Both SPT and sIgE needed to confirm atopy in severe childhood asthma
MedWire News: While the skin prick test (SPT) and allergen-specific immunoglobulin E (sIgE) tests are equally able to identify atopy in children with severe asthma, both tests should be performed due to poor concordance on individual allergens, say UK scientists.
Severe, therapy-resistant asthma is defined as asthma with chronic symptoms, acute severe exacerbations, and fixed airflow obstruction apparently unresponsive to high-dose medications. Reduction of allergen burden is a logical strategy, but there is no gold standard test for defining atopy in children, explain Andrew Bush and colleagues, from the Royal Brompton Hospital in London.
The team examined the utility of SPT and sIgE atopy tests in 47 children, aged an average of 11.8 years, with severe, therapy-resistant asthma.
Overall, 89% of the patients were classified as atopic (defined as a positive result on either test); with 87% identified on the SPT and 89% on the sIgE test. There was 98% concordance between the two tests in identifying children as atopic or non-atopic.
However, when each allergen of the panel was considered individually, there was 20% discordance between the SPT and sIgE, with the SPT negative and sIgE positive in 12.5% of cases, and the SPT positive and sIgE negative in 7.5% of cases.
The team notes that the sIgE test was more likely to detect sensitization to house dust mites, cats, trees, and grasses than the SPT, while the SPT was more likely to identify dog sensitization.
Interestingly, there was moderate correlation between the sum of sIgE and the sum of SPT weal diameter from the standard panel. However, the correlation between total IgE and sum of SPT weal diameter was poor, even though there was very good correlation between total IgE and the sum of sIgEs.
The researchers conclude in the journal Clinical and Experimental Allergy: "Rather than performing SPT in the first instance in the management of children with severe therapy-resistant asthma, followed by further testing including sIgE at a later stage, both tests should be performed at the outset in order to more accurately identify sensitization to individual allergens."
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By Liam Davenport