Asthma end points and outcomes: what have we learned?

In spite of the wide prevalence of asthma and its substantial consequences, the diagnosis and assessment of asthma has not been standardized, and the goals of therapy currently are not being achieved. Our purpose is to help delineate what the most important asthma end points are and what kinds of strategies we should use to guide therapy. Comparison of numerous studies reveals that asthma measures used routinely in the clinic, such as spirometric lung function, do not uniformly correlate with asthma control. We cannot improve outcomes until we determine which measures reveal the underlying disease process most clearly and at the same time offer ease of performance during routine office visits. We propose that by standardizing the way we collect and analyze data from our daily practice, we can better define which measures reflect true asthma control. Such measures most likely address a spectrum of changes occurring in the pathophysiology of asthma, notably distal airway inflammation and hyperresponsiveness. Inflammation may provide the best opportunity for assessment and treatment, because if it is adequately addressed, airway sensitivity may improve, thereby reducing airway obstruction and subsequently minimizing exacerbations. The fraction of exhaled nitric oxide as a measure of inflammation is suggested as offering the best combination of disease evaluation and practical implementation for improved asthma outcomes.