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Diagnosing Allergies
Diagnosing Allergies

Serum Allergy Testing

The serum allergy test is one type of allergy test that can be used to assist in the diagnosis and management of allergies. Through a simple blood test, analyzed in a laboratory, your doctor can uncover the amount of allergen-specific antibodies, called Immunoglobulin E (IgE), in your blood to help detect allergies to a variety of substances. IgE testing can also be used to monitor patients with an existing allergy diagnosis.

How is the test performed?

Blood Sample

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Have you ever experienced itchy/watery eyes, a runny/itchy nose and sneezing, or a rash that appeared out of nowhere? If so, you could be having an allergic reaction to a substance that is ordinarily harmless to most people. Allergies happen when your immune system mistakenly interprets a foreign substance (called an allergen), like dust, pollen, bee venom, latex, animal dander and certain foods and medications, as harmful and produces antibodies in reaction to it. As a result, when your body is exposed to the allergen for the first time, you become sensitized.

The extent to which allergy symptoms are experienced is different from person to person with the same allergy, and the reaction can range from mild discomfort to a very serious, life-threatening medical emergency, called anaphylaxis.

Allergies are diagnosed by your family doctor or an Allergist. They will consider your symptoms, history, and likelihood of exposures to various allergens. To investigate further they may also include a physical exam and will learn about your family history, lifestyle, and medical history.  

There are two types of allergy tests that can be used to help pinpoint exactly what you’re allergic to.  These are: 

  1. Skin test (either scratch or patch test) 
  2. Blood test (serum allergy test) 

The results of your test(s), in combination with your medical history, will be interpreted by your doctor to provide any potential diagnosis.  

To identify the allergen(s) triggering your symptoms, either a skin test (scratch test or patch test) or a simple blood test (called the serum allergy test) may be done. The differences between these types of tests are listed below.

Skin tests 

An allergy skin test is done by an allergy specialist (allergist) and involves exposing your skin to a variety of suspected allergens, like pollen, mold, animal dander, dust mites and food, to observe whether a reaction occurs. A skin test can either be a scratch test or a patch test. With both types of tests, if a positive reaction occurs, like swelling or itching, you may have an allergy to that substance.  

For the scratch test, small droplets of allergy-causing substances are placed on your skin and then the outer-layer of your skin is lightly scratched to allow the allergen to enter. The allergist will then have you wait for 15-20 minutes to monitor for a skin reaction to the substance(s) in question.   

A patch test, on the other hand, involves placing a patch containing the allergens on your arm or back so that the allergens can be absorbed by the skin. This process typically takes 72 hours to complete and will require a return visit to the allergist’s office.  

Blood test 

Through a laboratory analysis of a small blood sample, the serum allergy test measures the amount of allergy-causing antibodies circulating in your bloodstream, which are called immunoglobulin E (IgE) antibodies. If the IgE antibodies of a specific allergen are detected, it may indicate an allergy to that substance. 

Your doctor will use all the information available to them including results of testing (in combination with medical history) to help make the appropriate diagnosis. Because allergies can cause life-threatening reactions, it’s important that you work with your doctor to find the testing and treatment plan that works best for you. 

Although scratch and patch tests are widely used by allergists, a blood test can have many advantages over these skin tests. These include: 

  • A blood test is a quick, non-invasive procedure  
  • Your family doctor can order a serum allergy test
  • For some food-related allergies a serum allergy test can provide more information than a skin test 
  • The results of a serum allergy test are not influenced by any of the medications you may be taking 
  • You are not being exposed to any allergens as part of the test 
  • If you have a skin condition it will not impact your results
  • Because of the non-invasive nature of the blood test, it can be used with infants starting at six-weeks old and up 

Serum allergy testing can be broken into two types of specific tests that can help your doctors identify what you are allergic to.

Primary Allergen Test

A primary allergen test is a blood test that can help identify allergic triggers to help determine whether you have an allergy to specific allergens like pollen, peanuts or milk, for example.

Allergen Component Test

An allergen component test, usually ordered by an allergy specialist, can help pinpoint the proteins within the specific allergen that may be causing your allergy symptoms. So instead of just knowing that you’re allergic to peanuts, you can know exactly which protein within the peanut triggers your reaction. By knowing this information, your allergist can better determine if you may be at risk for a more severe, systemic reaction, like an anaphylactic shock, or a mild, localized reaction like itchy eyes.

For example, when it comes to food allergies, a positive or negative result for allergen components can provide a more in depth understanding of your risk for reaction and could change the way your food allergy is managed. A positive test result to certain peanut proteins could indicate that you are at risk for a systemic reaction, such as anaphylaxis, if peanuts are consumed. Alternatively, a negative test result to certain milk proteins may indicate that a milk-allergic child will not react to milk if it’s altered in a certain way, such as being baked into a cake or cookies.

This is equally applicable for an animal or pet dander allergy. A positive or negative test result to allergen components, could change the way your animal allergy is managed. For example, testing with allergen components can help differentiate between reactions that are caused by a specific species, like cats, and reactions caused by cross-reactive components (similar proteins found in multiple species). This information could impact your decision to get or keep a pet.

