Spirometry values in a Greek population: Is there an appropriate reference equation?

Background and objective: Most published reference values for lung function test (LFT) parameters introduce systematic bias. The aim of this study was to compare measured values of FEV1 and FVC with the corresponding normal predicted values in a Greek population, and to produce reference equations for LFT parameters in this population. Methods: In a cross-sectional study conducted in Macedonia, Greece, 1080 adult healthy, non-smokers (432 men, 648 women, aged 18-80 years), underwent spirometry. Measured values of FVC and FEV1 were compared with predicted values determined using three existing sets of reference equations: one recently derived from a European population and two others widely used in Europe (European Coal and Steel Community; ECSC) and the USA (National Health and Nutrition Examination Survey; NHANES III). Height and age were entered into the multivariate regression analysis to produce reference equations for LFT parameters. Results: All three published sets of equations underpredicted FEV1 in men. FVC was accurately predicted by all equations except NHANES III. The discrepancy was even greater among women; the ECSC equation underpredicted both FEV1 and FVC, the NHANES III equation overpredicted both FEV1 and FVC, while the third set of equations accurately predicted FEV1 but overpredicted FVC. The derived reference equation for FEV1 in men was -0.28 age + 0.057 height - 4.91, and in women -0.021 age + 0.039 height - 2.58. The derived reference equation for FVC in men was -0.28 age + 0.071 height - 6.763, and in women -0.019 age + 0.056 height - 5.018. Conclusions: Measured FEV1 and FVC values in a Greek population differed significantly from those predicted using previously published reference equations. The new locally derived spirometry reference equations may be more suitable for evaluation of lung function in everyday practice.