Use of exhaled nitric oxide measurement to identify a reactive, at-risk phenotype among patients with asthma.
BACKGROUND
Exhaled nitric oxide (Fe(NO)) is a biomarker of airway inflammation in mild to moderate asthma. However, whether Fe(NO) levels are informative regarding airway inflammation in patients with severe asthma, who are refractory to conventional treatment, is unknown. Here, we hypothesized that classification of severe asthma based on airway inflammation as defined by Fe(NO) levels would identify a more reactive, at-risk asthma phenotype.


METHODS
Fe(NO) and major features of asthma, including airway inflammation, airflow limitation, hyperinflation, hyperresponsiveness, and atopy, were determined in 446 individuals with various degrees of asthma severity (175 severe, 271 non-severe) and 49 healthy subjects enrolled in the Severe Asthma Research Program.


RESULTS
Fe(NO) levels were similar among patients with severe and non-severe asthma. The proportion of individuals with high Fe(NO) levels (>35 ppb) was the same (40%) among groups despite greater corticosteroid therapy in severe asthma. All patients with asthma and high Fe(NO) had more airway reactivity (maximal reversal in response to bronchodilator administration and by methacholine challenge), more evidence of allergic airway inflammation (sputum eosinophils), more evidence of atopy (positive skin tests, higher serum IgE and blood eosinophils), and more hyperinflation, but decreased awareness of their symptoms. High Fe(NO) identified those patients with severe asthma characterized by the greatest airflow obstruction and hyperinflation and most frequent use of emergency care.


CONCLUSIONS
Grouping of asthma by Fe(NO) provides an independent classification of asthma severity, and among patients with severe asthma identifies the most reactive and worrisome asthma phenotype.
Department of Pulmonary, Allergy, and Critical Care Medicine/Respiratory Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA. dweikr@ccf.org
Raed A
RA
Dweik
Ronald L
RL
Sorkness
Sally
S
Wenzel
Jeffrey
J
Hammel
Douglas
D
Curran-Everett
Suzy A A
SA
Comhair
Eugene
E
Bleecker
William
W
Busse
William J
WJ
Calhoun
Mario
M
Castro
Kian Fan
KF
Chung
Elliot
E
Israel
Nizar
N
Jarjour
Wendy
W
Moore
Stephen
S
Peters
Gerald
G
Teague
Benjamin
B
Gaston
Serpil C
SC
Erzurum
D000305:Adrenal Cortex Hormones / Q000627:therapeutic use; D000328:Adult; D001249:Asthma / Q000175:diagnosis* / Q000188:drug therapy / Q000378:metabolism / Q000503:physiopathology; D015415:Biomarkers / Q000032:analysis; D001944:Breath Tests; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D016015:Logistic Models; D008297:Male; D015999:Multivariate Analysis; D009569:Nitric Oxide / Q000032:analysis* / Q000378:metabolism; D010641:Phenotype; D012129:Respiratory Function Tests; D012720:Severity of Illness Index; D012882:Skin Tests
D000305:Adrenal Cortex Hormones; D015415:Biomarkers; D009569:Nitric Oxide