Inappropriately applied laboratorybased tests

There are laboratory-based tests, some in common usage, which have not been shown to identify food allergies or intolerances with any accuracy. Lymphocyte subset counts and lymphocyte function assays are useful for diagnosing congenital or acquired lymphocyte cellular immunodeficiency states, but not allergic disease. Cytokines and their receptors are involved at many levels of the immune response. The correlation of assays with disease, and in particular their diagnostic value, is yet to be established.

It has been suggested that food immune complexes may play a role in those who claim a delayed (>2 hours) adverse response to foods. These are able to be detected using solid phase radioimmunoassay. Even within autoimmune diseases that rely on their presence as diagnostic, their role is unclear. Their clinical relevance is doubtful for two further reasons. They have not been subjected to comparison with DBPCFC, enabling the calculation of sensitivities and specificities. It is also thought that they are probably a normal phenomenon.

Laboratories are able to measure very small amounts of chemicals present in samples of biological material. These are certainly very important to measure where there is clinical concern over toxicity, as with serum levels of lead in cases of concern over lead poisoning, for example. There is no evidence that the chemicals implicated have any part to play in allergic disease. There is also no evidence that deficiencies in vitamins, minerals and amino acids play any part in the allergic response, and thus measuring them is unlikely to be of diagnostic help.

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