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

BACKGROUND: Forced expiratory volume in 6 s (FEV6) has been proposed as a moreeasily measurable parameter than forced vital capacity (FVC) to diagnose airwaydisease using spirometry. A study was undertaken to estimate FEV6 repeatability, to identify correlates of a good quality FEV6 measurement and of volumetricdifferences between FEV6 and FVC in elderly patients.METHODS: 1531 subjects aged 65-100 years enrolled in the SA.R.A project (across-sectional multicentre non-interventional study) were examined. FEV6 wasmeasured on volume-time curves that achieved satisfactory start-of-test andend-of-test criteria. Correlates of FEV6 achievement were assessed by logisticregression.RESULTS: Valid FEV6 and FVC measurements were obtained in 82.9% and 56.9%,respectively, of spirometric tests with an acceptable start-of-test criterion.Female sex, older age, lower educational level, depression, cognitive impairment and lung restriction independently affected the achievement of FEV6 measurement. Good repeatability (difference between the best two values <150 ml) was found in 91.9% of tests for FEV6 and in 86% for FVC; the corresponding figures in patientswith airway obstruction were 94% and 78.4%. Both FEV6 and FVC repeatability were affected by male sex and lower education. Male sex, airway obstruction andsmoking habit were independently associated with greater volumetric differencesbetween FEV6 and FVC.CONCLUSIONS: In elderly patients, FEV6 measurements are more easily achievableand more reproducible than FVC although 1/6 patients in this population wereunable to achieve them.