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

BACKGROUND: Forced expiratory volume in 6 s (FEV6) has been proposed as a more easily measurable parameter than forced vital capacity (FVC) to diagnose airway disease using spirometry. A study was undertaken to estimate FEV6 repeatability, to identify correlates of a good quality FEV6 measurement and of volumetric differences between FEV6 and FVC in elderly patients. METHODS: 1531 subjects aged 65-100 years enrolled in the SA.R.A project (a cross-sectional multicentre non-interventional study) were examined. FEV6 was measured on volume-time curves that achieved satisfactory start-of-test and end-of-test criteria. Correlates of FEV6 achievement were assessed by logistic regression. 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 patients with airway obstruction were 94% and 78.4%. Both FEV6 and FVC repeatability were affected by male sex and lower education. Male sex, airway obstruction and smoking habit were independently associated with greater volumetric differences between FEV6 and FVC. CONCLUSIONS: In elderly patients, FEV6 measurements are more easily achievable and more reproducible than FVC although 1/6 patients in this population were unable to achieve them.