Danish lung function reference values for adults - the DALFUMAT study

<bold>Objectives:</bold> This study aimed to create national reference values for CO diffusing capacity, and dynamic and static lung volumes measured on the same participants, and to compare these to ECCS and GLI standards. Additional aims were to develop lung function reference values based on arm span, establish post-bronchodilator reference values for spirometry, create reference values for bronchodilator response, and identify significant bronchodilator responses based on z-scores. <bold>Methods:</bold> Spirometry, body plethysmography, single-breath diffusion capacity and bronchodilator testing were performed on 908 healthy non-smokers aged 18-97 years, selected from the municipalities of the 13 participating Danish centers. Strict quality control was ensured according to ATS/ERS standards. Sex, age, age², weight, and height (or arm span) were used as independent variables in the multiple regression equations created. The lung function data were compared to the predicted values from GLI and ECCS. <bold>Results:</bold> Sex-specific reference equations were established for 29 lung function parameters. Additionally, reference values based on arm span, post-bronchodilator spirometry, and bronchodilator response were established using four different end-points including z-scores. About half of the new reference values differed clinically significantly (>±0.5 z-score) from the reference values predicted by the GLI and ECCS equations, with this discrepancy being more frequent in females, for ECCS, and for flow and volumes. <bold>Conclusion:</bold> Given that a significant portion of the new reference values differ clinically significantly from the reference values from GLI and ECCS, we recommend the nationwide adoption of the new DALFUMAT reference values.