1,262 PRISm participants. ILAs were present in 93 (7%) participants with PRISm, and 180 (4%) participants with normal spirometry. PRISm was associated with increased odds (1.74, 95% CI 1.33-2.27, p < 0.001) of ILA compared with normal spirometry. Among participants with PRISm, older age, increased smoke exposure, lower lung function, and increased airway wall thickness were associated with ILA. ILAs were associated with increased mortality (adj. HR 2.58, [95%CI:1.49-4.45]).

Interpretation: Within PRISm, ILA is associated with increased all-cause mortality, as well as increased age, smoke exposure, lower lung function, and increased airway wall thickness.