Choosing an Allergy Test : The Lowdown

While there are many allergy tests to choose from, there are only three that should be considered. The Skin Prick Test (SPT), the IgE blood test and the oral food challenge (OFC) are the only allergy tests that are medically verified and approved. There is no doubt that “allergies” and all that they entail are vast money-spinners, and some tests fail to put accuracy or even patient safety above generating income.

Globally speaking around 2% of the adult population and 5% of the paediatric population are effected by allergies — be it food, environmental, or both. The diagnosis of “allergy” is hard hitting, and has a huge impact on the allergy sufferer’s life.

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Allergies are life changing, and they are not easy to deal with. This is why accurate and safe allergy testing is so important. If you suspect that you yourself or your child has an allergy, you need to know what you are dealing with.

As Dr Chiang of KK Women’s and Children’s Hospital states, “Accurate diagnosis of food allergy in children is of the utmost importance. Inappropriate food elimination is just as harmful.” The other possible consequence of inappropriate allergy testing may also mean that relevant and potentially life-saving medical equipment such as the EpiPen or antihistamines are not carried by the sufferer when they should be.

Allergy tests that are medically verified and approved can seem expensive: a SPT costs about $150, the IgE $200, and the OFC $400. However, this is money well spent if you and your doctor suspects allergies. The other (unverified) tests out there can be as accurate as “eeny, meeny, miny, mo”, which is about as cost effective as throwing your money down the drain.

Although the name may suggest otherwise, the SPT is not actually painful. A small drop of the ‘allergen’ is placed on the skin and the tip of a lancet is used to prick the skin through the allergen. It is possible to test for multiple allergies, up to 25, in one sitting. If the result is positive there will be a visible reaction on the skin in the form of a raised reddish weal or welt. Results will be given on that day. Any reaction needs to be interpreted by a doctor and if necessary followed up with either an IgE blood test or an OFC.

During the IgE blood test (sometimes referred to as a RAST test and not to be confused with the IgG blood test), blood is taken from the patient and is then sent to a laboratory for analysis. The presence and levels (if any) of the allergen-specific IgE antibody will allow the doctors to confirm or dismiss the potential allergy. Although this test can analyze hundreds of potential allergies in one go, it is usually unnecessary to run the whole battery of allergens; your doctor would choose the most appropriate ones depending on the clinical history. This test is also very useful in monitoring the allergy for signs of improvement or an increase of IgE levels to a specific allergen.

Dr Lee Bee Wah from Mount Elizabeth Medical Centre adds, “Allergy skin or blood tests can help in the diagnosis of immediate (also known as IgE) allergy to food and inhalants. It is also useful for the monitoring of food allergy”.

The third medically-verified and accepted method of diagnosing allergies is through an Oral Food Challenge (OFC). The patient will be given a small amount of the suspected allergen to eat, and the reaction will be used to determine whether there is an allergy or not.

This test is never to be carried out at home, and must always be given under the care of a relevant qualified doctor who has the necessary medical equipment at hand in case of any adverse reaction. This test is usually carried out if the results of the SPT or the IgE blood test are ambiguous.

Any of the other so-called allergy tests out there are not medically approved, verified or reliable. “Unfortunately there are many laboratories around the world, including Singapore, that offer allergy testing that is not scientifically validated. Some have been disproven. Doing such tests may be misleading,” Dr Lee Bee Wah cautions.

Below is a summary of the common allergy tests available that have not been verified.

* IgG blood test.
The IgG blood test looks for food-specific IgG, and measures the IgG antibodies to various foods. IgG can be found in people without evidence of food allergies, and there is no clinical evidence to support a link between food allergy and food-specific IgG levels.

* Electrodermal Testing (sometimes called VEGA testing)
This is a form of modified electro-acupuncture that is used to determine allergies based on the skin’s ability to conduct electricity when exposed to the allergen. In a recent study titled ‘Food Allergy Diagnosis’, Doctors Beyer and Teuber stated: “We still conclude that electrodermal testing cannot be recommended for the diagnosis of food allergy, since it is without established scientific basis”.

* Applied Kinesiology
The patient is asked to hold a sealed container (with the allergen inside) in one hand, whilst the practitioner tests the strength of the other arm, and with any sign of weakness the allergy is diagnosed. Beyer and Teuber’s report confirmed that “kinesiology as a diagnostic tool is no better than random guessing”.

* Cytotoxic Test
A drop of blood is added to a dried sample of the suspected allergen — any changes in the food particle and an allergy is diagnosed. This test has been debunked by all medical literature surrounding it.

* Chemical Testing
Various bodily tissues and fluids are tested for a wide range of substances such as heavy metals, pesticides, organic solvents, minerals and cytokines. It is a long list. The theory is that people with high levels of these chemicals have a damaged immune system, and therefore have a predisposition towards allergies. Not medically verified and approved.

* Bioresonsance testing
This test measures the body’s electromagnetic energy and is reported to assess one’s current health status, food intolerances, vitamin/mineral deficiencies and chemical toxicity. There is no scientific basis for this form of testing, which can apparently test for various health problems. It is not endorsed by academic professional bodies.

* Allergy Testing “Home Kits”
Avoid home testing allergy kits. These can be dangerous and highly misleading. They do not use the medically verified and approved ways of testing for allergies. Results always need to be interpreted by a doctor.

Vicky Henniker-Anandraj is the editor of sneezywheezy.com, Singapore’s only allergy blog.

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