How to interpret reduced FEV1/VC ratio with normal FEV1

Whether the combination of low FEV1/VC ratio with normal FEV1 represents a physiological variant or a sign of early airflow obstruction is unknown. We studied 40 subjects presenting with low FEV1/VC but FEV1 within the range of normality predicted by ERS reference equations and 10 healthy controls. All subjects completed two questionnaires and underwent comprehensive pulmonary function testing , which included methacholine challenge and single-breath nitrogen wash-out. According to the questionnaires, the subjects were assigned to three groups, i.e. rhinitis (n=8), bronchial asthma (n=13) and COPD (n=12). Subjects with negative responses to questionnaires were assigned to an asymptomatic group (n=7). Airway hyperresponsiveness was found in 4 subjects of the rhinitis group, all of the asthma group, 10 of the COPD group and was associated in the last two groups with signs of increased airway closure and gas trapping. Bronchodilator response to salbutamol was positive in only few individuals across groups. In the subjects of the asymptomatic group, no significant functional changes were observed, possibly suggesting dysanaptic lung growth. In subjects with low FEV1/VC and normal FEV1, questionnaires on respiratory symptoms together with additional pulmonary function tests may help to clarify the nature of this pattern of lung function.