Non-invasive biomarkers in pulmonary fibrosis.

The practise of modern medicine is unthinkable without biological markers, and their adoption is now established in various clinical settings. Pulmonary fibrosis occurs in a heterogeneous group of diseases. IPF is the most frequent fibrotic lung disease and has a poor prognosis. Despite the heterogeneity in underlying diseases multiple common mechanism resulting in pulmonary fibrosis are documented. In this context, several biomarkers for pulmonary fibrosis have been described. Some substances are produced by alveolar epithelial cells such as surfactant proteins A and D, the glycoprotein Krebs von den Lungen 6 Antigen, while others are derived from macrophages such as CCL18. Most recently, increased fibrocyte counts were proposed as a marker of acute exacerbation in IPF. None of these markers is established in clinical practise so far. Studies regarding the clinical value of biomarkers in pulmonary fibrosis are hampered by the fact that fibrotic lung diseases are uncommon and variable in course. However, some markers are clearly promising, and as a spin-off the analysis of some of these in samples from recently finished pharmacological multicentric studies might give urgently needed information regarding their clinical value.