REAST
BACKROUND
The worldwide frequency of allergies has increased significantly over the past decades. The term allergy is often used for type I hypersensitivity reactions (immediate type reactions), whose symptoms generally occur within 30-60 min after contact with the allergen. The most frequent symptoms are: hay fever (rhinitis), conjunctivitis, hives (urticaria), allergic asthma and as the most dangerous manifestation anaphylaxis (the anaphylactic shock). The allergens causing type I hypersensitivity reactions are mostly proteins derived from the natural environment e.g. plant pollen, animal hair, food, mites and insect venoms. The characteristic of type I allergies is the involvement of allergen specific immunoglobulins (antibodies) of class E (sIgE). Hence, the detection of sIgE is an important tool of modern allergy diagnostics.
The ALLERG-O-LIQ is based on the “reversed enzyme allergo sorbent test (REAST)” and represents an innovative, flexible and highly specific test system using anti-human IgE coated microtiter plates in combination with biotinylated reagents. Compared to conventional IgE detection systems all interfering serum components are removed from the system by washing. This leads to the advantage of just measuring allergen-specific IgE and finally to the high sensitivity and specificity of the test. (Download: Flyer Allerg-O-Liq)
PRINCIPLE
The Specific IgE REAST for the quantitative measurement of IgE in human serum and plasma is based on a Sandwich ELISA. During the first incubation step total IgE from the patient sample is captured by anti-human IgE coated to the microwells. By a washing procedure surplus serum components are removed from the well whereas IgE remains bound to the solid phase surface. During the next incubation step biotinylated allergen is added and incubated in the microwells. After a further washing step detection of bound allergen is carried out with a streptavidin/peroxidase (HRP)-conjugate forming complexes consisting of specific IgE/biotinylated allergen/HRP-conjugate. The wells are washed again, and the substrate solution 3,3′,5,5′-Tetra-Methyl-Ben¬zidine (TMB) is added and incubated, resulting in the development of a blue color. After stopping the enzymatic reaction with acid the color changes into yellow. The optical density (OD) of the colored product is measured spectrophotometrically at 450 nm (reference wave length 620 nm). The sIgE concentration of the patient sample is proportional to the optical density. Calibrators with defined concentrations of IgE (calibrated against WHO standards) are assayed simultaneously with the patient samples to generate a calibration curve. Unknown IgE concentrations of the test samples are calculated from this curve. (Download IFU: 0520960FL / 0524800FL)
AVAILABLE ALLERGENS
For the performance of specific IgE are beside 500 complete allergen extracts and allergen mixtures (see current allergen list) also recombinant and native, highly purified allergens available. (Download: List of recombinant allergens). So a complete screening of the patients is possible.
Here you can find the current list of allergens:
TOTAL IgE
Allergic reactions of the immediate type (Type I allergies) are mediated by allergen specific Immunoglobulin of class E (IgE). Mostly, the occurrence of allergen specific IgE is accompanied by increased titers of total IgE in the blood of the patients. In these cases the titer can increase up to 1000fold. Therefore the serological determination of total IgE (Download: 08102CP/08101FL) beside the determination of specific IgE is an important diagnostic tool for patients with suspected type I allergies
SYSTEMS
There are three different system available for the determination of specific IgE and total IgE as well as ECP. Essential are the requirements, demands and perceptions of the operator. Basically we distinguish between the following possibilities of performing the test:
