The role of nasal fractional exhaled nitric oxide as an objective parameter independent of nasal airflow resistance in the diagnosis of allergic rhinitis.

OBJECTIVE: Patients with allergic rhinitis (AR) show augmented activity of nitric oxide (NO) metabolism, similar to those in bronchial asthma (BA). We hypothesized that measurements of nasal fractional exhaled NO (FeNO) could be used as an objective marker to detect the presence of AR. Our objective was to clarify the influence of nasal airflow resistance (NAR) on nasal FeNO levels through an exhalation maneuver in symptomatic AR patients. We also examined the diagnostic test validity of the mean nasal FeNO level for disease discrimination by means of a receiver operating characteristic (ROC) curve analysis.

METHODS: Fifty-nine untreated perennial AR patients without BA and 60 healthy controls were enrolled in this retrospective cross-sectional study. The subjective symptoms were recorded and the disease severity was classified according to the Japanese guideline for AR. The oral and nasal FeNO measurements were carried out using a handheld electrochemical analyzer according to the ATS/ERS guidelines. NAR was measured using a rhinomanometer by the anterior method.

RESULTS: The patients in the moderate-to-most severe AR group showed significantly higher levels of oral FeNO compared to the controls. The AR patients in both the mild (n=25) and the moderate-to-most severe (n=34) groups showed significantly higher levels of nasal FeNO compared to the controls (44.1ppb, 54.5ppb, and 26.5ppb, respectively). There was no significant difference in total NAR between the AR patients and the controls. The results of our comparison of nasal FeNO and NAR values of the ipsilateral nasal cavity for each individual indicated no significant correlation between the two-paired parameters. The optimal cut-off point of the mean nasal FeNO level was calculated as 38.5ppb (with 71% sensitivity and 86% specificity) to discriminate the presence of AR.

CONCLUSION: Nasal FeNO measurements can be an objective parameter for the diagnosis and classification of perennial AR in Japanese individuals. Nasal FeNO and NAR appear to be two independent measures that can be used to objectively evaluate nasal functions.