Asthma biomarkers in sputum.

Several inflammatory cells are thought to contribute to the pathogenesis of asthma. Among these, the eosinophil appears to be a major effector cell. This review focuses primarily on the clinical utility of sputum eosinophil counts in asthma. Several studies have shown sputum eosinophils to be associated with both asthma severity and level of asthma control. In addition, the presence of sputum eosinophilia is strongly predictive of a favorable response to glucocorticoid therapy. Conversely, the absence of sputum eosinophilia is predictive of a poor response to glucocorticoid therapy. Sputum eosinophilia also predicts asthma relapse in subjects who have their inhaled glucocorticoid reduced or withdrawn. Lastly, inhaled glucocorticoid therapy can be titrated to keep the sputum eosinophil count at or below 2%.