Food allergy blood tests unreliable

A study at Johns Hopkins Children's Center last July suggests that too-heavy reliance on blood tests alone to predict IgE-mediated allergic reactions may not be a good idea.

Researchers compared the three most widely used commercial IgE blood tests, ImmunoCap, Turbo RAST and Immulite. Using ImmunoCap as a reference because of its well documented past performance, Immulite failed to pick up peanut antibodies in three out of 50 positive samples, while Turbo RAST failed to detect peanut antibodies in 11 out of 50 positive samples. Immulite failed to detect soy antibodies in one out of 17 positive samples, while Turbo RAST failed to detect soy antibodies in five out of 17 positive samples.

Moreover, ImmuLite tended to overestimate the amount of antibodies, while Turbo RAST found fewer antibodies than were actually present.

Overestimating the number of antibodies could lead a physician to believe that a person is allergic when he or she is not, while underestimating the antibodies could mean that no allergy would be diagnosed where there is one.

First published in January 2008

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