Radioallergosorbent test

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radioallergosorbent test
MeSH D011852
LOINC 13834-7

A radioallergosorbent test (RAST) is a blood test using radioimmunoassay test to detect specific IgE antibodies in order to determine the substances a subject is allergic to. This is different from a skin allergy test, which determines allergy by the reaction of a person's skin to different substances.[ citation needed ]

Contents

Medical uses

The two most commonly used methods of confirming allergen sensitization are skin testing and allergy blood testing. Both methods are recommended by the NIH guidelines and have similar diagnostic value in terms of sensitivity and specificity. [1] [2]

Advantages of the allergy blood test range from: excellent reproducibility across the full measuring range of the calibration curve, it has very high specificity as it binds to allergen specific IgE, and extremely sensitive too, when compared with skin prick testing. In general, this method of blood testing (in-vitro, out of body) vs skin-prick testing (in-vivo, in body) has a major advantage: it is not always necessary to remove the patient from an antihistamine medication regimen, and if the skin conditions (such as eczema) are so widespread that allergy skin testing cannot be done. Allergy blood tests, such as ImmunoCAP, are performed without procedure variations, and the results are of excellent standardization. [3]

Adults and children of any age can take an allergy blood test. For babies and very young children, a single needle stick for allergy blood testing is often more gentle than several skin tests. However, skin testing techniques have improved. Most skin testing does not involve needles and typically skin testing results in minimal patient discomfort.[ citation needed ]

Drawbacks to RAST and ImmunoCAP techniques do exist. Compared to skin testing, ImmunoCAP and other RAST techniques take longer to perform and are less cost effective. [4] Several studies have also found these tests to be less sensitive than skin testing for the detection of clinically relevant allergies. [5] False positive results may be obtained due to cross-reactivity of homologous proteins or by cross-reactive carbohydrate determinants (CCDs). [6]

In the NIH food guidelines issued in December 2010 it was stated that “The predictive values associated with clinical evidence of allergy for ImmunoCAP cannot be applied to other test methods.” [7] With over 4000 scientific articles using ImmunoCAP and showing its clinical value, ImmunoCAP is perceived as “Gold standard” for in vitro IgE testing [8] [9]

Method

The RAST is a radioimmunoassay test to detect specific IgE antibodies to suspected or known allergens for the purpose of guiding a diagnosis about allergy. [10] [11] IgE is the antibody associated with Type I allergic response: for example, if a person exhibits a high level of IgE directed against pollen, the test may indicate the person is allergic to pollen (or pollen-like) proteins. A person who has outgrown an allergy may still have a positive IgE years after exposure.[ citation needed ]

The suspected allergen is bound to an insoluble material and the patient's serum is added. If the serum contains antibodies to the allergen, those antibodies will bind to the allergen. Radiolabeled anti-human IgE antibody is added where it binds to those IgE antibodies already bound to the insoluble material. The unbound anti-human IgE antibodies are washed away. The amount of radioactivity is proportional to the serum IgE for the allergen. [12]

RASTs are often used to test for allergies when:

Scale

The RAST is scored on a scale from 0 to 6:

RAST RatingIgE Level (kU/L)Comment
0level < 0.35Absent or undetectable allergen specific IgE
10.35 ≤ level < 0.70Low level of allergen specific IgE
20.70 ≤ level < 3.50Moderate level of allergen specific IgE
33.50 ≤ level < 17.50High level of allergen specific IgE
417.50 ≤ level < 50.00Very high level of allergen specific IgE
550.00 ≤ level < 100.00Ultra high level of allergen specific IgE
6level ≥ 100.00Extremely high level of allergen specific IgE

