Validation of FEV6 in the elderly: correlates of performance and repeatability

Forced expiratory volume in six seconds (FEV6) has been proposed as a more easily measurable parameter than forced vital capacity (FVC) to diagnose airway disease using spirometry. We aimed to estimate FEV6 repeatability, to identify correlates of a good quality FEV6 and of volumetric differences between FEV6 and FVC in elderly patients. We examined 1531 subjects aged 65-100 yrs enrolled in the Sa.R.A project (cross-sectional, multicenter, non interventional study). FEV6 was measured on volume-time curves that achieved both a satisfactory start of test and end of test. Correlates of FEV6 achievement were assessed by logistic regression. FEV6 and FVC were obtained in respectively 82.9%, and 56.9% of spirometries with acceptable start of test. Female sex, older age, lower educational level, depression, cognitive impairment and lung restriction independently affected the achievement of FEV6. A good repeatability (difference between the best two values <150ml) was found in 91.9% of tests for FEV6 and in 86% for FVC; the corresponding figures in obstructed patients were 94% and 78.4%. Both FEV6 and FVC repeatability were affected by male sex and lower education. Finally, male sex, airway obstruction and smoking habit were independently associated with greater volumetric differences between FEV6 and FVC. In elderly patients, FEV6 is more easily achievable and more reproducible than FVC, although in this population still 1 out 6 patients could not achieve it.