Characterization of the severe asthma phenotype by the National Heart, Lung, and Blood Institute's Severe Asthma Research Program.
BACKGROUND
Severe asthma causes the majority of asthma morbidity. Understanding mechanisms that contribute to the development of severe disease is important.


OBJECTIVE
The goal of the Severe Asthma Research Program is to identify and characterize subjects with severe asthma to understand pathophysiologic mechanisms in severe asthma.


METHODS
We performed a comprehensive phenotypic characterization (questionnaires, atopy and pulmonary function testing, phlebotomy, exhaled nitric oxide) in subjects with severe and not severe asthma.


RESULTS
A total of 438 subjects with asthma were studied (204 severe, 70 moderate, 164 mild). Severe subjects with asthma were older with longer disease duration (P < .0001), more daily symptoms, intense urgent health care utilization, sinusitis, and pneumonia (P < or = .0001). Lung function was lower in severe asthma with marked bronchodilator reversibility (P < .001). The severe group had less atopy by skin tests (P = .0007), but blood eosinophils, IgE, and exhaled nitric oxide levels did not differentiate disease severity. A reduced FEV(1), history of pneumonia, and fewer positive skin tests were risk factors for severe disease. Early disease onset (age < 12 years) in severe asthma was associated with longer disease duration (P < .0001) and more urgent health care, especially intensive care (P = .002). Later disease onset (age > or = 12 years) was associated with lower lung function and sinopulmonary infections (P < or = .02).


CONCLUSIONS
Severe asthma is characterized by abnormal lung function that is responsive to bronchodilators, a history of sinopulmonary infections, persistent symptoms, and increased health care utilization.


CONCLUSIONS
Lung function abnormalities in severe asthma are reversible in most patients, and pneumonia is a risk factor for the development of severe disease.
Moore
Wendy C
WC
Center for Human Genomics, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA. wmoore@wfubmc.edu <wmoore@wfubmc.edu>
Bleecker
Eugene R
ER
Curran-Everett
Douglas
D
Erzurum
Serpil C
SC
Ameredes
Bill T
BT
Bacharier
Leonard
L
Calhoun
William J
WJ
Castro
Mario
M
Chung
Kian Fan
KF
Clark
Melissa P
MP
Dweik
Raed A
RA
Fitzpatrick
Anne M
AM
Gaston
Benjamin
B
Hew
Mark
M
Hussain
Iftikhar
I
Jarjour
Nizar N
NN
Israel
Elliot
E
Levy
Bruce D
BD
Murphy
James R
JR
Peters
Stephen P
SP
Teague
W Gerald
WG
Meyers
Deborah A
DA
Busse
William W
WW
Wenzel
Sally E
SE
D000328:Adult; D017668:Age of Onset; D001249:Asthma / Q000145:classification / Q000276:immunology / Q000503:physiopathology* / Q000628:therapy; D003695:Delivery of Health Care / Q000706:statistics & numerical data; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000378:metabolism; D010641:Phenotype; D012720:Severity of Illness Index; D012882:Skin Tests
D009569:Nitric Oxide