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

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.