Obstructive and restrictive spirometric patterns: fixed cut-offs for FEV₁/FEV₆ and FEV₆

Abstract

The purpose of this study was to determine fixed cut-off points for forced expiratory volume in one second (FEV₁)/FEV₆ and FEV₆ as an alternative for FEV₁/forced vital capacity (FVC) and FVC in the detection of obstructive and restrictive spirometric patterns, respectively.

For the study, a total of 11,676 spirometric examinations, which took place on Caucasian subjects aged between 20–80 yrs, were analysed. Receiver–operator characteristic curves were used to determine the FEV₁/FEV₆ ratio and FEV₆ value that corresponded to the optimal combination of sensitivity and specificity, compared with the commonly used fixed cut-off term for FEV₁/FVC and FVC.

The data from the current study indicate that FEV₁/ FEV₆ <73% and FEV₆ <82% predicted can be used as a valid alternative for the FEV₁/FVC <70% and FVC <80% pred cut-off points for the detection of obstruction and restriction, respectively. The statistical analysis demonstrated very good, overall, agreement between the two categorisation schemes. For the spirometric diagnosis of airway obstruction (prevalence of 45.9%), FEV₁/FEV₆ sensitivity and specificity were 94.4 and 93.3%, respectively; the positive and negative predictive values were 92.2 and 95.2%, respectively. For the spirometric detection of a restrictive pattern (prevalence of 14.9%), FEV₆ sensitivity and specificity were 95.9 and 98.6%, respectively; the positive and negative predictive values were 92.2 and 99.3%, respectively.

This study demonstrates that forced expiratory volume in one second/forced expiratory volume in six seconds <73% and forced expiratory volume in six seconds <82% predicted, can be used as valid alternatives to forced expiratory volume in one second/forced vital capacity <70% and forced vital capacity <80% predicted, as fixed cut-off terms for the detection of an obstructive or restrictive spirometric pattern in adults.