Skin Prick Test (SPT) vs Blood Allergy Tests: Which is better for diagnosis of allergy?

Allergies occur when our immune defence system overreacts to something in the environment. These substances are called “allergens”. This reaction of our body leads to various problems in our body. The common body parts involved in allergy are the skin, eyes, nose, sinuses and lungs.

When is an allergy test required?
Allergy testing is required in children or adults if they are suffering from nasal allergy or allergic rhinitis, recurrent wheezing or asthma, eye allergy or allergic conjunctivitis, food allergy and anaphylaxis.

What are the various methods to identify the cause of allergies?
Skin Prick Tests (SPT) and blood allergy tests are the two methods used to identify the cause of the allergies. The other methods are intradermal skin testing, allergy patch tests and challenge tests which are uncommonly used.

What are the various allergens for which allergy testing can be done?
Allergy testing can be done for four groups of allergens: aeroallergens or allergens in the environment, food allergens, drugs and insect venom. The most commonly performed allergy tests are for aeroallergens and food allergens. The common indoor aeroallergens are dust mites, pet dander, moulds and cockroaches while the common outdoor aeroallergens are pollen of trees, weeds and grasses.

How accurate is Skin Prick Tests (SPT) allergy testing?
Skin Prick Tests (SPT) is the most common allergy test performed across the world for diagnosis of various allergies. Skin Prick Tests (SPT) are accurate and inexpensive ways to confirm allergens. Skin Prick Tests (SPT) are simple to perform, safe and quick tests, providing results within 15-20 minutes.

Skin Prick Test (SPT) vs Blood Allergy Tests

Skin Prick Tests (SPT) is performed on the inner forearm, but occasionally done on the upper back. Multiple allergens can be simultaneously tested in Skin Prick Tests (SPT). These depend on the condition and can vary from 4-5 or upto 25 allergens. A small drop of each allergen is placed on the skin and then pricked with a special lancet through the drop.

If the person is allergic to that allergen he will develop a localized allergic response in the form of swelling (bump/wheal) redness, and itching at the site of testing within 10-15 minutes. The larger the wheal size, the more likely is the person being allergic to the allergen. Skin Prick Tests (SPT) can be done at any age including babies.

Are allergy blood tests accurate?
Blood tests are the other way to identify the causative allergens leading to allergies. Blood is tested in the laboratory for the presence of IgE antibodies against various allergens like aeroallergens and food allergens. Various blood tests are available in the market but all are not the same. The sensitivity and specificity of these various blood tests is quite variable. The latest and the most advanced system is the ImmunoCap from thermo fisher and gives precise results.

Finally, Skin prick tests (SPT) may be more sensitive and specific than blood allergy tests for diagnosis of allergy, though both methods are considered accurate. If your child is suffering from any allergies get in touch with a pediatric allergist and get proper diagnosis of your allergy.

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