Asthma with Preserved Ratio Impaired Spirometry: A Distinct Phenotype Associated with Increased Exacerbation Burden

Asthma is a heterogeneous disease, and identifying phenotypes associated with an increased exacerbation burden is clinically important. Preserved ratio impaired spirometry (PRISm) has been linked to adverse health outcomes; however, its clinical impact on asthma remains incompletely defined. The aim of this study was to determine whether asthma with PRISm represents a distinct clinical phenotype characterised by an increased exacerbation burden.

We retrospectively analysed data from 1,411 adult patients with asthma. The patients were categorised into three groups according to %FEV₁ and FEV₁/FVC: control (n=1102), PRISm (n=133), and airflow obstruction groups (n=176). Clinical characteristics and asthma exacerbation profiles were compared among the groups.

Age, sex, smoking status, and body mas index (BMI) significantly differed among the groups. The PRISm group had a significantly higher frequency of severe acute exacerbations than the control group, whereas no significant difference was observed between the PRISm and airflow obstruction groups. Severe asthma was more frequent in the PRISm group than in the control group, but its frequency was comparable between the PRISm and airflow obstruction groups. In multinomial logistic regression analysis, relative to the control group, the PRISm group was characterised by higher BMI (1.08 (1.03-1.13), adjusted odds ratio (95% confidence interval)), longer asthma duration (1.02 (1.00-1.03)), and higher severe acute exacerbation (2.31 (1.46-3.64)). Relative to the airflow obstruction group, the PRISm group was characterised by higher BMI (1.15 (1.07-1.24)) and shorter asthma duration (0.97 (0.96-0.99)), while the frequency of severe acute exacerbations (1.39 (0.78-2.48)) did not differ significantly between them.

Asthma with PRISm may represent a distinct and clinically relevant phenotype associated with a substantial exacerbation burden. Its clinical importance lies not merely in its spirometric profile, but in the identification of a subgroup of patients who may require closer surveillance and earlier optimisation of management.