These contradicting reports might be the consequence of different inclusion criteria and/or severity of the disease in tested CPFE patients, since KL-6 and SP-D, and in particular their combined product (KL-6 × SP-D), were found to be good indicators for an estimation of the degree of fibrosis in CPFE [68]. This evidence concerns the gene MUC1 and combined pulmonary fibrosis-emphysema syndrome.