MedWire News: Total immunoglobulin (Ig)E levels are associated with asthma in atopic but not nonatopic individuals, study results show.
Furthermore, asthma independent of the presence of IgE is not uncommon, say Peter Gergen (National Institute of Allergy and Infectious Diseases, Bethesda, Maryland, USA) and team.
Writing in the Journal of Allergy and Clinical Immunology, the researchers explain: “Allergy has long been known to play an important role in asthma [and] sensitization to specific allergens can make asthma more difficult to control.”
But they add: “The extent of asthma related to IgE-mediated sensitization is controversial.”
To determine the association between total IgE levels and asthma, the team studied data on a nationally representative sample of 7398 people, aged 6 years and older, who participated in the National Health and Nutrition Examination Survey (NHANES) 2005-2006. The NHANES 2005-2006 was the first such nationwide survey to include assessment of total and allergen-specific IgE antibodies in the US population.
Overall, the prevalence of current asthma was 8.8%, the prevalence of atopy was 42.5%, and the median total IgE level was 40.8 kU/l.
The researchers found that the adjusted odds ratio (OR) for asthma in patients with a 10-fold increase in total IgE level was 2.18.
However, total IgE levels predicted asthma prevalence only among people who were atopic. Indeed, the adjusted odds ratio (OR) for the association between total IgE levels and asthma was 2.41 among atopic participants compared with 1.11 among nonatopic individuals.
Among atopic participants, the association between total IgE level and asthma became stronger as the number of positive specific IgE test results increased.
Nevertheless, asthma was also present at even the lowest levels of total IgE, regardless of atopic status.
The researchers also note that 92% of atopic participants were identified by six specific IgEs, but 11 specific IgEs were required to increase the identification rate to 99%.
Gergen and team conclude: “Among the US population 6 years and older, total serum IgE levels were associated with doctor-diagnosed current asthma but only among persons who were atopic, as defined by a panel of allergen-specific IgE tests. Total IgE levels, in the absence of specific IgE, are not associated with asthma.”
They add: “In the US population asthma independent of the presence of IgE is not uncommon,” and advise that “total IgE measurement should not be routine in the evaluation of subjects with asthma.”
MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a part of Springer Science+Business Media. © Current Medicine Group Ltd; 2009
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