What Happens During An Allergy Blood Test
An allergy blood test only takes a few minutes. A healthcare provider called a lab technician usually takes blood samples in your doctors office or a lab.
Heres what you can expect:
- The phlebotomist takes blood from a vein in your arm using a thin needle.
- The needle might cause a mild pinch and some discomfort.
- The phlebotomist fills a collection tube with blood and then removes the needle.
- They place a small bandage on your arm.
When Should The Immunocap Blood Test Be Administered
A doctor will typically order this blood test when the symptoms of an allergy appear outside of the normal allergy season. Someone who has repetitive visits for upper respiratory distress will often have this blood test ordered, as will some people who have asthma or similar symptoms that suddenly appear and cannot be explained.
As If All Of This Doesnt Make The Meaning Of Blood Ige Numbers Confusing Enough Being Sensitized To An Allergen Does Not Even Necessarily Mean You Are Allergic
So the presence of IgE in the blood suggests that you are sensitized, but does not guarantee it. And being sensitized suggests that you are allergic, but does not guarantee it?? That makes blood IgE results at least 2 important steps removed from a diagnosis of allergy.
Being defined as allergic to an allergen means that there is enough clinical and/or test evidence to suggest that in the presence of an allergen, your allergy cells are at a decent risk of being activated causing you to have symptoms. As you can see from this definition, there is really no one type of test that alone would always be able to diagnose an allergy.
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A High Blood Ige Level To An Allergen Doesnt Necessarily Indicate That You Are Allergic And A Low Or Negative Blood Ige Level Doesnt Necessarily Indicate That You Are Not Blood Ige Tests Require Interpretation Within A Much Larger Context To Have Meaning
At Allergenuity Health, we spend the time to collect and carefully consider your medical history, environmental influences, immune system function, and important test-related factors in order to provide you with a thoughtful interpretation of what a specific blood IgE result may mean for you .
We all wish that a negative blood IgE simply meant that you are not allergic, a low blood IgE meant you are only mildly allergic, and a high blood IgE meant you are very allergic. If this was the case, blood IgE would be a great diagnostic test, and tracking blood IgE levels of time would clearly tell us if your allergies were getting worse or better. However, that is unfortunately not the case. Even though this is how blood IgE tests are sometimes used by companies selling allergy treatments and even some providers running these tests, using blood IgE tests this way gives an overly simplistic and possibly incorrect interpretation of what your results mean, and this can lead to misdiagnosis, treatment mismanagement, and a lot of frustration and confusion.
Additionally, commercial tests for blood IgE may also be lacking the ability to detect the exact type of specific IgE that your body has produced towards an allergen because these tests of course cannot measure everything, so they are set up to measure what they can and what is most common.
What Is A Positive Rast Test
Most labs will report the RAST findings on a scale of 0 to 5 or more. A 0 value suggests a low likelihood of an allergy. Positive values mean thereâs a likelihood of an allergy, which increases with a higher number. Some labs report the IgE values in micrograms per milliliter . An experienced allergist will know what this means.
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What Do The Results Of An Allergy Test Mean
Allergy test results may be:
- Negative: You arent allergic to that substance. Its rare to get a false negative allergy test result .
- Positive: Youre allergic to that substance. Note that even when tests correctly show that you have an allergy, it doesnt necessarily mean that youll react to that allergen. A false positive test result is possible, especially from a blood test. A false positive means the results show you have an allergy when you dont.
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Why Allergy Testing Is Performed
Allergies affect more than 50 million people living in the United States, according to the American College of Allergy, Asthma, and Immunology . Inhaled allergens are by far the most common type.
The World Allergy Organization estimates that asthma is responsible for 250,000 deaths annually. These deaths can be avoided with proper allergy care, as asthma is considered an allergic disease process.
Allergy testing can determine which particular pollens, molds, or other substances youre allergic to. You may need medication to treat your allergies. Alternatively, you can try to avoid your allergy triggers.
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What Is It Used For
Allergy blood tests are used to help find out if you have an allergy. There are two general types of allergy blood tests:
- A total IgE test is used to measure the total amount of IgE antibodies in your blood.
- A specific IgE test measures how much IgE your body makes in response to a single allergen. A separate test is done for each allergen that may be causing your allergies.
Why Allergy Blood Tests Are Done
Allergy skin testing is the preferred method, but in some cases blood testing may be ordered.
Allergy blood testing is recommended if you:
- Are using a medicine known to interfere with test results and cannot stop taking it for a few days this would include antihistamines, steroids, and certain antidepressants.
- Cannot tolerate the many needle scratches required for skin testing
- Have an unstable heart condition
- Have poorly controlled asthma
- Have severe eczema, dermatitis, psoriasis, or another severe skin condition
- Might have an extreme reaction during skin testing or have a history of life-threatening allergic reaction called anaphylaxis
Your doctor may also order blood testing to determine how well your allergy treatments are working. Blood testing may also show whether you have outgrown an allergy.
