The ISAC Panel Testing

What is an Allergy?

Many people experience symptoms of an allergy or hypersensitivity. The body becomes allergic to something when the immune system becomes over-reactive to a typically harmless substance that does not cause a reaction in most people. The immune system perceives the substance (called an allergen) to be harmful, and so produces antibodies (called immunoglobulin E or IgE) to fight that particular antigen. The person is now sensitised to that allergen so every time contact is made with that allergen, the immune system responds and allergy symptoms develop.

Symptoms usually occur within minutes, typically involving the airways, gut and skin. Allergies can be caused by many types of substances, such as foods (e.g., nuts, wheat, eggs, milk, seafood), pollen (e.g., tree and grass pollen), pet dander (e.g., cats and dogs), dust mites, insect stings (e.g., wasps and bees), moulds, and medicines (e.g., penicillin).

There can be a cross reaction between allergens, whereby an allergy to one substance can results in an allergy to a different substance, such as between tomatoes and peanuts, and apples and birch tree.

Common allergy symptoms affecting the:

• airways include blocked/runny nose, sneezing, coughing, throat constriction, wheezing, and breathlessness, and may result in asthma; itchy red watering eyes are also common. An example is hay fever (allergic rhinitis)
• gut include swelling of the tongue and throat, nausea, vomiting, abdominal pain/cramps, diarrhoea, and abnormal bowel movements. An example is cow's milk
• skin include hives (urticaria), red itchy rash, peeling skin and dermatitis, and lead to eczema.

While some allergies typically affect the airways only, others such as cow's milk and peanut allergies may affect the airways, gut, and skin.

Allergies vary in their ability to interfere with every-day life, ranging from a not-serious mild reaction to a severe and life-threatening serious reaction. Although uncommon, such severe reactions known as anaphylaxis cause itchy skin rash, swelling of the face, hands and feet, wheezing, gut problems, low blood pressure, collapse, and unconsciousness can occur.

What is an ISAC Panel test?

The ImmunoCAP Immuno-Solid phase Allery Chip or ISAC Panel is able to test for 112 components from 51 different allergens all at once. The test works by allowing any IgE antibodies in the patient's blood sample to attach to test allergens. If the person has an allergy, Any IgE antibodies+allergen complexes are then detected by a computer.

The ISAC Panel includes components in foods and air-borne substances (e.g., pollen, animal dander, moulds and mites) that commonly cause allergies, as well as components that cause cross-reactivity between substances.

The ISAC allergy panel is the successor to a technique known as RAST, which is sometimes still used to describe this type of allergy testing.

Why is an ISAC Panel test important?

If you are allergic to something, then its important to understand what component(s) of the substances you are allergic to. One component may cause a temporary mild reaction whereas another may cause a serious anaphylactic reaction. The ISAC Panel test identifies the substances and the substance's components that a person is allergic to. Also, there is only a small chance of incorrect results, whereby test results indicate an allergy but are negative (a false positive) or do not indicate an allergy and are positive (a false negative). False positives disrupt daily life with food restriction and by causing undue stress, while false negatives may cause a serious threat to a person's life. The one-step testing process means that a doctor can suggest ways of managing and living with the allergy.

Who should have an ISAC Panel test?

A doctor will suggest an ISAC Panel test if you have symptoms involving the airways, gut and/or skin, such as those mentioned above. The results of the ISAC Panel test are not affected by your diet or by antihistamine medicines at the time that the test is carried out, and there is no need to fast.

Thus, an ISAC Panel test is considered to be more suitable than an allergy skin test in certain situations. These include when you cannot stop a medicine that may interfere with the test results, if you have a skin problem that may interfere with the accuracy of the test results or you get hives if you scratch your skin, or if there is any risk of the test allergens causing a serious allergic reaction. Additionally, because of the risk of a serious allergic reaction, the ISAC Panel test may be chosen instead of a 'challenge' test that involves giving suspect allergens at increasing doses to a person who is then monitored closely.

How to test for an Allergy with the ISAC Panel test?

The ISAC Panel tests for 112 allergen components using a few blood drops. A test kit provided by The Online Clinic, complete with step-by-step instructions enables you to collect the blood sample at home. Briefly, a few drops of blood are collected by pricking the tip of your little finger. Blood drops are collected up to the top line of a collection tube. If one little finger does not give sufficient blood, then the other little finger tip is used to complete the sample. Once the cap is put on the collection tube, the tube must be inverted carefully several times. The collection tube is then labelled, placed in the packing wallet and posted. The ISAC Panel test results are sent to the doctor requesting the test, who will then explain your results to you. If you have allergies, knowing what you are allergic to will help you to avoid the substance(s).

What are normal ISAC Panel test results?

For the ISAC Panel test, allergens are added to a patient's serum (the clear fluid in blood that contains antibodies including IgE). The amount of IgE antibodies that have bound to each of the 112 specific allergen components are measured.

Each IgE-antibody is specific (known as specific IgE or sIgE) for an allergen component.

The results are reported in standardised units for specific IgE (ISU-E), and these are shown on a 4-point scale:

• Negative or indeterminate: IgE levels less than 0.3 ISU-E
• Low: IgE levels 0.3–0.9 ISU-E
• Moderate: IgE levels 1–14.9 ISU-E
• High: IgE levels higher than 15 ISU-E

How to minimise the risk of allergy symptoms

Up to the age of 6 months, babies should be fed breastmilk only or with hydrolysed milk formulas. From around 6 months, the advice is to introduce foods including those known to cause allergic reactions (such as cow's milk and egg), but only one at a time and in small quantities. This allows you to identify the food if there is an allergic reaction. Parents may get some idea of potential allergies developing in their child from those that they have, because allergies can be hereditary.

Once you know what triggers an allergic reaction, you can avoid it. An allergic reaction to a food can be prevented by checking in food labels and ingredients for the allergen, and by telling restaurant staff when eating out. It is difficult to avoid a family pet, so ensure it is clean and groomed because the allergy tends to be to its dander, urine and/or saliva. Similarly, insect stings and bites may be difficult to avoid, but can be minimised by using insect repellents and covering skin. Dust mites are found all around the home, including in beds, fabric furniture, curtains, carpets, and soft toys, living off human dead skin cells and thriving in humid conditions. Washing bed linen; vacuuming carpets (or opt for wooden or tiled flooring), furnishings and toys; wiping surfaces, and ventilate rooms and/or use air filters. Allergic reactions to pollen tend to be seasonal, such as worse during spring for tree pollen allergies. Weather reports may detail pollen counts since climate affects the release of pollen. Remaining indoors when pollen counts are high, wearing sunglasses, and spreading Vaseline around nostrils may help. Allergies to moulds can be controlled by keeping rooms dry and well-aired to prevent growth of spores.

Knowing the allergen enables a doctor to discuss possible therapies. Antihistamines, decongestants, lotions/creams, and steroids can be effective medicines to control symptoms. Allergen immunotherapy (previously called desensitisation) is used to increase tolerance to the allergen. Allergen extracts are given regularly to the person, and often require supervision by a doctor.

Anaphylaxis requires immediate treatment with adrenaline, followed by calling an ambulance. If you are at risk of anaphylaxis, then the doctor will prescribe adrenaline auto-injectors. These must be with you at all times and used at the start of signs of a severe allergic reaction. Adrenaline is fast acting and acts by opening the airways, raising blood pressure, reducing swelling, alleviating itching, and relieving gut symptoms.