Prediction equations for normal and low lung function from the Health Survey for England

The aim of this study was to derive new spirometric reference equations for the English population, using the 1995/1996 Health Survey for England, a large nationally representative cross-sectional study. The measurements used were the forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) of a sample of 6,053 "healthy" (nonsmokers with no reported diagnosis of asthma or respiratory symptoms) White people aged > or = 16 yrs. Multiple regression analysis, with age and height as predictors, was carried out to estimate prediction equations for mean FEV1, FVC and FEV1/FVC, separately for males and females. A method based on smoothing multiple estimates of the fifth percentiles of residuals was used to derive prediction equations for the lower limit of normal lung function. The new equations fit the current English adult population considerably better than the European Coal and Steel Community equations, and the proportions of people with "low" (below the fifth percentile) lung function are closer to those expected throughout the whole adult age range (16 to > 75 yrs). For the age ranges the studies share in common, the new equations give estimates close to those derived from other nonlinear equations in recent studies. It is, therefore, suggested that these newly developed prediction equations be used for the White English population in both epidemiological studies and clinical practice.