Prediction of pulmonary restriction from forced vital capacity in elderly is similar using GLI and ERS equations.

ABSTRACT

INTRODUCTION: The prevalence of pulmonary restriction increases in the elderly and detection could be challenging due to the difficulty in measuring lung volumes in older patients. The recently published Global Lung Function Initiative (GLI) equations were found to predict better restriction in middle-aged patients compared to ERS'93 norms. However, the ability of the GLI equations to detect pulmonary restriction in older patients has not been investigated. PATIENTS AND METHODS: We extracted spirometric data in patients older than 85 years from the database of our pulmonary function testing laboratory. The population with pulmonary restriction was defined as those having a total lung capacity value (TLC) below the lower limit of normal (LLN) using ERS'93 equations. We then compared the ability of the ERS'93 and GLI equations to detect this when the forced vital capacity (FVC) was below the LLN. RESULTS: We analyzed data from 285 patients. A true restrictive defect was found in 66 patients (23%). Sensitivity to detect a reduced TLC was higher when calculated from the GLI than the ERS'93 equations, (70 vs 45%). By contrast, specificity was lower (74 vs 89%, respectively); there was no difference in the negative predictive value (89 and 84%). Using receiver operating curves, both sets of equations performed similarly to detect spirometric restriction. CONCLUSIONS: In conclusion, both sets of equations similarly predicted a pulmonary restriction in older subjects. The high negative predictive value of the GLI equations thus allows for static lung volume measurement to be avoided in older patients when the FCV exceeds the LLN whatever the predicted equation used.