Using post-bronchodilator FEV₁ is better than pre-bronchodilator FEV₁ in evaluation of COPD severity.

Background: The current standards for the diagnosis and treatment of patients with COPD clearly rely on the Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria based on post-bronchodilator spirometric values. However, clinical evidence for using the post-bronchodilator FEV₁ in the severity classification has not been fully investigated.

Methods: Patients with COPD were enrolled and followed up prospectively between October 2006 and January 2011. We compared the observed 3-year risk of all causes and respiratory mortality with the risk predicted by the pre- and post-bronchodilator percent predicted FEV₁. Other important phenotypes including BMI, MMRC dyspnea scale, ECOG performance status and severe AECOPD (acute exacerbation) were also compared between the two groups. The different severity classifications of COPD, measured according the GOLD guidelines by post- and pre-bronchodilator percent predicted FEV₁ were compared for prediction of mortality.

Results: There were 35 deaths among the 300 COPD patients (11.7%). Multivariate analysis showed that the post-bronchodilator percent predicted FEV₁ was a significant independent predictor of mortality but pre-bronchodilator percent predicted FEV₁ was not (p = 0.008 vs 0.126) and it was more strongly correlated with all studied predictors of outcome than the pre-bronchodilator percent predicted FEV₁. Kaplan-Meier analysis showed that the discrimination ability to predict mortality from the GOLD criteria using post bronchodilator percent predicted FEV₁ (p = 0.009) was better than using pre-bronchodilator percent predicted FEV₁ (p = 0.131).

Conclusions: The post-bronchodilator percent predicted FEV1 is better than the pre-bronchodilator percent predicted FEV₁ in the evaluation of the severity of disease in COPD patients and is more accurate in predicting the risk of death by the GOLD classification.