A sample of blood serum is applied to a plastic disk to which the test antigen or allergen is attached. An enzyme-linked marker is added, which causes a color change if your serum contains antibodies to the antigen tested. Test procedure Blood is drawn from your vein and sent to a laboratory for analysis. Factors affecting results High levels of one type of antibody may prevent low levels of another antibody against the same substance from being detected. The test demonstrates the amount of IgA, IgG, and IgM antibodies in a milliliter of serum.
Interpretation varies with the reason for the test.
Since treatment of insect allergies leads to production of IgG, a high level can mean that the treatment is successful. Similarly, since IgG is produced in response to an aspergillosis infection, a high level indicates a recent infection. Advantages It's relatively inexpensive. No radioactive materials are involved. It does not detect IgE, the antibody most commonly involved in allergic reactions.