Risk Factors for Persistent Preserved Ratio Impaired Spirometry

Preserved ratio impaired spirometry (PRISm) is a common lung function impairment associated with morbidity and mortality. It is characterized by a volatile pattern, with different subsets of PRISm trajectories having different clinical implications. Persistent PRISm, defined as FEV₁ < lower limit of normal (LLN) with FEV₁/forced vital capacity (FVC) ≥ LLN at multiple time points, is associated with higher risk of hospitalization and mortality compared to nonpersistent PRISm. The factors that predispose patients to the development of persistent PRISm remain unclear. Our objective was to identify the prevalence of persistent PRISm and its associated risk factors in a retrospective spirometry database.

We performed an analysis that included individuals with multiple spirometries and at least one finding of PRISm. Using race-neutral Global Lung Function Initiative (GLI) equations, we identified the prevalence, and compared the characteristics, between individuals with persistent or nonpersistent PRISm. We created parsimonious multivariable logistic regression models to identify factors associated with persistent PRISm.

Persistent PRISm was identified in 40% (191/479) of individuals with multiple spirometries and at least one PRISm spirometry. In the adjusted analysis, a referral for restrictive respiratory disease was associated with higher odds of persistent PRISm (odds ratio [OR] = 3.60, 95% CI 1.74-7.64) in comparison to having no disease diagnosis. Moderate (OR = 2.64, 95% CI 1.67-4.20) and severe (OR = 3.89, 95% CI 1.07-18.02) lung function impairment based on FEV₁ Z score were associated with higher odds of persistent PRISM in comparison to mild or no impairment.

Persistent PRISm was associated with referral for restrictive respiratory disease and lower lung function.