COPD Biomarkers and their interpretation; a Personal perspective

The pathology and impact of COPD results from an abnormal inflammatory process resulting in tissue damage with ineffective repair in response to toxic inhalants (especially cigarette smoke). Identification of mechanisms provides the opportunity to develop new therapies and a personalised approach to management. The collection of multiple genetic and detailed biochemical data from small and large patient cohorts has led to an explosion of studies investigating biomarkers, to achieve these aims. Despite widespread enthusiasm and many statistically significant associations, the interpretation of COPD biomarker results requires thought and leaves many questions unanswered. The current review assesses the importance of these associations, whether they represent cause or effect, reflect disease severity or activity, the complexity of the pathway to the final pathogenic and hence interventional step, and problems interpreting cross sectional studies without knowing individual disease trajectories. The complexity of biomarker specificity without sufficient clinical phenotype and endotype information contributes to problems of interpretation. A strategic change is needed to develop useful COPD biomarkers; this includes focusing on endotype biomarkers within specific clinical phenotypes, biomarkers in the early phases of COPD development that may differ from those in established disease, exacerbation subtype biomarkers, and biomarkers to predict or measure drug effects. Generating these data are critical for the future and multiple potential use/s of biomarkers. At present only blood eosinophils is close to implementation in clinical practice.