Spirometric reference values for children and adolescents from Kazakhstan.

Background: Spirometric parameters are influenced by several factors and many reference data are available in the literature. However, no spirometric data are available for children and adolescents from Central Asia.
Aim: The study aimed to calculate spirometric reference curves on the basis of anthropometry, ethnicity (Kazakh vs. Russian) and living environment (urban vs. rural).
Subjects and Methods: Spirometry (FEV1, FVC and FEF25-75%) was performed and anthropometric measurements taken for 1926 male and 1967 female Kazakh children aged 7-18 years.
Results: Height explained almost all the variance of forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) for both sexes, while age and inspiratory circumference contributed slightly to the prediction. Moreover, FVC and FEV1 were greater in Russians than in Kazakhs and ethnicity did enter the prediction model for these parameters. The living environment had a marginal effect on spirometry. In fact, forced expiratory flow 25-75% (FEF25-75%) was slightly higher in urban than in rural females, FVC was slightly higher in rural than in urban males, while FEV1 was not affected. Finally, among several spirometric equations available in the literature, those performing better in our children were obtained in developed countries.
Conclusion: Anthropometry was the most important predictor of spirometry. Age and ethnicity were also predictors, while the contribution of the living environment was more limited.