Severity of obstructive airways disease by two years predicts asthma at 10 years of age

¹ Department of Paediatrics, Division of Woman and Child, Ullevål University Hospital, Norway
² Division of Woman and Child, Ullevål University Hospital, University of Oslo, Norway
³ Division of Woman and Child, Ullevål University Hospital, Norway
⁴ Voksentoppen, Dept. of Paediatrics,Rikshospitalet- Radiumhospitalet Medical Center, Oslo, Norway
⁵ Voksentoppen, Dept. of Paediatrics,Rikshospitalet- Radiumho, Faculty of Medicine, University of Oslo, Norway

^* To whom correspondence should be addressed. E-mail: k.h.carlsen{at}medisin.uio.no.

Accepted 12 June 2007

	Abstract

Background: Predicting school-age asthma from obstructive airways disease (OAD) in early life is difficult, even considering parental and children's atopic manifestations.

Study objective: To assess if severity of OAD in the first two years of life predicts asthma at 10 years of age.

Methods: From a nested case control study within the Environment and Childhood Asthma study, 233 two year old subjects with recurrent (two episodes) of bronchial obstruction (BO)(rBO+) and 216 subjects without BO (rBO-) underwent clinical examination, parental interview, treadmill test and metacholine bronchial hyperresponsiveness (BHR) measurement at 10 years. A severity score at two years was calculated by frequency, persistence of bronchial obstruction and hospital admissions due to OAD.

Main outcomes: Current asthma at 10 years (asthma with symptoms and/or asthma medication during the last year and/or positive treadmill test). Secondary outcome; metacholine BHR at 10 years.

Results: Compared to rBO- subjects; adjusted odds ratio (95 % confidence intervals) of current asthma among rBO+ was 7.9 (4.1, 15.3), among rBO+ with severity score >5: 20.2 (9.9, 41.3). In ROC analysis, positive and negative predictive values demonstrated the applicability and value of the score with optimal cut off at severity score 5. Children with severity score >5 had more often severe BHR (PD20-metacholine < 1 µmol) than children with a lower or 0 score (p=0.0041).

Conclusion: Using a simple scoring system, a high severity score of OAD by two years of age is a strong risk factor for, and may predict current asthma at ten years of age.

Keywords: Birth cohort, Childhood asthma, Prediction, Risk, Severity score