Objective: To compare the most recent (2006) predicted values of forced vital capacity and forced expiratory volume in one second for spirometry in Brazilians with those obtained using other reference equations and to validate the findings through comparisons with a new sample of normal Brazilians.
Methods: Forced spirometry was performed, in accordance with the Brazilian Thoracic Society guidelines, in 643 nonsmoking adult Caucasians. The predicted values obtained by Brazilian researchers in 1992 and those obtained by four groups of foreign researchers were compared with the new Brazilian predicted values obtained in 2006. In the second phase, the mean values obtained in 65 adult females and 79 adult males were compared with the predicted values obtained using the various reference equations.
Results: A t-test for paired samples revealed significant differences between the predicted values obtained using the six equations and those obtained using the 2006 Brazilian equation. In the second phase, the mean predicted values obtained by Crapo et al., as well as those obtained by Hankinson et al. for Mexican-Americans, were similar to those found in the new sample. However, when the predicted values obtained in the new sample were compared with those obtained by those authors, discrepancies were found, with high and low predicted values. The mean values obtained using the 2006 Brazilian equation presented the smallest differences in comparison with the mean values obtained in the new sample.
Conclusions: These results underscore the importance of using prediction equations for spirometry that are appropriate for our population.