The expanding role of biomarkers in the assessment of smoking-related parenchymal lung diseases.

Recent advances in the field of clinical biomarkers suggest that quantification of serum proteins could play an important role in the diagnosis, classification, prognosis, and treatment response of smoking-related parenchymal lung diseases. COPD and idiopathic pulmonary fibrosis (IPF), two common chronic progressive parenchymal lung diseases, share cigarette smoke exposure as a common dominant risk factor for their development. We have recently shown that COPD and interstitial lung disease may represent distinct outcomes of chronic tobacco use, whereas others have demonstrated that both diseases coexist in some individuals. In this perspective, we examine the potential role of peripheral blood biomarkers in predicting which individuals will develop COPD or IPF, as well as their usefulness in tracking disease progression and exacerbations. Additionally, given the current lack of sensitive and effective metrics to determine an individual's response to treatment, we evaluate the potential role of biomarkers as surrogate markers of clinical outcomes. Finally, we examine the possibility that changes in levels of select protein biomarkers can provide mechanistic insight into the common origins and unique individual susceptibilities that lead to the development of smoking-related parenchymal lung diseases. This discussion is framed by a consideration of the properties of ideal biomarkers for different clinical and research purposes and the best uses for those biomarkers that have already been proposed and investigated.