Percent predicted forced vital capacity–based staging in chronic obstructive pulmonary disease: A prospective, multicenter cohort study

Abstract Percent predicted forced expiratory volume in 1 s (ppFEV 1 ) is widely used to grade the severity of chronic obstructive pulmonary disease (COPD); however, it has limited prognostic accuracy. Percent predicted forced vital capacity (ppFVC) may offer complementary prognostic information. This study aimed to determine whether a ppFVC-based severity staging system predicts all-cause mortality and moderate-to-severe exacerbations in patients with COPD, and to assess its prognostic value across different Global Initiative for Chronic Obstructive Lung Disease (GOLD) stages. In this prospective, multicenter cohort study, 370 patients with COPD were enrolled and followed for 5 years. COPD diagnosis and GOLD staging were based on pre-bronchodilator spirometry. Patients were classified into four severity stages based on ppFVC (ppFVC ≥ 100%, 80% ≤ ppFVC < 100%, 60% ≤ ppFVC < 80%, and ppFVC < 60%). All-cause mortality and moderate-to-severe COPD exacerbations were evaluated as clinical outcomes. Associations between ppFVC-based stages and outcomes were analyzed using multivariable Cox proportional hazards models for mortality and Fine–Gray subdistribution hazards models for exacerbations, adjusting for relevant clinical covariates. During the follow-up period, 48 deaths and 91 moderate-to-severe exacerbations were recorded. All-cause mortality differed significantly across the ppFVC-based stages ( P for trend < 0.01), with the highest mortality observed in ppFVC-based stage IV. Compared with patients with ppFVC ≥ 100%, the multivariable-adjusted hazard ratios for mortality were 2.90, 2.07, and 13.39 for ppFVC categories of 80% ≤ ppFVC < 100%, 60% ≤ ppFVC < 80%, and ppFVC < 60%, respectively. A stepwise increase in exacerbation risk was observed ( P for trend < 0.01), with adjusted subdistribution hazard ratios of 3.03, 4.73, and 9.16 across the same ppFVC categories. In subgroup analyses, no significant associations were observed in patients with GOLD stages I–II, whereas ppFVC-based staging provided further stratification of both mortality and exacerbation risk among patients with GOLD stages III–IV. Model-comparison analyses demonstrated that ppFVC provided incremental prognostic information for all-cause mortality beyond ppFEV 1 and GOLD stage. ppFVC-based staging is a significant predictor of all-cause mortality and moderate-to-severe exacerbations in COPD and provides complementary prognostic information to ppFEV 1 , particularly in advanced disease. Incorporating assessment of FVC alongside FEV 1 may facilitate clinical risk stratification in patients with COPD.