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Why Seek An Allergist
Attempting to self-diagnose food allergies and interpreting results can be challenging. With food allergy tests, false positives and false negatives can occur. For this reason, you should always seek out a board-certified allergist to diagnose and treat your symptoms. Moreover, laboratories use various blood tests with different scoring systems. An allergist, however, is an expert and will be aware of the differences and know how to accurately interpret the results and explain to you what the results mean.
Food allergy testing is an important part of making a diagnosis. However, an allergist has many tools that increase the accuracy of a diagnosis, such as taking into account your medical history, using the elimination diet, and using other methods of food allergy testing .
How Is The Ige Test Performed
A serum IgE test is performed by drawing a blood sample from a vein by inserting a needle which takes a few minutes. The method is safe and fast and you might feel a slight prick while the needle is being inserted. The blood sample is then tested for specific levels of IgE. The blood collection method includes the following steps. The skin around the vein from which blood is collected is cleaned. An elastic band is tied around the area to make the veins swell up with blood. The point chosen is generally around the elbow or at the back of the palm. A needle is inserted in the vein to draw the blood into a connected syringe. The elastic band is taken off and the needle is pulled out from the skin. In the case of some individuals, it can be difficult to find a vein so the healthcare professional may have to try more than once. For babies, blood is often drawn from the heel area through a tiny needle and the method is often termed as heel stick collection.In some special cases, the test is also done through a collection of the cerebrospinal fluid that surrounds the brain and spinal cord. In these cases, an anesthetic shot is administered to prevent any discomfort during the collection. A hollow needle is inserted in the space between two vertebrae in the lower spine to remove a small amount of the fluid.
Why Your Child May Need An Allergen
Your childs doctor may order an allergen-specific IgE test if your child has some or all the following symptoms of an allergy:
- Stuffy or runny nose
An allergen-specific IgE blood test may be used in addition to or instead of skin testing. IgE blood tests are often used when children have a skin condition that may interfere with skin testing or cannot stop taking their antihistamines.
What Is The Immunocap Specific Ige Blood Test
A laboratory test to rule in or rule out atopy in patients with allergy-like symptoms. ImmunoCAP provides a clinically-relevant means of confirming or excluding the presence of atopic disease in patients with upper respiratory disease. These allergy-like symptoms are very difficult to differentiate. ImmunoCAP will also accurately identify specific allergen sensitivities in patients with confirmed allergy.
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Pros And Cons Of Allergy Blood Tests
Advantages of allergy blood tests include:
- Can be done at any time, regardless of any medications you are taking
- Requires only one needle stick this may be more attractive for people who are afraid of needles. Allergy blood testing is the preferred test for infants and very young children.
Disadvantages of allergy blood tests include:
- More expensive than skin testing many health insurers do not cover allergy blood tests.
- May be less sensitive than skin tests
- Takes days or weeks to get results because the blood sample must be sent to a laboratory for evaluation skin testing provides immediate results.
Is The Ige Test Safe During Pregnancy
There are no restrictions on pregnant women from undergoing an IgE test. Many pregnant women suffer from allergies like rhinitis, asthma, conjunctivitis, acute urticaria, anaphylaxis, food allergy, and drug allergy. The correct monitoring of these conditions is necessary for the health of the mother and the baby.
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How The Test Is Done
Doctors often measure IgA, IgG, and IgM together to get a snapshot of your immune function. A lab tech will usually take a sample of your blood by inserting a needle into a vein in your arm. The blood collects into a tube or vial.
Another way to do this test is with a sample of whatÃ¢â¬â¢s called cerebrospinal fluid .
CSF surrounds your brain and spinal cord. The doctor will take a sample of this fluid with a lumbar puncture .
For this, you go to an outpatient facility or a hospital. A technician will give you a shot in your back to help numb any pain.
You will likely lie on your side with your knees pulled up to your chest, or you sit on a table. The technician inserts a hollow needle between two vertebrae in your lower spine and removes a small amount of fluid so it can be tested.
Total Ige Test Vs Specific Ige Test
While the total IgE test measures the sum of all kinds of IgE in the blood, a specific IgE test looks for particular IgE antibodies that are linked to certain substances or allergens.
Because they measure different things, these two tests have different purposes. A specific IgE test can offer more detailed information about particular immune responses. A total IgE test may provide more information when diagnosing certain conditions and planning treatment for allergic asthma.
