Objective measures of asthma control: sputum eosinophils, nitric oxide, and other inflammatory mediators

This discussion concerns the tools we can use to measure the status of inflammation in asthma and therefore help us diagnose and manage this condition. Although measurement of pulmonary function is of course a necessity, it does not necessarily tell us the status of activity of the disease. For example, in a patient with fixed lung obstruction that can occur in asthma, the forced expiratory volume in 1 second (FEV(1)) may be markedly low in the absence of disease activity. In addition, the disease may be highly active in a patient with normal lung functions by virtue of the fact that they are receiving therapy with inhaled corticosteroids and bronchodilators. Finally, measurement of disease activity is useful in establishing a diagnosis of asthma in a patient who is asymptomatic with normal lung functions at the time of presentation. Therefore, tools to measure the status of inflammation would be extremely helpful. In this article two such tools are discussed: the measurement of eosinophilia and the assessment of exhaled nitric oxide.