WESTPORT, CT (Reuters Health) – British researchers report that exhaled nitric oxide is a marker of eosinophilic inflammation in children with difficult asthma who have received prednisolone therapy. The findings support the hypothesis, they say, that exhaled nitric oxide can serve as a noninvasive measure of airway inflammation in asthmatics.
Dr. Andrew Bush and colleagues from the Royal Brompton Hospital and National Heart and Lung Institute, in London, evaluated endobronchial biopsies from 31 children with difficult asthma, mean age 11.9 years, who had received 2 weeks of prednisolone therapy. The researchers also biopsied seven nonasthmatic children, according to their report in the October 15th issue of the American Journal of Respiratory and Critical Care Medicine.
Among the 17 children who adhered to prednisolone treatment and had biopsies that could be analyzed, there was a significant correlation between the level of exhaled nitric oxide and the eosinophil score (r = 0.54), Dr. Bush's team found.
This relationship was strongest for patients with persistent asthma symptoms after prednisolone therapy. Among these children, exhaled nitric oxide >7 ppb was tied to an increase in eosinophil score. Regardless of symptoms, control subjects and asthmatics with exhaled nitric oxide <7 ppb had eosinophil scores in the nonasthmatic range, the UK investigators say.
They conclude that "measurement of exhaled nitric oxide in [children with persistent asthma] may be helpful in identifying those with ongoing airway eosinophilia, therefore obviating the need for bronchoscopy and endobronchial biopsy."
In an editorial, Dr. Stephen M. Stick from Princess Margaret Hospital for Children, Perth, Australia, states that Dr. Bush and colleagues "provide further evidence in support of the utility of exhaled nitric oxide measurements for monitoring asthma."
However, Dr. Stick says that the mechanisms involved in nitric oxide remain unclear. "With each new study that investigates the potential for measurements of exhaled nitric oxide as a diagnostic tool there appear to be more questions generated about the biology of NO in the airway than there are answers."
"Perhaps by focusing on some of these questions, new therapeutic opportunities might be realized based upon better understanding of the factors that control NO production in the lung," Dr. Stick concludes.
Am J Respir Crit Care Med 2001;164:1335-1336,
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