Exhaled Nitric Oxide and its role in the treatment of Asthma - Part I

In a series of discussions substantiated by findings and excerpts from reputed medical journals and scientists, we strive to understand the importance of exhaled nitric oxide and its role in the treatment of asthma.

In the first part of the series, we discuss the findings from the reputed New England Journal of Medicine on Use of Exhaled Nitric Oxide Measurements to Guide Treatment in Chronic Asthma.

In medicine, exhaled nitric oxide (eNO) can be measured in a breath test for asthma which is characterized by airway inflammation. Nitric oxide (NO) is a gaseous molecule produced by certain cell types in an inflammatory response. Exhaled NO (also referred to as FENO) is a promising biomarker as a guide to therapy in adults and children with asthma. The breath test has recently become available in many well-equipped hospitals in developed countries. Clinical trials have looked at whether tailoring asthma therapy based on eNO values is better than conventional care, in which therapy is gauged by symptoms and the results of lung function tests.

An excerpt from the New England Journal of Medicine in a study by Andrew D. Smith, M.B., Ch.B., Jan O. Cowan, Karen P. Brassett, G. Peter Herbison, M.Sc., and D. Robin Taylor, M.D. details the trial to establish the use of eNO in the measurements to guide treatment in chronic asthma.

The findings of the study are detailed below.

Background

International guidelines for the treatment of asthma recommend adjusting the dose of inhaled corticosteroids on the basis of symptoms, bronchodilator requirements, and the results of pulmonary-function tests. Measurements of the fraction of exhaled nitric oxide (FeNO) constitute a noninvasive marker that may be a useful alternative for the adjustment of inhaled-corticosteroid treatment.

Methods

In a single-blind, placebo-controlled trial, the investigators randomly assigned  97 patients with asthma who had been regularly receiving treatment with inhaled corticosteroids to have their corticosteroid dose adjusted, in a stepwise fashion, on the basis of either FeNO measurements or an algorithm based on conventional guidelines. After the optimal dose was determined (phase 1), patients were followed up for 12 months (phase 2). The primary outcome was the frequency of exacerbations of asthma; the secondary outcome was the mean daily dose of inhaled corticosteroid.

Results

Forty-six patients in the FeNO group and 48 in the group whose asthma was treated according to conventional guidelines (the control group) completed the study. The final mean daily doses of fluticasone, the inhaled corticosteroid that was used, were 370 ?g per day for the FeNO group (95 percent confidence interval, 263 to 477) and 641 ?g per day for the control group (95 percent confidence interval, 526 to 756; P=0.003), a difference of 270 ?g per day (95 percent confidence interval, 112 to 430). The rates of exacerbation were 0.49 episode per patient per year in the FeNO group (95 percent confidence interval, 0.20 to 0.78) and 0.90 in the control group (95 percent confidence interval, 0.31 to 1.49), representing a non-significant reduction of 45.6 percent (95 percent confidence interval for mean difference, ¡78.6 percent to 54.5 percent) in the FeNO group. There were no significant differences in other markers of asthma control, use of oral prednisone, pulmonary function, or levels of airway inflammation (sputum eosinophils).

Conclusions

With the use of FeNO measurements, maintenance doses of inhaled corticosteroids may be significantly reduced without compromising asthma control.