Blood and sputum biomarkers in COPD and asthma: a review

Chronic obstructive pulmonary disease (COPD) and asthma are lung inflammatory diseases that represent major public health problems. The primary, and often unique, method to evaluate lung function is spirometry, which reflects disease severity rather than disease activity. Moreover, its measurements strictly depend on patient's compliance, physician's expertise and data interpretation. The limitations of clinical history and pulmonary function tests have encouraged focusing on new possible tracers of diseases. The increase of the inflammatory response in the lungs represents an early pathological event, so biological markers related to inflammation may play key roles in earlier diagnosis, evaluation of functional impairment and prognosis. Biomarkers are measurable indicators associated with the presence and/or severity of a biological or pathogenic process, which may predict functional impairment, prognosis and response to therapy. The traditional approach based on invasive techniques (bronchoalveolar lavage and biopsies) may be replaced, at least in part, by using less invasive methods to collect specimens (sputum and blood), in which biomarkers could be measured. Proteomics, by the association between different protein profiles and pathogenic processes, is gaining an important role in pulmonary medicine allowing a more precise discrimination between patients with different outcomes and response to therapy. The aim of this review was to evaluate the use of biomarkers of airway inflammation in the context of both research and clinical practice.