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

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.

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.

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.

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.