In-vitro-Diagnostik von Nahrungsmittel-Allergien

Summary

Measurement of allergen-specific IgE represents the most useful diagnostic in-vitro test in food allergy, usually being performed after case history and skin test. Hundreds of single allergens and combinations are offered by a number of manufacturers. Different allergens, detection and calibration methods lead to a lack of comparibility of test results, which can also differ substantially from case history, skin test and food challenge results. Cellular laboratory tests should be used for food allergy testing only in individual cases or scientific studies.

Food allergens: Food proteins of higher stability (predominantly relevant in early infancy) do rarely cause problems in terms of IgE-testing. At present, use of defined proteins for routine diagnosis of allergen-specific IgE has no advantage compared to whole food allergens. Resulting from sensitizations to pollen allergens or natural rubber latex, IgE will be found to cross reactive, mostly labile allergens from various fruit, vegetable or plant species, being clinically relevant only in case of corresponding symptoms. This supports the recommendation of selected in-vitro testing, focussing on suspected foods.

Indication for IgE-testing: Reasonable probability of food allergy, but no clear-cut evidence after case history and skin test; sensitization to foods not suitable for skin testing; severe reactions to foods; skin test or its interpretation not possible.

Interpretation of in-vitro results: False positive or negative results due to inappropriate reagents or laboratory errors; clinically irrelevant results by strongly elevated total serum IgE, low cut-off levels or cross reactive allergens.

Not suitable for diagnosis of food allergy: Allergen-specific IgG, cytotoxic food test, electro-acupuncture, bioresonance.

Unsolved problems: Optimized quality of reagents; calibration and comparability of results from different methods; serological cross reactivity. Future studies adressing clinical relevance of in-vitro results will help to improve diagnosis and interpretation of food allergy.