History

The market-leading RAST methodology was invented and marketed in 1974 by Pharmacia Diagnostics AB, Uppsala, Sweden, and the acronym RAST is actually a brand name. In 1989, Pharmacia Diagnostics AB replaced it with a superior test named the ImmunoCAP Specific IgE blood test, which literature may also describe as: CAP RAST, CAP FEIA (fluorenzymeimmunoassay), and Pharmacia CAP. A review of applicable quality assessment programs shows that this new test has replaced the original RAST in approximately 80% of the world's commercial clinical laboratories, where specific IgE testing is performed. The newest version, the ImmunoCAP Specific IgE 0-100, is the only specific IgE assay to receive FDA approval to quantitatively report to its detection limit of 0.1kU/L. This clearance is based on the CLSI/NCCLS-17A Limits of Detection and Limits of Quantitation, October 2004 guideline.[ citation needed ]The guidelines for diagnosis and management of food allergy issues by the National Institute of Health state that:

In 2010 the United States National Institute of Allergy and Infectious Diseases recommended that the RAST measurements of specific immunoglobulin E for the diagnosis of allergy be abandoned in favor of testing with more sensitive fluorescence enzyme-labeled assays. [13]

See also

Related Research Articles

Allergy Immune system response to a substance that most people tolerate well

Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic dermatitis, allergic asthma, and anaphylaxis. Symptoms may include red eyes, an itchy rash, sneezing, a runny nose, shortness of breath, or swelling. Food intolerances and food poisoning are separate conditions.

An allergen is a type of antigen that produces an abnormally vigorous immune response in which the immune system fights off a perceived threat that would otherwise be harmless to the body. Such reactions are called allergies.

Allergic rhinitis Human disease

Allergic rhinitis, of which the seasonal type is called hay fever, is a type of inflammation in the nose that occurs when the immune system overreacts to allergens in the air. Signs and symptoms include a runny or stuffy nose, sneezing, red, itchy, and watery eyes, and swelling around the eyes. The fluid from the nose is usually clear. Symptom onset is often within minutes following allergen exposure, and can affect sleep and the ability to work or study. Some people may develop symptoms only during specific times of the year, often as a result of pollen exposure. Many people with allergic rhinitis also have asthma, allergic conjunctivitis, or atopic dermatitis.

Immunoglobulin E Immunoglobulin E (IgE) Antibody

Immunoglobulin E (IgE) is a type of antibody that has been found only in mammals. IgE is synthesised by plasma cells. Monomers of IgE consist of two heavy chains and two light chains, with the ε chain containing four Ig-like constant domains (Cε1–Cε4). IgE is thought to be an important part of the immune response against infection by certain parasitic worms, including Schistosoma mansoni, Trichinella spiralis, and Fasciola hepatica. IgE is also utilized during immune defense against certain protozoan parasites such as Plasmodium falciparum. IgE may have evolved as a defense to protect against venoms.

Food allergy Hypersensitivity reaction to a food

A food allergy is an abnormal immune response to food. The symptoms of the allergic reaction may range from mild to severe. They may include itchiness, swelling of the tongue, vomiting, diarrhea, hives, trouble breathing, or low blood pressure. This typically occurs within minutes to several hours of exposure. When the symptoms are severe, it is known as anaphylaxis. A food intolerance and food poisoning are separate conditions, not due to an immune response.

Allergen immunotherapy Medical treatment for environmental allergies

Allergen immunotherapy, also known as desensitization or hypo-sensitization, is a medical treatment for environmental allergies, such as insect bites, and asthma. Immunotherapy involves exposing people to larger and larger amounts of allergen in an attempt to change the immune system's response.

Peanut allergy Type of food allergy caused by peanuts

Peanut allergy is a type of food allergy to peanuts. It is different from tree nut allergies, because peanuts are legumes and not true nuts. Physical symptoms of allergic reaction can include itchiness, hives, swelling, eczema, sneezing, asthma attack, abdominal pain, drop in blood pressure, diarrhea, and cardiac arrest. Anaphylaxis may occur. Those with a history of asthma are more likely to be severely affected.

Soy allergy Type of food allergy caused by soy

Soy allergy is a type of food allergy. It is a hypersensitivity to ingesting compounds in soy, causing an overreaction of the immune system, typically with physical symptoms, such as gastrointestinal discomfort, respiratory distress, or a skin reaction. Soy is among the eight most common foods inducing allergic reactions in children and adults. It has a prevalence of about 0.3% in the general population.

