Challenges associated with estimating minimal clinically important differences in COPD-the NHLBI perspective.

Chronic Obstructive Pulmonary Disease (COPD) is a common lung disease that exemplifies the value, as well as the difficulties and challenges, of using minimal clinically important differences (MCID) in clinical research. Development and validation of better endpoints for clinical studies is critical to research progress in COPD. However, the clinical, genetic, and pharmacological heterogeneity of the COPD patient population complicates attempts to define and validate MCIDs for COPD. It is difficult to identify a single measurable outcome that reflects the many components of the COPD patient's health state. Acute exacerbations of symptoms, which COPD patients often experience, present another challenge in the development of MCIDs for this disease. Consequently, the NHLBI does not require the use of MCIDs in clinical research. This allows research on the causes, prevention and diagnosis of COPD and use of endpoints for which an MCID is not yet known. It is important for the scientific community to reach agreement on what is a meaningful MCID in therapeutic trials for COPD. Further research into the concept of the MCID and its application should enable therapeutic trials in COPD to yield knowledge that is more effectively translated into improved public health.