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Blood Tests For Antibodies Other Than Ige
Studies in the 1970s found that IgG antibodies can also cause allergic reactions in rodents. Therefore, tests for IgG antibodies that bind to food were developed, because IgG antibodies are very abundant and hence very easy to measure with crude assays such as ELISA. However, IgG antibodies do NOT lead to allergic reactions in human beings. In fact, one of the mechanisms that the body uses to produce immune tolerance is allergen-specific IgG4 antibodies. IgG4 antibodies are immunologically inert, yet they compete with IgE for allergen binding, and since they exist at much higher concentrations, they can effectively block IgE-mediated allergic reactions. Accurate tests that measure allergen-specific IgG4 are useful in determining immunological tolerance, especially during desensitization therapy.
Despite their lack of effectiveness, IgG blood tests are still being heavily promoted for the diagnosis of food allergy and âintoleranceâ. Many patients have been misled by these tests into believing that they have multiple food allergies, and undergo unnecessary and even harmful food avoidance. More ominously, real food allergy remains undiagnosed, leading to fatal or near-fatal accidents. Any laboratory that promotes food IgG tests for diagnosing allergy is perpetrating healthcare fraud.
Characteristics Of Protein Families
24. What do component tests show us?
Allergen components or protein testing, along with a patients medical history can help assess a persons risk for reaction, which versions of the food a patient may tolerate, and/or the probability of a reaction being mild or severe.There are different proteins that make up each allergen, some are much more likely to be higher risk for anaphylaxis and some are not. So understanding the risk profile may dramatically change the way you manage the condition.
25. Can you get component testing for all food allergens?
Component testing is currently available for peanut, cashew, walnut, hazelnut, brazil nut, milk, and egg. More foods, such as wheat and soy are available and ordered in Europe.
26. Do all allergists offer component testing?
Most allergists are likely aware of the option and many allergists order component testing. Inquire about the availability when you are selecting an allergist or before your next visit.
27. Can I request component testing if my allergist doesnt offer it?
Any healthcare provider who can order a standard specific IgE blood test can also order testing for specific protein components. Most major reference labs offer component testing, so even if your local lab does not run them they can send the specimen to a national reference lab that will.
28. Who has to prescribe component testing?
Any healthcare provider qualified to order a lab test can order.
29. Is component testing covered under insurance?
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Clinical Considerations: The Importance Of Diagnostic Testing
Allergy diagnosis based solely on physical examination, clinical observation, and patient history may result in an inaccurate or incomplete diagnosis. But adding diagnostic testing to aid in a differential diagnosis has been shown to increase confidence in diagnosis to 90 percent.9,10
Diagnostic testing can also help in the following ways:11-13
- Improve the patientâs quality of life and productivity.
- Reduce costs associated with absenteeism.
- Optimize use of medication.
- Lower medication costs.
Measurement of circulating IgE antibodies provides an objective assessment of sensitization to an allergen. In general, low IgE antibody levels indicate a low probability of clinical disease whereas, high antibody levels to an allergen show good correlation with clinical disease.14
Negative test results may enable healthcare providers to rule out IgE-mediated allergy altogether as a cause of a patientâs symptoms, better enabling them to steer the treatment path, medication, and management in the correct direction.9,10
Understanding Food Allergies Vs Food Sensitivities
There are important differences between food sensitivities and food allergies. Different arms of the immune system facilitate both conditions. Food allergies are immediate, potentially life-threatening, mast-cell mediated, and often involve IgE antibodies, whereas food sensitivities are delayed reactions and elicit IgG antibodies.
It is best practice to measure IgE and IgG antibodies together as they independently create inflammation and play a role in symptoms driven by food. A food can elicit an IgE sensitivity response, an IgG antibody response, or both.
|Immediate reaction that can occur within minutes of exposure||Delayed reaction that can occur several hours to 3 days after exposure|
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Additional And Relevant Useful Information:
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 you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.
The following DoveMed website link is a useful resource for additional information:
Do Allergy Blood Tests Ever Deliver False
About 50% to 60% of all allergy blood tests give false-positive results. False-positive results show you have an allergy even when you dont. Sometimes false positives happen if your body is reacting slightly to substances in certain foods youve eaten recently.
A note from Cleveland Clinic
An allergy blood test checks your blood for certain antibodies that increase if you have an allergy. Your healthcare provider might order one if you have a skin condition, take antihistamines or cant have a skin allergy test for any reason. Its important to remember that allergy blood tests often deliver false-positive results and they cant determine the severity of an allergy. If you have an allergy, talk to your provider about ways to reduce your risk of an allergic reaction.
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Blood Tests Vs Skin Tests
Both the blood test and the skin prick tests detect food-specific IgE. With the skin tests, the result is immediate, but the blood test result will take at least several days to arrive. Unlike the skin prick test, the blood test is not affected by antihistamines and can be performed for people with extensive rashes that prevent using skin tests.