The RAST (radioallergy separation) test is one of the most important methods used in the diagnosis of allergies. It requires a serum sample from the patient. The entire procedure for assessing an allergic response takes place in a laboratory. The diagnosed person has no direct contact with the sensitizing substance. The RAST test does not require the discontinuation of antiallergic drugs, which is its great advantage. What is this diagnostic method? What should you know about the RAST test?
Contents:
- RAST test and the mechanism of allergic reactions
- RAST test and cutaneous allergy diagnosis methods: comparison
- RAST test as an in vitro diagnostic method
- RAST test: pros and cons
- RAST test: when is it done?
Radioallergy separation test( RAST ) is used in allergy diagnosis. In this method, a blood serum sample is tested. It is assessed in a laboratory to identify any patient sensitizing substances. This procedure uses a radioimmunoassay to detect specific IgE antibodies.
RAST differs from popular skin allergy tests in that the test is performed in vitro. This means that all tests are performed on laboratory glass, after the patient has been sampled. Skin tests are still the most popular in the diagnosis of allergies. They assess the presence of allergies based on skin reactions in response to contact with various substances.
RAST test and the mechanism of allergic reactions
Allergy results from abnormal body reactions when in contact with certain substances. In her case, the immune mechanisms are over-activated. It is about the body's defensive reactions that are inadequate to the stimulus. For example, grass pollen is relatively neutral to the human body. However, the immune system of the allergy sufferer will "fight" against them. Such an irrational battle has negative consequences for our he alth and well-being.
The diagnosis of allergies is not easy. It requires a lot of complex tests. However, the most important thing in the whole process is the medical history. In order to confirm the specialist's assumptions, it is performedappropriate research. The most popular of them are skin tests and methods involving the determination of IgE antibodies in a blood sample. The RAST procedure belongs to this second type of research.
RAST test and cutaneous allergy diagnosis methods: comparison
Skin tests are performed for virtually all types of allergies. The most important application is for the contact and inhalation type of this disease. However, there are medical situations in which this method is not effective.
An example of one of them is atopic dermatitis. Skin test results will not be measurable with this disorder.
The RAST test is also used in situations where skin methods give results inconsistent with the medical history.
This method is used as:
- supplement to the diagnosis of food allergy
- insect venom allergy test
- latex allergy diagnosis
Choosing the right method of allergy diagnosis is not easy. The decision to choose it depends on:
- current knowledge about the sensitivity of the test
- specificity of the method
- predictive value of the test for information from the medical history
RAST as an in vitro diagnostic method
The fact that the RAST test is an in vitro allergy diagnosis method means that the test is performed after taking a sample from the patient in a laboratory. In this case, only the serum IgE pool is assessed.
There are many different methods of this type in laboratory use. They differ in the type of carrier used and the method of detecting the antibodies. The RAST test is distinguished by the fact that radioisotopes are used in this procedure to detect specific IgE.
IgE are antibodies that play an important role in he althy immune responses. They are an important element in the body's fight against parasites. They induce the secretion of histamine by eosinophils and basophils in response to danger. However, the same mechanisms can lead to pathological reactions leading to the development of allergies.
IgE is strongly associated with an allergic response to specific substances. For this reason, their specificity is used in medical research. For example, if a person shows high levels of IgE against pollen in a laboratory test, they are likely allergic to pollen.
RAST test: mileage
A serum sample is taken from the patient to perform the test. Then it is tested on a glass plate on which it is embeddedare standardized antigens. If the serum contains antibodies to the allergen, they bind to the allergen. The course of the reaction is detected by labeling with radioactive isotopes.
RAST test: advantages and disadvantages
As the patient does not come into direct contact with the allergen in this method, there is no risk of a violent allergic reaction in the body. Such a risk exists in the case of skin testing.
The test can be performed while taking antihistamines. Thanks to this, the patients do not have to give up pharmacological therapy before the test is performed.
The RAST test can be performed on children of all ages. Skin tests give diagnostic results only in patients after the age of three.
The RAST test is definitely more expensive than other diagnostic methods. The results of the study are not unequivocal. They require an accurate assessment by a specialist doctor.
RAST test: when is it done?
- When your doctor advises you not to stop taking antihistamines that interfere with skin test results.
- In the event of serious skin lesions in a patient.
- If a high allergen sensitivity is suspected and direct contact with the substance in the course of skin testing could have serious side effects.
Allergens: types. List of allergens
Inhaled allergy: causes, symptoms and treatment
Food allergy: causes. Which foods cause a food allergy?
About the author
Sara Janowska, MA in pharmacyPhD student of interdisciplinary doctoral studies in the field of pharmaceutical and biomedical sciences at the Medical University of Lublin and the Institute of Biotechnology in Białystok. A graduate of pharmaceutical studies at the Medical University of Lublin with a specialization in Plant Medicine. She obtained a master's degree defending a thesis in the field of pharmaceutical botany on the antioxidant properties of extracts obtained from twenty species of mosses. Currently, in his research work, he deals with the synthesis of new anti-cancer substances and the study of their properties on cancer cell lines. For two years she worked as a master of pharmacy in an open pharmacy.
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