Prediction equations for forced spirometry from European origin populations

The objective of this study was the analysis of five sets of reference equations for forced spirometry (Crapo et al., ECSC, Knudson et al., Paoletti et al. and Roca et al.) using measurements of FVC and FEV, obtained in the European Community Respiratory Health Survey (ECRHS) in Spain. Standardized forced spirometry was measured in 998 non-asthmatic subjects (20-44 years), randomly selected from the general population, participating in the ECRHS in four different Spanish cities. Observed minus predicted values for both FVC and FEV, were examined for each set of predicted equations. Observed FVC (4448 +/- 980 ml) and FEV1 (3715 +/- 813 ml) showed a good agreement with values predicted by Roca et al. (99% and 101%, respectively). The mean observed minus predicted difference (residual) for FVC and FEV1 were -34 +/- 527 ml and 30 +/- 455 ml, respectively. The regression line between observed and predicted values was not different from the identity line for both FVC and FEV1. These results indicate that reference values obtained by Roca et al. are useful for the assessment of the ventilatory capacity in the general population of Spain. In addition, the study indicates that discrepancies among the reference equations from different authors compared in the present study are unlikely to be due to ethnic differences within European origin populations.