Identifying problematic severe asthma in the individual child--does lung function matter?
OBJECTIVE
Measures of lung function (usually FEV(1) <80% predicted) are used to classify asthma severity in both adults and children, despite evidence that lung function impairment is less pronounced in the paediatric asthma population. The present study assesses the relevance of lung function measurements as discriminators of severe childhood asthma.


METHODS
Fifty-one school-aged children with problematic severe asthma, 37 mild-to-moderate asthmatics and 29 healthy controls underwent a comprehensive clinical work-up. Problematic severe asthma was defined in patients exhibiting poor asthma control despite high-dose inhaled corticosteroid treatment and at least one other asthma controller drug. Mild-to-moderate asthmatic children used low-dose inhaled steroids and reported minimal asthma symptoms.


RESULTS
Baseline FEV(1) values were significantly reduced in children with problematic severe asthma, yet FEV(1) <80% predicted showed a low sensitivity (41%) for discriminating severe vs. mild-to-moderate asthma. Receiver-operated characteristic analysis estimated the optimal cut-off of FEV(1) to be 90% predicted in this population (sensitivity 61%, specificity 83%). Baseline FEV(1)/FVC and FEF(25-75) values were not superior to FEV(1) in discriminating problematic severe asthma, and neither exhaled nitric oxide levels nor bronchial hyperresponsiveness differentiated between the two asthmatic study populations.


CONCLUSIONS
Spirometric measurements are insensitive discriminators of problematic severe asthma in childhood.
Lang
A M
AM
Department of Paediatrics, Oslo University Hospital, Oslo, Norway. astrima@online.no
Konradsen
J
J
Carlsen
K-H
KH
Sachs-Olsen
C
C
Mowinckel
P
P
Hedlin
G
G
Lødrup Carlsen
K C
KC
D000293:Adolescent; D001249:Asthma / Q000175:diagnosis* / Q000503:physiopathology; D016022:Case-Control Studies; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008450:Maximal Midexpiratory Flow Rate; D011237:Predictive Value of Tests; D012372:ROC Curve; D012129:Respiratory Function Tests / Q000379:methods; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D014797:Vital Capacity