[CROATIAN GUIDELINES FOR IN VITRO DIAGNOSIS OF IgE MEDIATED HYPERSENSITIVITY].

In vitro diagnostic procedure in allergology includes determination of serum levels of total and allergen specific IgE antibodies, allergen specific IgG antibodies, plasma tryptase, eosinophil cationic protein (ECP) and basophil activation test (BAT). In vitro tests should be used according to clinical history, physical examination, and in vivo methods for allergy testing. Clinical relevance of elevated total IgE in allergy diagnosis is modest, since it can be caused by other conditions. Elevated serum levels of allergen specific IgE antibodies, together with positive medical history, are indicative of clinically relevant allergy. A recommended laboratory method for total and specific IgE concentration measurement is the sandwich-type fluoroimmunoassay ImmunoCAP, considered as an ideal immunoassay. Serum levels of allergen specific IgG antibodies have no proved clinical relevance in food allergy diagnosis. They can be useful to monitor venom immunotherapy success, as well as to estimate the risk of venom induced anaphylaxis. Elevated plasma tryptase (subtype ß) level is an indication of mast cell activation caused by specific allergen. It should be obtained within 4 hours after an anaphylactic episode. Elevated level of ECP can be detected in patient blood during late phase of allergic reaction. It can be used to monitor patients with chronic allergenic and inflammatory conditions in which eosinophils play a central role. BAT includes measurement of CD 63 (cluster of differentiation) and CD 203 antigens of the molecular surface by flow cytometry. It is useful in the diagnosis of venom, food and drug allergy, estimation of severity of allergic disease and natural tolerance to allergens. In vitro tests based on allergen extracts can be used for in vitro diagnosis in monosensitized patients with clear medical history and symptomatic treatment. Molecular allergy diagnosis should be performed in special clinical indications such as diagnosis of cross reactivity, prescription of specific immunotherapy (especially in polysensitized patients with complex symptoms), diagnosis of idiopathic or cofactor induced anaphylaxis, latex allergy, and assessment of the risk of allergic reaction to specific allergen.

House dust mite subcutaneous immunotherapy does not induce new sensitization to tropomyosin: does it do the opposite?

BACKGROUND: It is still uncertain whether house dust mite (HDM) tropomyosin present in allergen extracts can cross-sensitize patients receiving subcutaneous immunotherapy (SCIT) and thus induce food allergy. OBJECTIVES: Our aim was to assess whether new sensitization to tropomyosin occurred during HDM-SCIT, and, if so, whether it was clinically relevant. PATIENTS AND METHODS: The study sample comprised 56 HDM-allergic patients treated with SCIT using HDM extract. All patients were screened for specific IgE (sIgE) to mite tropomyosin (rDer p 10) before and after SCIT. In patients with a positive result, we also monitored the dynamics of sIgE to rDer p 10 and shrimp tropomyosin (rPen a 1) at several time points. The levels of sIgE were measured using the CAP System fluorescent-enzyme immunoassay. RESULTS: sIgE to tropomyosin was found in only 5 patients, 3 of whom expressed low and clinically irrelevant levels of sIgE to Der p 10, while sIgE to Pen a 1 was not found. The remaining 2 patients expressed sIgE to both tropomyosins. In the first, the initial increase and subsequent decrease resembled the dynamics of the IgE antibodies usually seen in SCIT patients and were never accompanied by seafood-induced symptoms. In the other, a decrease in levels of sIgE to both tropomyosins resulted in the complete loss of his reactivity toward seafood. CONCLUSIONS: Immunotherapy using HDM extracts does not induce clinically relevant sensitization to tropomyosin. In certain cases of combined mite and seafood allergy, treatment may even lead to the improvement of food allergy symptoms. The levels of sIgE to Der p 10 and Pen a 1 may be useful monitoring markers.