Furthermore, protein concentrations of PDGF-AA, PDGF-BB, FGF-2, VEGF and M-CSF did not show correlations with demographic (age, sex, race), and baseline lung function characteristics (FVC%, DCLO%, six minute walking distance (6MWD) and ILD-GAP index) between the underlying ILD aetiologies (IPF, SSc-ILD and other ILD) with the exception of a weak correlation of age and FGF-2 (0·37, p < 0·001) for IPF, a correlation of age and PDGF-BB in SSc-ILD (0·59, p = 0·027) and correlations between 6MWD and FGF-2 in other PF-ILD (0·57, p = 0.036). This evidence concerns the gene CSF1 and idiopathic pulmonary fibrosis.