Evaluation of the Global Lung Function Initiative reference equations in Belgian adults

Area of Science:

• Pulmonary Medicine
• Respiratory Physiology

Background:

• The Global Lung Function Initiative (GLI) Network has established reference equations for spirometry, diffusing capacity of the lung for carbon monoxide (DLCO), and lung volumes.
• These equations are intended for all age groups.

Purpose of the Study:

• To evaluate the appropriateness of GLI reference equations in an adult Caucasian population in Belgium.
• To assess potential misclassification of respiratory conditions due to equation fit and proposed limits.

Main Methods:

• Retrospective analysis of lung function data from 1311 healthy, non-smoking, non-obese adults (18-88 years) who underwent tests before sleep investigations.
• Multiple linear regression analysis was used to assess lung function z-scores in relation to height, age, and sleep apnea status.

Main Results:

• GLI equations showed an adequate fit for static lung volumes and DLCO in the studied population.
• Lung function z-scores were dependent on height and age, with inverse associations observed for FEV1/FVC with height and DLCO with height (males) and age (females).
• Fewer than 5% of subjects fell below the GLI-proposed lower limit of normal (LLN), suggesting the LLN may be too low.

Conclusions:

• GLI reference equations are generally adequate for Belgian adults, but the proposed LLN may result in underdiagnosis of lung disease.
• Height and age associations with lung function indices necessitate careful consideration to avoid misclassification of airway obstruction and diffusion disorders.