Implications of the 2022 lung function update and GLI global reference equations among patients with interstitial lung disease

• Published in: Thorax Vol. 79; no. 11; pp. 1024 - 1032
• Main Authors: Li, Andrew, Teoh, Alan, Troy, Lauren, Glaspole, Ian, Wilsher, Margaret L, de Boer, Sally, Wrobel, Jeremy, Moodley, Yuben P, Thien, Francis, Gallagher, Henry, Galbraith, Michelle, Chambers, Daniel C, Mackintosh, John, Goh, Nicole, Khor, Yet Hong, Edwards, Adrienne, Royals, Karen, Grainge, Christopher, Kwan, Benjamin, Keir, Gregory J, Ong, Chong, Reynolds, Paul N, Veitch, Elizabeth, Chai, Gin Tsen, Ng, Ziqin, Tan, Geak Poh, Jackson, Dan, Corte, Tamera, Jo, Helen
• Format: Journal Article
• Language: English
• Published: England BMJ Publishing Group Ltd and British Thoracic Society 24.09.2024; BMJ Publishing Group LTD; BMJ Publishing Group
• Subjects: Aged; Carbon monoxide; Classification; Clinical trials; Connective tissue disease associated lung disease; Ethnicity; Female; Forced Expiratory Volume - physiology; Humans; Idiopathic pulmonary fibrosis; Interstitial Fibrosis; Interstitial Lung Disease; Lung diseases; Lung Diseases, Interstitial - physiopathology; Lungs; Male; Middle Aged; Mortality; Original Research; Pulmonary vasculitis; Rare lung diseases; Reference Values; Registries; Respiratory Function Tests; Variables; Vital Capacity - physiology; Interstitial Fibrosis; Connective tissue disease associated lung disease; Rare lung diseases; Pulmonary vasculitis; Idiopathic pulmonary fibrosis
• ISSN: 0040-6376; 1468-3296; 1468-3296
• DOI: 10.1136/thorax-2024-221813

BackgroundLung function testing remains a cornerstone in the assessment and management of interstitial lung disease (ILD) patients. The clinical implications of the Global Lung function Initiative (GLI) reference equations and the updated interpretation strategies remain uncertain.MethodsAdult patients with ILD with baseline forced vital capacity (FVC) were included from the Australasian ILD registry and the National Healthcare Group ILD registry, Singapore.The European Coal and Steel Community and Miller reference equations were compared with the GLI reference equations to assess (a) differences in lung function percent predicted values; (b) ILD risk prediction models and (c) eligibility for ILD clinical trial enrolment.ResultsAmong 2219 patients with ILD, 1712 (77.2%) were white individuals. Idiopathic pulmonary fibrosis (IPF), connective tissue disease-associated ILD and unclassifiable ILD predominated.Median FVC was 2.60 (2.01–3.36) L, forced expiratory volume in 1 s was 2.09 (1.67–2.66) L and diffusing capacity of the lungs for carbon monoxide (DLCO) was 13.60 (10.16–17.60) mL/min/mm Hg. When applying the GLI reference equations, the mean FVC percentage predicted was 8.8% lower (87.7% vs 78.9%, p<0.01) while the mean DLCO percentage predicted was 4.9% higher (58.5% vs 63.4%, p<0.01). There was a decrease in 19 IPF and 119 non-IPF patients who qualified for the nintedanib clinical trials when the GLI reference equations were applied. Risk prediction models performed similarly in predicting mortality using both reference equations.ConclusionApplying the GLI reference equations in patients with ILD leads to higher DLCO percentage predicted values and smaller lung volume percentage predicted values. While applying the GLI reference equations did not impact on prognostication, fewer patients met the clinical trial criteria for antifibrotic agents.