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Comparison of the AllergyScreen (MEDIWISS Analytic, Moers) with the Skin Test (HAL, Düsseldorf -in-vivo) and the CAP-System (Pharmacia, Freiburg -in-vitro ).
Release time：2020/11/18
Author：W. Kersten
Keywords: AllergyScreen, CAP-systeme, skin test, in-vitro diagnostic methods, specific IgE
Summary:
Screening tests with the aid of multiallergen combinations facilitate the clarification of a wide range of allergens in the serum. Depending on the test mixture, with this method proof of sensitisation is possible not only for a single allergen, but also for a complete allergen group. These tests are also helpful in doubtful anamnestic situations, and where it is necessary to ascertain results with comparitively small quantities of serum.
Comparison of the AllergyScreen concept with the established single system of Pharmacia and the Skin Test has shown that this is a convincing method for determining a comprehensive specific sensitisation pattern in the patient. This can be achieved quickly at low cost, and with minimum material expenditure, which is not possible with single allergen determinations. The sensitivity and specificity of the system is very closely approximate to skin testing, and corresponds to a conventional single allergen system.
Data of the mean sensitivity: AllergyScreen/Skin prick test: 95.1%; AllergyScreen/CAP: 84.3%, CAP/Skin prick test: 95.8%; data of the mean specificity: AllergyScreen/Skin prick test: 80.2%, AllergyScreen/CAP: 95%; CAP/Skin prick test: 76.1%; data of the mean agreement: AllergyScreen/Skin-Prick test: 88.3%, AllergyScreen/CAP: 90.6%; CAP/Skin prick test: 87.5% The nitrocellulose membranes are situated in a plastic reaction trough, in which all working operations are carried out one after the other. A horizontal or tilting shaker is also necessary for the operation. The patient’s serum is pipetted into the reaction trough, and this is incubated at room temperature. Here the allergen-specific IgE antibodies react with the allergen, and are thus bound to the nitrocellulose membranes through the allergens. Non-bound substrate is removed by washing. This is followed by the addition of an anti-human IgE antibody coupled with biotin. This binds onto the respective specific IgE from the first incubation in the test fields. Non-bound detector antibodies are removed by washing. A streptavidin conjugated with alkaline phosphatase is then added. This binds onto the biotin from the second incubation in the test fields and onto the positive control. Non-bound streptavidin conjugate is removed by washing. After the addition of BCIP dye, an enzymatic colour reaction of the alkaline phosphatase takes place, with the formation of precipitates on the test strips in accordance with a specific reaction. The colouration is directly proportional to the content of specific antibody in the serum sample (fig. 1).
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