The Stanojevic GLI-2017 regression equations for transfer factor for carbon monoxide arose from the work of a Task Force of the European Respiratory Society. Their report has been endorsed by the European Respiratory Society (ERS).
The aim of the study was to develop The Global Lung Function Initiative (GLI) all-age reference values for TL,CO. Data from 19 centres in 14 countries were collected to define TL,CO reference values. Similar to the GLI spirometry project, reference values were derived using the LMS method and the GAMLSS program in R. A total of 12 660 TL,CO measurements from asymptomatic, lifetime non-smokers were submitted; 85% of the submitted data were from Caucasians. All data were uncorrected for haemoglobin (Hb) concentration. Following adjustments for elevation above sea level, gas concentration, and assumptions used for calculating the anatomic dead space volume, there was a high degree of overlap among the datasets. Reference values for Caucasians aged 5 to 85 years were derived for TL,CO, carbon monoxide transfer coefficient (KCO) and alveolar volume (VA).