Predictive Equations for Lung Function Based on a Large Occupational Population in North China

Abstract

Objectives: The currently used predictive equations of lung function in North China were derived from early study and have not been updated for nearly two decades. Methods: Using American Thoracic Society (ATS) standards, sex-specific spirometric predictive equations for forced vital capacity (FVC), forced expiratory volume in one second (FEV₁), ratio of FEV₁ to FVC (FEV₁%) and forced expiratory flow at 25-75% of forced vital capacity (FEF_25-75%) were derived from 2,897 asymptomatic, lifelong non-smokers (1,208 males, 1,689 females) from a large occupational population in North China. Stepwise multiple regressions were carried out to identify the best predictors of lung function parameters and predictive equations. Independent variables considered for inclusion in predictive equations including age, height, weight and chest circumference were examined. Results: Age and height were found to be necessary variables for all lung function parameters. Weight was a significant variable in only half of our equations. Chest circumferences (expired or inspired) was excluded as they are not practical in use. Data from 255 apparently healthy non-smokers were used to validate the equations by comparing percentage predicted values and proportion of subjects with normal predicted values with those from the study group, and a high accordance was obtained. Other equations published and used in North China do not appear to offer advantages over these equations. Conclusions: These newly developed predictive equations should ideally be applied to calculate lung function for adult individuals and populations as reference values in North China.