Introduction Skin prick tests (SPTs) and measurement of allergen-specific serum (s)IgE are the main diagnostic tools for confirming atopy. Results of both tests are usually reported as dichotomous (sensitised/not sensitised), using arbitrary cut-offs which are the same across different ages and genders (SPT >3 mm, sIgE >0.35 kU/L). We investigated the influence of age and gender on allergy test results as biomarkers of asthma during childhood.
Methods Children in a population-based birth cohort (n = 1051) were followed from birth to age 11 years. Information on asthma/wheeze (questionnaires), SPTs and sIgE to inhalant allergens (mite, cat, dog) were collected at ages 3, 5, 8 and 11 years. We investigated the association between quantitative atopy (sum of SPT mean wheal diameters [MWD]/titres of sIgE) and wheeze/asthma across ages and genders.
Results There was a significant association between the SPT MWD/sIgE titre and wheeze/asthma at all ages and for both genders. However, the strength of this association was age and gender-dependent. For SPTs, the strength of the association between MWD and asthma increased with increasing age (OR 1.14–1.20, p = 0.002); we observed the opposite pattern for sIgE titre (OR 0.97–0.99, p = 0.04). For any given SPT/sIgE level, boys were significantly more likely to express clinical symptoms, particularly in early life; this difference between males and females appeared to diminish with age, and was no longer significant by age 11 years.
Conclusions Age and gender have to be taken into account when interpreting the results of allergy tests (skin tests and IgE measurement) in the context of asthma during childhood.