Unreliability of IgE/IgG4 antibody testing as a diagnostic tool in food intolerance

Background Some clinicians link chronic disease in certain patients to 'foo d intolerance'. This is currently diagnosed by exclusion dieting, a time-co nsuming and tedious technique. It has been claimed that IgE/IgG4 antibody t esting is a rapid and valid method of determining food intolerance. Objective To determine the test/retest reliability of IgE/IgG4 antibody tes ting as a diagnostic tool. Methods Blinded testing of duplicate blood samples from nine patients with suspected food intolerance was undertaken by tertiary referral centre using the services of a commercial laboratory. The proportions of consistent and inconsistent results for tests of 95 different foods were analysed. Results Test/retest reliability was low. Even though the study method syste matically overestimated kappa, this value never exceeded 0.51, regardless o f the statistical model used. All but one patient had a greater number of i nconsistent results than had been prespecified as an unacceptable level of disagreement. In one case, 50 out of 95 test results were inconsistent on r etest. Conclusions We found no evidence that IgE/IgG4 antibody testing as performe d by this laboratory is a reliable diagnostic tool.