Systemic biomarkers in the evaluation and management of COPD patients: are we getting closer to clinical application?

Chronic obstructive pulmonary disease (COPD) is a complex, multicomponent disease at the clinical, cellular, and molecular levels. Over the past few years there has been a growing interest in the field of biomarkers in COPD and a large number of studies have evaluated potential candidate molecules in different patient settings. Data on systemic biomarkers from large cohorts, including the well-characterized population of the ECLIPSE study, are now available and provide exciting information on the association of biomarkers with clinically important outcomes, including exacerbations, hospitalizations and mortality. Moreover, recent research has provided proof for the existence of distinct "systemic inflammatory" phenotypes. This review summarizes the currently available evidence on systemic biomarkers in COPD, providing clinically relevant information on the possible role of systemic biomarkers in the evaluation of disease activity and severity, phenotypes, outcomes, COPD exacerbations and treatment response and guidance. Despite the fact that no single biomarker is currently ready to characterize sufficiently the status of COPD patients, guide treatment options, and predict future events, recent studies have rendered our current knowledge definitely more advanced than a few years ago and the possible use of biomarkers in the diagnosis and management of COPD patients looks even more promising.