Longitudinal transitional states of spirometric patterns: the LEAD study

Spirometry serves to diagnose normal airflow (FEV₁/FVC ≥0.70); airflow limitation (AL; FEV₁/FVC <0.70) with preserved (pFlow; ≥80% pred.) or reduced (rFlow; <80% pred.) FEV₁; or preserved ratio impaired spirometry (PRISm; FEV₁/FVC≥0.70 and FEV₁<80% pred.). The pulmonary changes in transitional states of these spirometric patterns were clarified in the population-based Austrian LEAD study at Phases 1 (P1) and 2 (P2). Of 11547 subjects (18-82 years) with valid post-bronchodilator spirometric measurements, 7233 were re-examined after 4.3±0.7 years and categorised into different spirometric patterns. The prevalence rates of AL, regardless of FEV₁, (6.9%, 10.6%) and PRISm (2.8%, 2.4%) were consistent at P1 and P2. PRISm subjects exhibited substantial rates of transition: 41.8% to normal, 12.6% to rFlow and 1.9% to pFlow. Interestingly, pFlow subjects remained stable (68.4%), with none transiting to PRISm-P2. Some AL subjects at baseline transitioned to normal (rFlow-P1, 8.6% and pFlow-P1, 21.1%). Baseline FVC and FEV₁ %pred.GLI were notably lower in persistent PRISm than in those who transited to either rFlow or pFlow at P2 (p<0.001). Persistent pFlow subjects retained similar baseline lung measurements to those who transit to normal-P2 but have reduced values when transiting to rFlow-P2. Changes in FEV₁ and FVC %pred. were alike between persistent normal and pFlow, but different to persistent PRISm or rFlow (p<0.001). Incident PRISm (normal or AL -P1 and PRISm-P2) also experienced the largest changes in pulmonary measurements compared to incident AL (normal or PRISm -P1 and AL-P2). Our data illustrates the need for repeated spirometric assessments for accurate monitoring of impairment and/or disease conditions.