Your doctor may order a serum allergy test if you report any of the following signs and symptoms of an allergic reaction, which can vary depending on the substance involved: 

  • Runny, itchy, or stuffy nose and/or sneezing 
  • Itching, watery, red, or swollen eyes 
  • Coughing, tingling, or itching in the mouth 
  • Swelling of the lips, tongue, face, or throat
  • Hives, dermatitis, eczema
  • Shortness of breath, wheezing 
  • Anaphylaxis – a life-threatening medical condition 

Online purchase of serum allergen testing is available to Ontario residents only.

Ontario residents can choose and pay for select allergy tests online. Testing is completed by LifeLabs at a Patient Service Centre or via our mobile lab service (available in select cities) through collection of a blood sample. You will require a completed Allergen Test Requisition from your health care provider. This is a special requisition specifically for allergy testing that is different from the standard OHIP and MSP requisitions. 

For Ontario patients, serum allergy tests are not insured and will need to be ordered and paid for privately. 

You can order a serum allergy test for some common allergens by clicking  here

Residents of BC are advised that serum allergen testing is covered under the MSP program for symptomatic patients, under specific conditions. Please consult your BC health care provider in order to access serum allergen testing. Online purchase of serum allergen tests is available to Ontario residents only.

Individual Allergens 

Test results will be provided directly to your health care provider for discussion with you. Results will be reported numerically for each allergen-specific antibody being measured. 

A result less than 0.35 kU/L means that there is less than 0.35 kU/L of patient IgE in the sample that reacts with the allergen being tested. This could mean there are no IgE in the sample reacting with the allergen, or there are very low levels. This type of result can be consistent with both having an allergy, or not having an allergy to the allergen being tested. 

A result greater than 0.35 indicates the presence of allergen-specific antibodies to the allergen being tested. This type of result does not diagnose an allergy to the allergen being tested. 

It is important to note that understanding blood test results is not straight-forward. They sometimes suggest an allergy when there isn’t one (false-positive) or may not identify something that you are allergic to (false-negative). In addition, blood tests cannot diagnose an allergy. Your healthcare provider will interpret blood test results in the context of your medical history and symptom presentation to arrive at the appropriate diagnosis. 

If the results of your allergen test return a positive result for any of the whole allergens measured, please speak to your health care provider about a referral to an allergy specialist who may order a component allergy test as a next step.

Serum allergy testing involves the quantification of immunoglobulin E (IgE) antibodies. During an initial allergen exposure, a process called sensitization occurs, whereby an allergic person produces specific IgE to certain types of allergens like pollen, pet dander or foods. The IgE associated with that allergen then binds to mast cells prompting the immune system to recognize the allergen and release inflammatory mediators, like histamine, which produces the allergic reaction. 

Types of serum allergy tests available  

  • Total IgE measures the overall quantity of immunoglobulin IgE in the blood. Total IgE can be used to detect an allergic response in the body, however, cannot identify specific allergen antibodies. 
  • Specific IgE measures IgE antibodies associated to individual allergens. Specific IgE tests are performed individually and can identify antibodies for allergens including milk, hazelnuts, or peanuts. 
  • Also available within specific IgE testing is allergen component testing. This is where specific allergen proteins are measured. Allergists may include allergy component testing in their management of patients. Component testing may aid in further targeting of the allergen, understanding symptom risk from the allergen, directing day-to-day management of the patient, or facilitating treatment or allergen reintroduction. Although a general practitioner can include total IgE and specific IgE testing in their initial investigation of an allergy diagnosis, a referral to an allergist may also be necessary to further investigate, manage or treat the patient. 

 

When a patient presents with acute or chronic-like allergy symptoms the serum allergy test, or specific IgE test, may be ordered to help determine specific allergens. Although skin allergy tests, like the scratch and patch tests, are useful, the serum allergy test has many advantages; it is less invasive and can be used when the patient has a skin condition, or if they are on an antihistamine or antidepressant medication. It also eliminates the possibility of anaphylactic shock in those patients where such a risk exists with a skin test.  

Another clinical use for the serum allergy test, is that it can be performed to identify patients that are suitable candidates for immunotherapy testing and to monitor the effectiveness of the therapy. It can also be used to assess whether a child has outgrown an allergy. 

Samples for the serum allergy test may be taken at any of our Patient Service Centres. Patients must have one of the following special allergy requisition forms completed by a physician or health care provider. Please note that it is recommended that allergen component testing be ordered by an allergy specialist. 

In Ontario: 

Allergens click here

Component Allergens click here

In British Columbia: 

Allergens (i.e., SAIGE requisition) click here

Component Allergens click here 

The serum allergy testing price includes the laboratory analysis of the blood sample and the physician interpretation fee of $15.

Whole allergens are priced at $25 per allergen and component allergens range in price from $40 to $150. Please call LifeLabs customer care at 1-877-849-3637 (ON) or 1-855-412-4495 (BC) to obtain more specific fee information on component testing.

Test turnaround time is 2-3 days (from blood sample collection) for primary allergens, and components for peanut, hazelnut, egg (ovalbumin and ovomucoid) and cow’s milk.

For all other allergen components, please allow 4-8 weeks for the results to be reported.

We have a wealth of medical experts available to support you in interpreting test results. Consults with our experts are available upon request. 

    Request more information

    A serum allergy test may be scheduled directly by the patient at any of our Patient Service Centres. They must have a requisition form completed by a physician or health care provider. 

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