[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 β) 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.