Allergic bronchopulmonary aspergillosis (ABPA) is a condition characterised by an exaggerated response of the immune system to the fungus Aspergillus. It occurs most often in people with asthma or cystic fibrosis. Aspergillus spores are ubiquitous in soil and are commonly found in the sputum of healthy individuals. A. fumigatus is responsible for a spectrum of lung diseases known as aspergilloses.

Nambudripad's Allergy Elimination Techniques (NAET) is a form of alternative medicine which proponents claim can treat allergies and related disorders. The techniques were devised by Devi Nambudripad, a California-based chiropractor and acupuncturist, in 1983, drawing on a combination of ideas from applied kinesiology, acupuncture, acupressure, nutritional management, and chiropractic methods.

Milk allergy Type of food allergy caused by milk

Milk allergy is an adverse immune reaction to one or more proteins in cow's milk. When allergy symptoms occur, they can occur rapidly or have a gradual onset. The former may include anaphylaxis, a potentially life-threatening condition which requires treatment with epinephrine among other measures. The latter can take hours to days to appear, with symptoms including atopic dermatitis, inflammation of the esophagus, enteropathy involving the small intestine and proctocolitis involving the rectum and colon.

Egg allergy Type of food allergy caused by eggs

Egg allergy is an immune hypersensitivity to proteins found in chicken eggs, and possibly goose, duck, or turkey eggs. Symptoms can be either rapid or gradual in onset. The latter can take hours to days to appear. The former may include anaphylaxis, a potentially life-threatening condition which requires treatment with epinephrine. Other presentations may include atopic dermatitis or inflammation of the esophagus.

Skin allergy testing comprises a range of methods for medical diagnosis of allergies that attempts to provoke a small, controlled, allergic response.

Phadia develops, manufactures and markets blood test systems to support the clinical diagnosis and monitoring of allergy, asthma and autoimmune diseases. The company is headquartered in Uppsala, Sweden. It has been owned by Thermo Fisher Scientific since 2011.

Allergy testing can help confirm or rule out allergies and consequently reduce adverse reactions and limit unnecessary avoidance and medications.

Alain de Weck Swiss Scientist in Allergy and Clinical Immunology

Alain L. de Weck,, was a Swiss immunologist and allergist. His main scientific contributions were in the area of characterization and prevention of drug allergy. He was the founding director of the Institute of Clinical Immunology at the University of Bern from 1971 to 1993 and authored or co-authored over 600 peer-reviewed publications. He is the recipient of a number of patents that led to commercial allergy products and services. He served as president of international scientific organizations such as the International Union of Immunological Societies (IUIS) and the International Association for Allergy and Clinical Immunology (IAACI) and was founder and later CEO of the Centre Médical des Grand-Places (CMG) company, acquired by Heska of Fort Collins in 1997. In later years he continued his research at the University of Navarra in Spain and wrote on a wide range of topics such as the distinction between science and pseudo-science, the emergence of genetically modified organisms (GMOs) and comparative health care policy.

Alpha-gal allergy — or mammalian meat allergy (MMA) — is a type of meat allergy characterized by a delayed onset of symptoms after ingesting mammalian meat and resulting from past exposure to tick bites. It was first reported in 2002. Symptoms of the allergy include rash, hives, nausea or vomiting, difficulty breathing, drop in blood pressure, dizziness or faintness and severe stomach pain.

Cross-reactive carbohydrate determinants (CCDs) play a role in the context of allergy diagnosis. The terms CCD or CCDs describe protein-linked carbohydrate structures responsible for the phenomenon of cross-reactivity of sera from allergic patients towards a wide range of allergens from plants and insects. In serum-based allergy diagnosis, antibodies of the IgE class directed against CCDs therefore give the impression of polysensitization. Anti-CCD IgE, however, does not seem to elicit clinical symptoms. Diagnostic results caused by CCDs are therefore regarded as false positives.

Rice allergy is a type of food allergy. People allergic to rice react to some rice proteins after they eat rice or breathe in rice steam. Although some reactions might lead to severe health problems, doctors can diagnose rice allergy with many methods and help allergic people to avoid reactions.

