Objective: To compare FEV1 and FVC, calculated using three sets of reference equations (devised by Polgar & Promadhat, Hsu et al. and Mallozi in 1971, 1979 and 1995, respectively), and to determine whether the three are similar in predicting lung function in children and adolescents with distinct body mass indices (BMIs). Methods: The individuals were separated into four groups in accordance with the reference standards of the National Center for Health Statistics: underweight (UW), normal weight (NW), overweight (OW), and obese (OB). All were then submitted to spirometry. Results: We evaluated 122 healthy children and adolescents, aged 7-14 years. The FVC values predicted for NW females and UW males through the use of the Hsu et al. equation were significantly higher than the measured values, as were the FEV1 values for UW females and males predicted via the Polgar & Promadhat and Hsu et al. equations. In NW females, the FEV1 values predicted via the Polgar & Promadhat equation were significantly higher than were the measured values. Conclusions: In individuals with distinct BMIs, the measured FVC and FEV1 values were not equivalent to those predicted via the Polgar & Promadhat and Hsu et al. equations. The same was not true for the Mallozi equations. The BMI was not a relevant factor for the predictive index of these equations; therefore, the Mallozi equations can be used without alteration for children and adolescents with distinct BMIs.

Keywords: Spirometry; Reference values; Body mass index; Child; Adolescent.