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We wish to reply to Drs Raza, Kurukulaaratchy and Arshad who commented on our recent article.1 Our primary aim for making a severity score was to try to predict the prognosis of early life obstructive airways disease, independent of invasive examinations or measurements, and easily applicable for use in other studies and in primary care. Thus it is not clear to us why Raza et al find the factors used in our severity score difficult to define, including our use of hospitalisations for obstructive airways disease. In our view, hospital admission because of bronchial obstruction is an objective measure of severity, which is easily verified and recorded.
They question the use of diagnosed current asthma as the outcome, suggesting that this may reduce the validity of the tool and criticise that bronchial hyperresponsiveness (BHR) was not used to consolidate the diagnosis of asthma. We disagree with both of these comments. In fact, as was clearly stated, exercise induced bronchoconstriction (EIB; a measure of BHR) is part of our well defined term “current asthma” used for the 10 year follow-up study of our birth cohort, including studies on asthma prevalence,2 lung function at birth versus asthma at 10 years of age3 and asthma genetics.4 Our definitions of asthma and current asthma are stricter than in many other studies including, but not limited to, “wheeze” alone, requiring at least two out of three criteria (symptoms/medication or the presence of EIB in the last year or during the investigation) to acquire a definition of asthma.2 While “wheeze” as the outcome may be appropriate in English speaking countries, it is not a term used in most other languages. Consequently, it appears less stringent, more prone to subjective reporting but nonetheless seems to be more frequent in our2 and other studies than a history of asthma and current asthma. Furthermore, the authors themselves have also used the term “asthma” when reporting from their own birth cohort study.5
Raza et al further criticise the fact that we did not cite their paper,6 describing their risk score for persistent wheeze at the age of 10 years. Although this may be an omission, our aim was not a retrospective risk assessment of persistent wheeze but prospectively to assess the risk for current asthma at 10 years in children with recurrent bronchial obstruction at 2 years. Furthermore, as the authors themselves demonstrated in their cohort, the positive predictive value (PPV) for wheeze at 10 years from the score applied at 4 years was much higher than when applied at 2 years (PPV = 0.475),6 which is considerably less than our 2 year score. The severity score applied is probably age specific, highlighted by our own score which was not found to be useful at 1 year of age.1
In our view, the comments of Raza et al do not diminish the validity of our severity score, but we stress that the present as well as any other scores must be confirmed in other studies in different populations before any general acceptance can be reached.
Competing interests: None.
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