What defines spirometry: pulmonary and extrapulmonary traits behind spirometric patterns

The Global Initiative for Chronic Obstructive Lung Disease (GOLD) establishes airflow limitation (AL) dichotomised by FEV₁/FVC <0.7 and its severity by FEV₁ %pred. This study aims to classify spirometric patterns globally by employing a similar dichochotomy: subjects with preserved ratio and reduced FEV₁ (PRISm); and AL assessed by reduced FEV₁ (rFlow, <80 %pred.GLI) or preserved FEV₁ (pFlow, ≥80 %pred.GLI). Associations between these patterns and baseline pulmonary and extrapulmonary characteristics were explored in the population-based Austrian LEAD study. Among 11547 subjects (18-82 years) with valid post-bronchodilator spirometry, 3.5% had PRISm, 4.1% pFlow and 3.0% rFlow. Lung volumes differed between groups with FEV₁/FVC<0.7: rFlow were associated with higher RV/TLC while pFlow had the highest TLC and significantly reduced RV/TLC than rFlow. rFlow subjects also had the lowest MMEF (39.3±11.3 %pred.) and sGAW (0.8±0.4 1/kPa/s) compared to pFlow subjects (who shared similar sGAW with PRISm (1/kPa/s: 1.3±0.4 and 1.5±0.7)). Subjects with FEV₁/FVC<0.7 were generally older (58.7±13.6 y) than their counterparts (PRISm, 45.9±18.3 y; normals, 44.9±16.9 y). An opposing effect of body composition (increased fat mass and visceral adipose tissue but decreased skeletal muscle mass) was found in FEV₁ <80%pred. threshold groups against their counterparts. Respiratory symptoms (dyspnoea, chronic cough, phlegm) varied significantly among spirometric pattern, with rFlow reporting the highest burden and pFlow markedly the lowest. Our data confirm clinical differences within participants with reduced FEV₁/FVC ratio and that diseased states based on the GOLD-defined FEV₁ threshold should be contended.