FEV1/FVC Severity Stages for Chronic Obstructive Pulmonary Disease.

Abstract

The diagnosis of COPD is based on low ratio of the forced expiratory volume in one second to the forced vital capacity (FEV1/FVC) but its severity is classified using percentage predicted FEV1 (ppFEV1). To test a new severity classification scheme for COPD using FEV1/FVC, a more robust measure of airflow obstruction than ppFEV1. In COPDGene (n=10,132), the severity of airflow obstruction was categorized by GOLD Stages I-IV (ppFEV1 ≥80, ≥50-80, ≥30-50, and <30). A new severity classification (STaging of Airflow obstruction by Ratio, STAR) was tested in COPDGene: FEV1/FVC ≥0.60 to <0.70, ≥0.50 to <0.60, ≥0.40 to <0.50, and <0.40, respectively for stages I-IV, and applied to the combined Pittsburgh SCCOR and Pittsburgh Emphysema registry cohorts for replication (n=2017). Agreement (weighted Bangdiwala B) between GOLD and new FEV1/FVC severity stages was 0.89 in COPDGene and 0.88 in the Pittsburgh cohort. In both COPDGene and the Pittsburgh cohort, in comparison to GOLD staging, STAR provided significant discrimination between the absence of airflow obstruction and Stage I for all-cause mortality, respiratory-quality of life, dyspnea, airway wall thickness, exacerbations and lung function decline. No difference was noted for emphysema, small airways disease, and 6-minute walk distance. The STAR classification system identified a greater number of adults with Stage III-IV disease who would be eligible for lung transplantation and lung volume reduction evaluations. The new severity classification scheme STAR provides discrimination for mortality similar to the GOLD classification but with a more uniform gradation of disease truncated.