IPF pathogenesis is believed to be complex, including epithelial injury, resident fibroblast-myofibroblast transformation, recruitment of fibrocytes, macrophage activation, and release of numerous cytokines and chemokines. Several of these processes release potential biomarker proteins into the blood stream or onto the epithelial surface where they can be measured. Biomarkers have mainly two potential roles in IPF. Firstly, a diagnostic biomarker would distinguish IPF from other diseases with similar symptoms, facilitating diagnosis and possibly decreasing the need for risky procedures, such as surgical lung biopsy. Secondly, a prognostic biomarker would distinguish rapid progressors from slow progressors, which is difficult today.