Shellfish allergy Type of food allergy caused by shellfish

Shellfish allergy is among the most common food allergies. "Shellfish" is a colloquial and fisheries term for aquatic invertebrates used as food, including various species of molluscs such as clams, mussels, oysters and scallops, crustaceans such as shrimp, lobsters and crabs, and cephalopods such as squid and octopus. Shellfish allergy is an immune hypersensitivity to proteins found in shellfish. Symptoms can be either rapid or gradual in onset. The latter can take hours to days to appear. The former may include anaphylaxis, a potentially life-threatening condition which requires treatment with epinephrine. Other presentations may include atopic dermatitis or inflammation of the esophagus. Shellfish is one of the eight common food allergens, responsible for 90% of allergic reactions to foods: cow's milk, eggs, wheat, shellfish, peanuts, tree nuts, fish, and soy beans.

References

  1. ↑ NIH Guidelines for the Diagnosis and Management of Food Allergy in the United States. Report of the NIAID- Sponsored Expert Panel, 2010, NIH Publication no. 11-7700.
  2. ↑ Cox, L. Overview of Serological-Specific IgE Antibody Testing in Children. Pediatric Allergy and Immunology. 2011.
  3. ↑ Hamilton R et al. Proficiency Survey-Based Evaluation of Clinical Total and Allergen-Specific IgE Assay Performance. Arch Pathol Lab Med. 2010; 134: 975–982
  4. ↑ UpToDate (http://www.uptodate.com/contents/overview-of-skin-testing-for-allergic-disease?source=search_result&search=skin+testing&selectedTitle=1~150)
  5. ↑ Chinoy B, Yee E, Bahna SL. Skin testing versus radioallergosorbent testing for indoor allergens. Clin Mol Allergy. 2005 Apr 15;3(1):4.
  6. ↑ Holzweber, F. (2013). "Inhibition of IgE binding to cross-reactive carbohydrate determinants enhances diagnostic selectivity". Allergy. 68 (10): 1269–1277. doi:10.1111/all.12229. PMC   4223978 . PMID   24107260.
  7. ↑ Boyce J et al. Guidelines for the Diagnosis and Management of Food Allergy in the United States: Report of
  8. ↑ Wood R; et al. (2007). "Accuracy of IgE antibody laboratory results". Ann Allergy Asthma Immunol. 99 (1): 34–41. doi:10.1016/s1081-1206(10)60618-7. PMID   17650827.
  9. ↑ Wang J, Godbold JH, Sampson HA (2008). "Correlation of serum allergy (IgE) tests performed by different assay systems". J. Allergy Clin. Immunol. 121 (5): 1219–24. doi:10.1016/j.jaci.2007.12.1150. PMID   18243289.
  10. ↑ American Academy of Allergy, Asthma, and Immunology, "Five Things Physicians and Patients Should Question" (PDF), Choosing Wisely: an initiative of the ABIM Foundation , American Academy of Allergy, Asthma, and Immunology , retrieved August 14, 2012{{citation}}: CS1 maint: multiple names: authors list (link)
  11. ↑ Cox, L.; Williams, B.; Sicherer, S.; Oppenheimer, J.; Sher, L.; Hamilton, R.; Golden, D. (2008). "Pearls and pitfalls of allergy diagnostic testing: Report from the American College of Allergy, Asthma and Immunology/American Academy of Allergy, Asthma and Immunology Specific IgE Test Task Force". Annals of Allergy, Asthma & Immunology. 101 (6): 580–592. doi:10.1016/S1081-1206(10)60220-7. PMID   19119701.
  12. ↑ WebMD > Medical Dictionary > radioallergosorbent test (RAST) Citing: Stedman’s Medical Dictionary 28th Edition. Copyright 2006
  13. ↑ NIAID-Sponsored Expert Panel (December 2010). "Guidelines for the Diagnosis and Management of Food Allergy in the United States: Report of the NIAID-Sponsored Expert Panel". The Journal of Allergy and Clinical Immunology. 126 (6): S1–S58. doi:10.1016/j.jaci.2010.10.007. PMC   4241964 . PMID   21134576 . Retrieved 30 August 2012.
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