Severity of Airflow Obstruction Based on FEV1/FVC Versus FEV1Percent Predicted in the General U.S. Population
Helena Bäckman, Lowie E.G.W. Vanfleteren, David M. Mannino, Magnus Ekström
Abstract
Abstract Rationale According to the Global Initiative for Obstructive Lung Disease (GOLD), the FEV1/FVC ratio is used to confirm the presence of airflow obstruction in the diagnosis of chronic obstructive pulmonary disease (COPD), whereas FEV1 percent predicted normal value (FEV1%pred) is used for grading its severity. The STaging of Airflow obstruction by the FEV1/FVC Ratio (STAR), and its prediction of adverse outcomes, has not been evaluated in general populations. Objectives To compare the STAR (FEV1/FVC) and the GOLD (FEV1%pred) classifications for the severity of airflow limitation in terms of exertional breathlessness and mortality in the general U.S. population. Methods Severity stages according to the STAR and GOLD were applied to the multiethnic National Health and Nutrition Examination Survey of 2007–2012, including people ages 18–80 years, using a postbronchodilatory FEV1/FVC ratio of <0.70 to define airflow obstruction in both staging systems. Prevalence of the severity stages STAR 1–4 and GOLD 1–4 was calculated, and associations with breathlessness and mortality were analyzed by multinomial logistic regression and Cox regression, respectively. Measurements and Main Results STAR versus GOLD severity staging of airflow obstruction showed similar associations with breathlessness and all-cause mortality, regardless of ethnicity and/or race. In those with airflow obstruction, the correlation between the two classification systems was 0.461 (P < 0.001). STAR reclassified 59% of GOLD 2 subjects as having mild airflow obstruction (STAR 1). Compared with GOLD 1, STAR 1 was more clearly differentiated from nonobstruction in terms of both breathlessness and mortality. Conclusions FEV1/FVC and FEV1%pred as measures of airflow limitation severity show similar predictions of breathlessness and mortality in the adult U.S. population across ethnicity groups. However, Stage 1 differed more clearly from nonobstruction on the basis of FEV1/FVC ratio than FEV1%pred.