Background: Dosages of anti-immunoglobulin (Ig)E in treatment of allergic asthma is based on total IgE body pool assuming that IgE antibodies responsible for the disease are evenly distributed among patients. This assumption was evaluated.
Methods: Median and quartile concentrations of IgE and IgE antibodies to cat and mite in 6461 sera submitted to an allergy laboratory during 2003–2005 were calculated and expressed in groups of different IgE levels.
Results: Of 3872 (60%) samples from adults with a serum IgE level of 30–700 kU/l, 22.2% had IgE antibodies (≥0.35 kUA/l) to mite, 36.0% to cat and 8.1% to both. The relative concentration of IgE antibody of IgE decreased with increasing IgE, indicating a more specific response in patients with slightly elevated serum IgE. At a hypothetical serum IgE level of 10 kU/l, the threshold recommended for anti-IgE treatment, 25% of the originally mite- and/or cat-positive population in the <75 kU/l IgE group still would have detectable IgE antibodies.
Conclusions: Sera from patients sensitized to mite and cat with moderate serum IgE levels have a high proportion of IgE antibodies; in the 30–74 kU/l group, as much as 10% of the IgE could be specific to one allergen. An increase of the anti-IgE dosage given to such patients should be considered, especially because IgE antibodies with different, relevant specificities have an additive effect in triggering inflammatory cells.