Cross-sectional and Longitudinal Spirometry in Children and Adolescents Interpretative Strategies

Rationale: Single and serial spirometric data are commonly compared with predicted values to assess pulmonary function and normal lung growth.Objectives: Do reference equations adequately describe pulmonary function in a population and in growing individuals?Methods: We applied five sets of reference equations with appropriate age ranges to cross-sectional data of FEV1, FVC, and FEV1/FVC from the United States, Estonia, and The Netherlands (1,487 boys and 1,340 girls, 6 to 18 years of age), and to serial measurements in Dutch (430 girls and 769 boys, 6 to 19 years of age) and in German and Austrian children (1,305 girls and 1,303 boys, 6 to 13 years of age).Measurements and Main Results: Compared with reference equations from Polgar and Zapletal, cross-sectional FEV1 and FVC declined between the ages of 6 and 12 and then increased, leading to a spurious change of up to 25% predicted; this pattern was most pronounced in boys. In cross-sectional data this trend was much weaker when using reference equations...