FEV 6 as a surrogate for FVC in detecting airways obstruction and restriction in the workplace

Compared with measurements of forced vital capacity (FVC), using the forced expiratory volume in six seconds (FEV 6 ) reduces test time and frustration. It was hypothesised that using FEV 6 in the workplace setting would result in an acceptably low misclassification rate for detecting airways obstruction and spirometry-defined restriction when compared with using the traditional FVC. Experienced technicians from the National Institute for Occupational Safety and Health performed spirometry using dry rolling-seal spirometers as per American Thoracic Society guidelines in four workplace investigations. Airways obstruction was defined as an FEV 1 /FVC % below the lower limit of normal (LLN) using National Health and Nutrition Examination Survey III reference equations. Restriction was defined as an FVC below the LLN with a normal FEV 1 /FVC %. These “gold standard” definitions were compared with definitions based on FEV 6 (obstruction: FEV 1 /FEV 6 below the LLN; restriction: FEV 6 below the LLN with a normal FEV 1 /FEV 6 ). The median (range) age of the 1,139 workers was 37 yrs (18–71 yrs) and 51.4% were male. A significantly high overall agreement was obtained between the two definitions. In conclusion, the current results confirm that forced expiratory volume in six seconds can be used as a surrogate for forced vital capacity in detecting airways obstruction and restriction in workers, although with some misclassification when compared to obtaining American Thoracic Society-acceptable manoeuvres of longer duration.