Abstract
BACKGROUND: Sputum eosinophil counts and exhaled nitric oxide (NO) levels are increased in asthma and both measurements fall in response to corticosteroids. METHODS: Exhaled NO levels and sputum eosinophil counts were assessed as non-invasive markers of the response to an oral steroid in 37 patients (19 women) with stable chronic asthma (mean (SD) age 48.6 (12.2) years, asthma duration 25. 9 (17.3) years, and baseline forced expiratory volume in one second (FEV(1)) 76.3 (21.9)% predicted). Spirometric tests, with reversibility to a beta agonist (2.5 mg nebulised salbutamol), and induced sputum (using nebulised 3% saline) were performed at recruitment and following treatment with 30 mg prednisolone/day for 14 days. RESULTS: Baseline NO levels correlated with the percentage improvement in FEV(1) from baseline to the post-steroid, post-bronchodilator value (r(s) = 0.47, p = 0.003), with an NO level of >10 ppb at baseline having a positive predictive value of 83% for an improvement in FEV(1) of > or =15% (sensitivity 59%, specificity 90%). Sputum eosinophilia (> or =4%) had a positive predictive value of 68% (sensitivity 54%, specificity 76%) for an increase in FEV(1) of > or =15%. A combination of sputum eosinophilia and increased NO levels resulted in a positive predictive value of 72% and a negative predictive value of 79% (sensitivity 76%, specificity 75%). CONCLUSION: Exhaled NO levels and sputum eosinophilia may be useful in predicting the response to a trial of oral steroid in asthma.