Usefulness of exhaled nitric oxide for diagnosing asthma

J Asthma. 2010 Sep;47(7):817-21. doi: 10.3109/02770903.2010.491147.


Rationale: A standard asthma diagnosis is made based on clinical history, reversibility of airway obstruction, and bronchial hyperresponsiveness. Fractional exhaled nitric oxide (FeNO) is a noninvasive airway inflammatory marker that has been suggested as a diagnostic tool for asthma. The aim of this study was to establish a FeNO cut-off value for asthma diagnosis.

Methods: One hundred and fourteen consecutive adult patients (mean age 34 ± 13 years) reporting symptoms consistent with asthma, with normal spirometric parameters and a negative bronchodilator test, were included in the study. All underwent a methacholine challenge test following the five-breath dosimeter protocol. FeNO was measured with a portable device (NioxMino, Aerocrine AB, Sweden) just before the methacholine challenge. The sensitivity, specificity, and diagnostic performance of FeNO measurement were calculated.

Results: Thirty-five out of the 114 patients (30.7%) were diagnosed with asthma. A positive methacholine challenge was associated with higher FeNO levels and with lower forced expiratory volume in one second (FEV(1)) at baseline. No correlation was found between methacholine provocative concentration causing a decrease of 20% in FEV(1) (PC(20)) and FeNO levels. A receiver-operating characteristic curve was constructed for FeNO levels (area under the curve [AUC]: 0.762; 95% confidence interval [CI]: 0.667-0.857; p < .001). The FeNO cut-off point with maximal specificity and sensitivity for asthma diagnosis was 40 ppb.

Conclusions: Patients with confirmed asthma showed higher FeNO levels. A cut-off value of 40 ppb was calculated as the most efficient for asthma diagnosis in our population. The use of FeNO measurement may be a helpful tool to rule out a diagnosis of asthma, especially in patients in whom a methacholine challenge is not feasible or available.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Asthma / diagnosis*
  • Asthma / physiopathology
  • Breath Tests*
  • Exhalation
  • Female
  • Forced Expiratory Volume
  • Humans
  • Male
  • Middle Aged
  • Nitric Oxide / analysis*
  • ROC Curve


  • Nitric Oxide