Korean J Asthma Allergy Clin Immunol.  2012 Jun;32(2):83-91.

Usefulness of Fractional Exhaled Nitric Oxide for the Diagnosis of Asthma and Its Assessment of Asthma Control

Abstract

BACKGROUND
Fractional exhaled nitric oxide (FeNO) tests may detect eosinophilic airway inflammation in asthmatic patients and are known to be simple, easy and less time-consuming. However, there have been few studies on the usefulness of FeNO tests for the diagnosis and management of asthma in Korea.
METHODS
One hundred and sixty-one patients with asthmalike symptoms, such as episodic breathlessness, wheezing, cough and/or chest tightness, were included. Tests for FeNO and induced sputum were performed. Asthma was diagnosed if a subject had a positive airway hyperresponsiveness to methacholine or a significant reversible airflow obstruction. Levels of asthma control were classified according to the Expert Panel Report 3 guideline.
RESULTS
The numbers of asthmatics and non-asthmatics were 90 and 71, respectively. FeNO levels positively correlated with sputum eosinophils. The area under the curve (AUC) from receiver operating characteristic curve of FeNO for asthma diagnosis was 0.686 (95% confidence interval [CI], 0.604~0.767) and the optimal cutoff point was 25.5 ppb, which gave a sensitivity of 57.1%, a specificity of 75.7%, a positive predictive value (PPV) of 75.4% and a negative predictive value (NPV) of 57.6%. The AUC of FeNO for the determination of uncontrolled asthma was 0.812 (95% CI, 0.718~0.906) and the optimal cutoff point was 24.5 ppb, which gave a sensitivity of 76.6%, a specificity of 80.8%, PPV of 90.7% and an NPV of 58.3%.
CONCLUSION
FeNO tests may be useful for diagnosing asthma and for assessing the level of asthma control, with good specificities and positive predictive values.

MeSH Terms

Area Under Curve
Asthma
Cough
Eosinophils
Humans
Inflammation
Methacholine Chloride
Nitric Oxide
Respiratory Sounds
ROC Curve
Sensitivity and Specificity
Sputum
Thorax
Methacholine Chloride
Nitric Oxide