Airflow Obstruction Categorization Methods and Mortality

Rationale: Current guidelines recommend using forced expiratory volume in 1 second (FEV1) % predicted to categorize the severity of airflow obstruction. There are limitations to using FEV1 % predicted for this purpose, including bias associated with demographic factors and the inability to correct for “lung size.” Other methods for grading the severity of airflow obstruction have been proposed to address these limitations.Objectives: Our objectives were to categorize airflow obstruction severity using these methods and then determine which method results in a categorization most closely associated with mortality.Methods: Study subjects were patients aged 40–80 years tested in our pulmonary function test laboratories in the period 2002 to 2013 with airflow obstruction based on an FEV1/forced vital capacity (FVC) less than the lower limit of normal. Categorization of airflow obstruction severity was determined using four methods: FEV1 % predicted; FEV1 % predicted adjusted by FVC % predicted; FEV1/FVC confi...