Identifying the components of asthma health status in children with mild to moderate asthma.
BACKGROUND
Weak and inconsistent correlations between measurements of asthma health status suggest that the disease is composed of nonoverlapping components.


OBJECTIVE
Factor analysis was used to explore the relationships between measures of asthma morbidity and to identify heterogeneous components of asthma health status in children 5 to 12 years old. Results were compared across time (baseline and 48-month visit) and treatment arms.


METHODS
Analyses were conducted in 7 different study windows in a database from a large clinical trial of children with mild to moderate asthma (n = 1041). Measurements of lung function, symptoms, and health care utilization from daily diary cards, serum IgE levels, total eosinophil count, skin test positivity, and airway hyperresponsiveness were included. Data on fractional exhaled nitric oxide and sputum eosinophil cationic protein were included in a subgroup of patients.


RESULTS
In each of the study windows, factor analysis identified 5 factors that explained between 50% and 60% of the common variance. Factors identified included (1) inflammatory markers, (2) symptoms/medication use, (3) asthma exacerbations, and measures of lung function, which subdivided into (4) FEV(1) and forced vital capacity, and (5) bronchodilator response and the FEV(1)/forced vital capacity ratio. Exploratory analyses suggest that fractional exhaled nitric oxide account for the atopy/inflammatory marker factor, and sputum measurements account for a sixth, separate factor.


CONCLUSIONS
The consistent identification of a 5-factor structure across time and treatment arms suggests that each of these factors provides independent information in the assessment of asthma.
Holt
Elizabeth W
EW
Channing Laboratory, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA. eholt@tulane.edu
Cook
Earl Francis
EF
Covar
Ronina A
RA
Spahn
Joseph
J
Fuhlbrigge
Anne L
AL
D018927:Anti-Asthmatic Agents / Q000627:therapeutic use; D001249:Asthma / Q000097:blood / Q000276:immunology / Q000503:physiopathology*; D001944:Breath Tests; D019819:Budesonide / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D047150:Eosinophil Cationic Protein / Q000032:analysis; D004804:Eosinophils; D005163:Factor Analysis, Statistical; D006304:Health Status; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood; D007223:Infant; D008297:Male; D017835:Nedocromil / Q000627:therapeutic use; D009569:Nitric Oxide / Q000378:metabolism; D016032:Randomized Controlled Trials as Topic; D012129:Respiratory Function Tests
D018927:Anti-Asthmatic Agents; D017835:Nedocromil; D009569:Nitric Oxide; D007073:Immunoglobulin E; D019819:Budesonide; D047150:Eosinophil Cationic Protein