Global lung function initiative 2012 reference values for spirometry in Asian Americans

Background: Spirometry reference values specifically designed for Asian Americans are currently unavailable. The performance of Global Lung Function Initiative 2012 (GLI-2012) equations on assessing spirometry in Asian Americans has not been evaluated. This study aimed to assess the fitness of relevant GLI-2012 equations for spirometry in Asian Americans. Methods: Asian subjects who never smoked and had qualified spirometry data were extracted from the National Health and Nutrition Examination Survey (NHANES) 2011-2012. Z-scores of forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and FEV1/FVC were separately constructed with GLI-2012 equations for North East (NE) Asians, South East (SE) Asians, and individuals of mixed ethnic origin (Mixed). In addition, Proportions of subjects with observed spirometry data below the lower limit of normal (LLN) were also evaluated on each GLI-2012 equation of interest. Results: This study included 567 subjects (250 men and 317 women) aged 6-79 years. Spirometry z-scores (z-FEV1, z-FVC, and z-FEV1/FVC) based on GLI-2012 Mixed equations had mean values close to zero (- 0.278 to - 0.057) and standard deviations close to one (1.001 to 1.128); additionally, 6.0% (95% confidence interval (CI) 3.1-8.9%) and 6.4% (95% CI 3.7-9.1%) of subjects were with observed data below LLN for FEV1/FVC in men and women, respectively. In contrast for NE Asian equations, all mean values of z-FEV1 and z-FVC were smaller than - 0.5; for SE Asian equations, mean values of z-FEV1/FVC were significantly smaller than zero in men (- 0333) and women (-0.440). Conclusions: GLI-2012 equations for individuals of mixed ethnic origin adequately fitted spirometry data in this sample of Asian Americans. Future studies with larger sample sizes are needed to confirm these findings.