WASHINGTON — Measures of exhaled nitric oxide levels may add another dimension to the evaluation of asthma, based on data from a study presented at the annual meeting of the American Academy of Allergy, Asthma, and Immunology.
Fractional exhaled nitric oxide (FeNO) may be “a surrogate marker for airway inflammation,” Dr. Brian C. Schroer of the Cleveland Clinic said in an interview. Neither the Asthma Control Test (ACT) nor spirometry evaluate airway inflammation.
Dr. Schroer and his colleagues reviewed charts from the asthma-related medical visits of 139 adults, all of whom concurrently completed the ACT, FeNO, and spirometry tests. Approximately 66% of the patients were female, and 78% were white. The study excluded smokers and patients with concomitant conditions including chronic obstructive pulmonary disease, cystic fibrosis, and hypereosinophilic syndrome.
Overall, the average FeNO score was 30.8 parts per billion (ppb), the average ACT score was 19.2, the average forced expiratory volume in 1 second (FEV1) score was 86.5%, and the average FEV1/forced vital capacity (FVC) score was 87.4%. Scatter plots showed no correlation between FeNO and either ACT or spirometry measures.
Dr. Schroer said that he was initially surprised by the finding that inflammation was not increased in patients whose ACT scores were either decreased or normal. But the ACT doesn't take airway inflammation into account, and spirometry measures only airway hyperresponsiveness, he said, “so it doesn't surprise me in the long run that the airway inflammation isn't correlated with these other measurements of asthma control.”
The lack of correlation held true when the patients were divided into four groups based on asthma severity.
The study was supported by the William O. Wagner, M.D., Research and Education Fund. Dr. Schroer had no financial conflicts to disclose.
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