Preserved Ratio Impaired Spirometry (PRISm) and Serum Matrix Metalloproteinase-9 (MMP-9) Levels as Early Markers of Lung Obstruction in Active Smokers

Abstract

PRISm is defined by reduced forced expiratory volume in one second (FEV1 <80% predicted) with a preserved FEV1/forced vital capacity (FVC) ratio (≥0.70). Recognized as early stage of chronic obstructive pulmonary disease (COPD) in smokers, it remains underdiagnosed. This study compared MMP-9 in Indonesian smokers with PRISm versus non-PRISm and its association with PRISm status. This cross-sectional study enrolled 88 asymptomatic smokers among hospital security personnel in Makassar, Indonesia. Participants underwent interviews, anthropometry, ATS/ERS-standard spirometry, and serum MMP-9 ELISA. They were classified as PRISm or non-PRISm. Groups were compared using Mann-Whitney U/chi-square tests; logistic regression adjusted for age, BMI, Brinkman Index; ROC assessed MMP-9 discrimination. PRISm was identified in 58 of 88 participants (65.9%). Versus the non-PRISm group, the PRISm group had lower FEV1, FVC, and FEF25–75% (all p<0.001), with no difference in FEV1/FVC (p=0.672). Median serum MMP-9 was higher in PRISm (259.50 [IQR 197.00–428.50] vs. 116.50 [IQR 48.75–192.25] ng/mL; p<0.001). ROC analysis showed discrimination (AUC 0.812; 95% CI 0.718–0.906); ≥158 ng/mL gave 77.6% sensitivity, 76.7% specificity, and independent association with PRISm after adjustment (adjusted OR 12.80; 95% CI 4.19–39.12; p<0.001). PRISm was common in active smokers and independently associated with elevated serum MMP-9, supporting a biomarker role in subclinical airway inflammation and remodeling. Serum MMP-9 may complement spirometry for early detection of lung impairment, pending external validation before clinical application.