What are the other Names for this Test? (Equivalent Terms)
- Allergy Screen Blood Test
- Enzyme-Linked Immunosorbent Assay (ELISA)
- RAST (Radioallergosorbent Test)
What is Allergy Blood Testing? (Background Information)
- IgE is a type of antibody produced in susceptible individuals, in response to certain food, pollens, drugs, animal dander, dust mites, etc. These antibodies are mostly found in the skin, lungs, and mucous membrane
- On subsequent exposure to specific allergens, specific IgE antibodies trigger mast cells and other cells to release chemicals, like histamine, which produces the signs and symptoms of an allergic reaction
- Allergy Blood Testing can identify allergen-specific immunoglobulin E (IgE) that triggers allergic reactions. The test measures and detects the amount of allergen-specific antibodies in blood
- These tests are referred to as immunoassay tests, such as:
- Enzyme-Linked Immunosorbent Assay (ELISA)
- Radioallergosorbent Test (RAST)
What are the Clinical Indications for performing Allergy Blood Testing?
Following are the clinical indications for performing an Allergy Blood Testing:
- The following symptoms may be experienced by an individual on an acute or chronic basis, which might lead the healthcare provider to suspect an allergy:
- Nasal congestion
- Abdominal pain
- Red itchy eyes
- The test may also be ordered by a healthcare provider to monitor the effectiveness of treatment; the treatment may be stopped, when the individual no longer shows allergic signs and symptoms
How is the Specimen Collected for Allergy Blood Testing?
Following is the specimen collection process for Allergy Blood Testing:
Sample required: Blood
Process: Insertion of a needle into an arm vein.
Preparation required: No special preparation is needed prior to the test.
What is the Significance of Allergy Blood Testing Result?
The significance of Allergy Blood Testing is explained:
- The sensitivity of the test ranges from 60-95% and the specificity from 30-95%. So this test can have both false-positive results (due to non-specific binding of antibody) and false-negative results, even though the individual has an allergic condition
- Negative test result usually means: The individual probably does not have an allergy to that specific allergen. The healthcare provider interprets the results based on other clinical findings and tests
- Elevated (increased) test result usually means: The individual possibly has an allergy; though, additional tests and the individual’s clinical history may be necessary to confirm a diagnosis
The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.
Additional and Relevant Useful Information:
- Allergy Blood Testing may be used as an alternative, especially when allergy skin testing cannot be performed for reasons, like:
- Skin diseases (dermatitis, eczema, psoriasis, etc.)
- Use of certain medications (histamines, steroids, etc.) which may affect the test results
- Severe reaction in the past to skin testing (anaphylaxis)
- Certain medical conditions, such as heart disease, asthma, etc.
- The healthcare providers will seek additional blood tests that may indicate an ongoing allergic process, such as a complete blood count (CBC), white blood cell differential, and total IgE level. Such blood tests may indicate an allergy; though, the results may be abnormal for other reasons too. Hence, clinical correlations with signs and test results are necessary
Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.
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References and Information Sources used for the Article:
http://labtestsonline.org/understanding/analytes/allergy/tab/test/ (accessed on 08/17/2014)
http://www.lifelabs.com/Lifelabs_BC/Patients/MedicalConditions/Blood_Testing_for_Allergies_(SAIGE).asp (accessed on 08/17/2014)