Can the New Global Lung Initiative Equations Better Stratify the Risk of Death in Elderly People with Chronic Obstructive Pulmonary Disease?

Abstract

Background: The forced expiratory volume in the first second (FEV₁) is commonly expressed as percentage of its value predicted by equations. The most commonly used equations are poorly applicable to elderly people. Recently, a set of equations (Global Lung Initiative, GLI) has been released that is expected to be more appropriate in this population. Objectives: We evaluated the agreement of the GLI, European Respiratory Society (ERS), and National Health and Nutrition Examination Survey (NHANES) equations for prediction of FEV₁ and compared their discriminative capacity with respect to mortality, taking as reference the prediction equation developed in the population from which our sample was drawn (SARA). Methods: We studied 264 patients with chronic obstructive pulmonary disease aged ≥70 years. Agreement was evaluated using the Bland-Altman method, discriminative capacity using incidence rate ratios for mortality calculated across quartiles of each measure. Results: The mean age of the sample was 75.8 years (72.7% men). In women, the mean FEV1ERS/FEV1SARA, FEV1NHANES/ FEV1SARA, and FEV1GLI/FEV1SARA were 0.81, 0.91, and 0.966, respectively. The corresponding values in men were 0.959, 0.963, and 1.02, respectively. The overall discriminative capacity with respect to death was equally poor for all equations. Conclusion: The GLI equations for predicting FEV₁ provide similar estimates compared to an equation developed in a healthy subset of the population in which they are applied, and higher values compared to the ERS equation, especially in women. However, the use of the GLI equation does not improve the stratification of the risk of mortality in elderly people compared to ERS or NHANES equations.