Reduced FEV1/FVC and FEV1 in the Normal Range as a Physiological Variant

BACKGROUND: Healthy individuals without respiratory symptoms can sometimes present with low FEV1/FVC. The objective of this study was to characterize and compare subjects without symptoms and with reduced FEV1/FVC but normal FEV1 with subjects with mild obstructive lung disease. METHODS: Fifty healthy subjects with FEV1/FVC below the fifth percentile of reference values (normal variants) were compared with 52 subjects with asthma and 48 subjects with COPD who had similar FEV1/FVC. RESULTS: Subjects without symptoms were more likely to be male, younger, and taller, and to have higher FVC%, FEV1%, mid expiratory flow, and terminal flow than subjects with obstructive disease. A receiver operating characteristic curve analysis determined that the best separation between the groups was provided by age < 55 y, height >= 167 cm, and FVC > 105%. A logistic regression analysis confirmed that male sex, age, FVC%, and FEF75 (Forced expiratory flow in 75% of forced vital capacity) were significant factors for discriminating subjects without symptoms from those with obstructive lung disease. CONCLUSIONS: A reduced FEV1/FVC may be a normal finding in younger-to-middle age male subjects with an FVC% value above the mean predicted value, especially when terminal flow is within the normal range.