Impact of the ERS/ATS 2021 standards for lung function interpretation


This study investigates how the recently published ERS/ATS guidelines for lung function interpretation (Stanojevic 2021) affect patient classification compared to the previous document (Pellegrino 2005). 


1323 subjects (244 without and 1079 with a lung condition) who performed a complete PFT at the UZ Leuven (Belgium) are retrospectively analysed. Subjects were Caucasians, over 18 years old, with a majority (59%) with a smoking history and known underlying conditions. Labels for lung function pattern and severity, diffusion pattern and severity and bronchodilator response (BDR) according to both guidelines were generated using interpretative software (ArtiQ.PFT v1.5.0, ArtiQ NV, Belgium). 


The more profound reliance on TLC measurement in the new guidelines resulted in 10% of subjects previously normal becoming restrictive (87% having ILD). The newly created nonspecific pattern was composed of 10% of the subjects who were previously obstructive, where 45% of the group had COPD and asthma s while the rest had other pathologies. Restrictive cases are split into new categories: simple and complex restrictive (69% vs 31%, respectively). The simple restriction was predominantly comprised of ILD subjects (72%), while complex restriction contained neuromuscular diseases and ILD (33%). The newly introduced granularity offers more options to pulmonologists to precisely describe patients’ physiology.  

The use of z-scores to classify severities allows a better consideration of the larger variation within normality in the older population. For obstruction severity, the use of FEV1 z-score rather than %predicted resulted in a milder classification, but no trend was observed for the restrictive cases. 

For the diffusion pattern, no modification was observed except for the rare display of the new elevated diffusion label. The use of DLCO z-score rather than %predicted for diffusion severity was making the 2021 classification outcomes more severe. 

The new BDR equation considers the impact of the low baseline FEV1, resulting in a stringent way to classify the change. Only ten out of 469 previously with insignificant response became significant in the new guidelines. However, newly significant BDR was stricter for 22 out of 83 subjects changing from significant to insignificant response. 


The evolution to a more personal and granular PFT interpretation, considering more appropriate reference values and statistical considerations, can improve clinical practice. The higher precision is synonymous with complexity and may be an opportunity for computerized interpretation systems to help perform and standardize interpretations. They may address human factors thereby decreasing inter-rater variability and improving the quality and consistency of PFT interpretation. 


P. Desbordes1, J. Maes1, F. de Jongh3, K. Sylvester4, C.F. Vogelmeier5, A.T. Dinh-Xuan6, J. Mortensen7, W. Janssens2, M. Topalovic1


[1]  ArtiQ NV, Leuven, BE

[2] Respiratory Medicine, University Hospital Leuven, Chronic Diseases, Metabolism and Ageing, KU Leuven, BE

[3] Medisch Spectrum Twente, Enschede, NL

[4] Respiratory Physiology, Royal Papworth Hospital NHS Foundation Trust, Cambridge, UK

[5] Department of Medicine, Pulmonary and Critical Care Medicine, University Medical Center Giessen and Marburg, Marburg, DE, and member of the German Center for Lung Research (DZL)

[6] Service de Physiologie-Explorations Fonctionnelles, Assistance Publique-Hôpitaux de Paris (APHP). Centre, Hôpital Cochin, Université Paris Cité, Paris, FR

[7] Department of Clinical Physiology and Nuclear Medicine, Copenhagen University Hospital, Rigshospitalet, Copenhagen, DK, and Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, DK