Assessment tools for chronic obstructive pulmonary disease: do newer metrics allow for disease modification?

The change in FEV1 has been the traditional metric used to define the progression of chronic obstructive pulmonary disease in affected patients. Consequently, various treatments have "targeted" the accelerated decline in FEV1 in an attempt to modify or alter the disease process. We propose a broader definition for "disease modification" as any change in a metric related to the disease that is maintained over time. Available longitudinal and/or predictive data on several newer modalities are described that might be considered as alternative metrics to assess disease modification in chronic obstructive pulmonary disease. These include inspiratory capacity, exercise capacity, the 6-minute walk distance, dyspnea measures, health status, multidimensional indices, and acute exacerbations. Finally, we consider the impact of disease modifying therapies on some of these metrics.