Severity of Airflow Obstruction Based on FEV1/FVC Versus FEV1 Percent Predicted in the General U.S. Population.
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.