Chronic cough is common and often bothersome. Clinical management attempts to recognize the cause and treat the cough. Frequent causes of cough include asthma, smokers’ or infective bronchitis, postnasal drip, gastroesophageal reflux and drugs . Often, however, no cause can be identified, and the patient is given trials of treatment.
A new investigative tool in chronic cough and airway disease is the examination of induced sputum for cells and fluid phase markers of inflammation . Sputum examination was responsible for identifying the occurrence of chronic cough with sputum eosinophilia in patients who did not have the variable airflow limitation of asthma. The cough and eosinophilia were reversed by treatment with an inhaled steroid . Other studies of asthma and chronic airflow limitation suggest that sputum eosinophilia is an important predictor of benefit from steroid treatment. However, sputum eosinophilia appears to be present in only about 10% of patients with nonasthmatic chronic cough.