Transfer coefficient and static hyperinflation as markers of COPD disease activity: Results from COSYCONET

Patients suffering from chronic obstructive pulmonary disease (COPD) exhibit differential patterns of disease progression. However, biomarkers quantifying disease progression are missing. This study therefore aimed to identify parameters reflecting disease progression and analyse their correlation with medium-term outcome and baseline biomarkers. 1,364 patients from the German COPD cohort COSYCONET were followed for 18 months by evaluating KCO, FEV1, RV/TLC, IC/TLC, SGRQ and exacerbations. The association of these parameters with mortality over the following 3 years, and with baseline levels of leukocytes, CRP, IL-6, IL-8, TNF alpha and fibrinogen was analyzed. Multivariate Cox regression modelling identified a set of five dynamic markers of disease progression over 18-months, each associated with a significant increase of mortality during the next 3 years. Of those, with ~ 52 % and ~ 46 % of patients, respectively, decline in KCO % predicted ≥ 7.5 % and increase in RV/TLC > 2 % were the most frequently observed measures of disease progression. 18-months improvement of disease, however, was most frequently indicated by by reduction of SGRQ > 6 points, occurring in ~ 29 % of patients. Logistic and random forest regression could not predict 18-months activity markers. The authors acknowledge that this study is exploratory in nature and more complex transformation of biomarkers was therefore omitted. Our results suggest KCO % pred. decline to be the most frequent measure of 18-months disease progress in a big cohort of COPD patients.