Abstract
Introduction: Due to the large variation of the predicted values generated by the different equations, it is possible that COPD staging would change when different equations are used.
Objectives: To compare the results of some commonly used spirometry reference equations with the one derived from the PLATINO equation in all patients with COPD from the PLATINO Study; to evaluate the possibility of changing the patient predicted value considering the cut off point as 50% of FEV1 predicted value when the different equations are used
Material and methods: Out of the 5315 individuals evaluated in the PLATINO sample, 759 (52.3% male) of them had COPD according to GOLD criteria. Comparison of staging was performed using the FEV1 in percentage of predicted in each equation, considering the percentage expected from the PLATINO equation as reference.
Results: We evaluated 759 patients with COPD, observing staging changes in 29.4% in relation to the difference equations, being Knudson et al., Crapo et al. and Pereira et al. 2007 equations that showed the greatest number of changes.
Conclusion: Overall these reference equations tested may be applied indistinctly for predicting the spirometry values, although we should reinforce that some of them, like Knudson et al. and Crapo et al., may decrease disease severity, while Pereira et al. 2007 increases the severity, when considering only the percentage of predicted values. These results call to attention the importance of following up patients with COPD by the absolute value of their FEV1 and suggest that only one equation should be used during the treatment of the same patient so as to avoid alterations in the treatment.
- © 2011 ERS