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Exhaled Nitric Oxide May Serve as Asthma Measure


 

WASHINGTON — Measures of exhaled nitric oxide levels may add another dimension to the evaluation of asthma beyond the information available from the Asthma Control Test and spirometry findings, 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 and cystic fibrosis.

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. The lack of correlation held true when the patients were divided into four groups based on severity.

The FeNO measures in patients with intermittent asthma, mild persistent asthma, moderate persistent asthma, and severe persistent asthma were 20.4 ppb, 29.3 ppb, 25.9 ppb, and 39.7 ppb, respectively. The ACT scores in these groups were 22.2, 20.0, 19.7, and 17.1, respectively. The FEV1 scores were 103%, 95.1%, 90.4%, and 70.4%, respectively, and the FEV1/FVC scores were 93.3%, 90.7%, 91.2%, and 79.0%, respectively.

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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