Series on clinical testing. 1. The diagnostic usefulness of specific IgE antibody measurements

In vitro measurements of specific IgE antibodies are useful in the evaluation of patients with diseases characterized by clinical signs of immediate hypersensitivity. In general, measurable levels of specific IgE antibodies indicate immediate hypersensitivity to the allergen tested regardless of the clinical expression of allergy. With the exception of low-level specific IgE antibodies to milk and egg antigens in children and to other foods in unselected adults, false-positive results are rare. However, despite the high probability that positive test results represent allergic disease, some patients with clinically apparent respiratory allergy have borderline or negative test results to certain allergens, and uncommon hypersensitivities such as those elicited by drug and insect-venom allergens may be missed if antibody testing is not performed at the appropriate time following antigen exposure. For these reasons, in vitro IgE antibody measurements are not recommended as screening tests for respiratory allergic diseases or drug or insect-venom hypersensitivities. Useful information is obtained by in vitro testing in these diagnostic situations only when tests are performed on carefully chosen patients.