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Keywords:

  • Asthma;
  • Paediatrics;
  • Reference values;
  • Respiratory function test;
  • Severity of Illness index

Abstract

Aim:  Measures of lung function (usually FEV1 <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 FEV1 values were significantly reduced in children with problematic severe asthma, yet FEV1 <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 FEV1 to be 90% predicted in this population (sensitivity 61%, specificity 83%). Baseline FEV1/FVC and FEF25–75 values were not superior to FEV1 in discriminating problematic severe asthma, and neither exhaled nitric oxide levels nor bronchial hyperresponsiveness differentiated between the two asthmatic study populations.

Conclusion:  Spirometric measurements are insensitive discriminators of problematic severe asthma in childhood.