Noninvasive markers of airway inflammation in asthma

Although airway inflammation plays a major role in the pathophysiology of asthma, quantitative markers of airway inflammation are limited in clinical practice.

To determine if levels of noninvasive markers of eosinophil-catalyzed oxidation, lipid peroxidation, and nitric oxide production are associated with asthma.

Participants were enrolled from academic medical centers participating in the Severe Asthma Research Program. Clinical characteristics, laboratory data, pulmonary function tests, and levels of the following noninvasive markers were obtained: urinary bromotyrosine, a marker of eosinophil-catalyzed oxidation; urinary F(2)-isoprostanes, markers of lipid peroxidation; and exhaled nitric oxide, a marker of airway inflammation

Fifty-seven asthmatic participants and thirty-eight healthy participants were enrolled. Bromotyrosine, F(2)-isoprostanes, and exhaled nitric oxide were each significantly increased in asthmatic participants versus controls (p<0.01). An elevated level (greater than median) of any marker was associated with a significant 3- to 6-fold greater odds of having asthma. Participants with two or more elevated marker levels showed an 18-fold greater odds of having asthma. Relationships were also noted with airflow obstruction and bronchodilator response.

Findings from this pilot study indicate that urinary levels of bromotyrosine and F(2)-isoprostanes, in addition to exhaled nitric oxide levels, are associated with asthma.