Spirometry reference values for population aged 7-80 years in China

Background and objective: Lung function tests are widely used in clinical and public health practice; however, no valid spirometry reference values were available for the general population in China. This study aimed to provide valid spirometry predictive equations for the general population in China, and to evaluate the predictive performance of previously used equations. Methods: Data from the China National Health Survey 2012-2015 and the 'Generalized Additive Models for Location, Scale and Shape' statistical modelling method were used to establish spirometry predictive equations for forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and FEV1/FVC. Paired t-tests were used to examine differences between spirometry measurements in this sample and predicted values of four previous spirometry predictive equations. Results: This study included 3130 lifetime non-smokers (713 males and 2417 females) aged 7-80 years in China. Spirometry predictive equations with age and height as predictive variables plus age-specific splines were established separately by gender. Most previous spirometry predictive equations were found to significantly overestimate (maximum of 3.69% in FEV1, 1.87% in FVC and 4.19% in FEV1/FVC for males; 11.46% in FEV1, 7.28% in FVC and 3.78% in FEV1/FVC for females) or underestimate (maximum of 5.75% in FEV1 and 8.12% in FVC for males; 7.89% in FEV1 and 9.32% in FVC for females) lung function measurements when applied to this sample population. Conclusion: This study addressed the urgent need for valid and up-to-date spirometry reference values for the general population in China. Moreover, previous spirometry predictive equations showed unfavourable generalizability to this sample population.