In addition, Analysis of Variances (ANOVA) revealed a gradually increasing association between WHO functional class and fibrinogen concentrations in CTEPH (WHO FC II 3.3 ± 0.4, WHO FC III 4.3 ± 0.2; WHO FC IV 5.7 ± 0.5 g/l, p = 0.0172) but not in PAH patients (Fig. 1C+D).