Nevertheless, our study reflects “real-life” data from two independent German PH referral centres (with a relatively small sample size). We could detect independent associations between fibrinogen plasma concentrations and impaired haemodynamic parameters in CTEPH patients. It is important to note that in our study PAH and CTEPH patients also did not differ regarding the extent of haemodynamic impairment. Therefore, a bias due to different disease severities was minimized, which was often not the case in previous studies.