Development and validation of predictive equations for spirometry in Portuguese children.

Background: There are no data on lung function reference values for Portuguese children, and the contribution from the Portuguese data set in the Global Lung Function Initiative (GLI) is scant.

Objectives: We aimed to estimate new up-to-date reference values for Portuguese children by fitting a multivariable regression model to a general population sample. Further, we intended to assess the external validity of the obtained reference values and to compare them to the GLI reference values.

Methods: A random sample of 858 children from 20 primary schools were screened by health questionnaire, physical examination, and spirometry. Spirometric parameters recorded were FVC, FEV, and FEF. Multiple regression models were used to derive reference equations.

Results: Overall, 481 children, aged between 7 and 12 years, 267 boys (55.5%), were included. Boys had higher values for FVC and FEV than girls ( < .05). The strongest correlation was found for FVC with height ( = 0.71 for boys and 0.70 for girls), while the lowest correlation was observed in both sexes for FEF with age ( = 0.23). Height was the most significant predictor of FVC, FEV, and FEF in our models. Weight and body mass index were not significant predictors for boys but had a significant effect on girls' equations for all spirometry parameters. Compared to obtained reference equations with GLI, they performed better for FVC in boys, FEV in girls, and FEF in both boys and girls.

Conclusion: We offer up-to-date reference values of spirometry for Portuguese children that can be used in clinical practice and research.