Reading your allergy test: what do class 2, class 6, and the IgE value mean?

You've had an allergy test, and it shows something like "class 3" or "IgE 12.4 kU/l". The result often comes in before you speak to your GP, and then you start searching. This article explains what those numbers mean — and especially what they don't mean.

Beforehand: only your GP or allergist can interpret a result in combination with your symptoms and medical history. What follows is general information, not an assessment of your situation. Always discuss the result with your doctor.

What is being measured

A blood test measures specific IgE: antibodies that your immune system has produced against a certain allergen. For dust mites, this usually involves Dermatophagoides pteronyssinus (abbreviated d1) and Dermatophagoides farinae (d2), the two species most common in European homes.

The result is given in kU/l and is often translated into a class from 0 to 6. This class classification is nothing more than a scaling of the measured value:

• Class 0 — below approximately 0.35 kU/l: no demonstrable specific IgE
• Class 1 — approximately 0.35 to 0.7: low, borderline area
• Class 2 — approximately 0.7 to 3.5
• Class 3 — approximately 3.5 to 17.5
• Class 4 — approximately 17.5 to 50
• Class 5 — approximately 50 to 100
• Class 6 — above approximately 100

The 0.35 kU/l that you often see is the usual lower limit above which a laboratory speaks of demonstrable sensitization. Threshold values and reference values may differ slightly per laboratory, so always read the accompanying reference column and not just the number.

The biggest misunderstanding

A higher class does not automatically mean more severe symptoms. That is the most common misconception when reading such a result.

The test shows sensitization: your body has produced antibodies. Whether you actually experience symptoms from it, and how severe, depends on much more — how much allergen is in your home, whether you also have asthma or eczema, or if other allergies are involved. People with class 5 can have mild symptoms, and people with class 2 can have severe ones.

Therefore, the result is only meaningful in conjunction with your symptom pattern. A doctor looks at both.

What the class is worth then

It is particularly useful as confirmation of a suspicion. If you have symptoms all year round that are worse in the morning, improve when you are away for a week, and worsen in the autumn — then a positive dust mite test fits that picture and you know where to focus your measures.

Conversely, a negative result can prevent you from spending months cleaning up the wrong problem.

Why the result does not change with your clean-up efforts

People often ask this: if I tackle everything, will my value go down? Usually not quickly, and it is not the goal either. IgE values generally decrease slowly and are not a good indicator of the effect of measures at home.

What you do aim for is your exposure. Less allergen in your mattress, sofa, and bedding means you will less often exceed the threshold at which you experience symptoms. You will notice this in how you wake up, not in a number in your file.

Where your exposure is

The largest reservoir is your mattress, followed by your pillow and duvet, and then your sofa. What fits in the washing machine, you wash weekly at 60°C. What doesn't fit in there must be mechanically cleaned — and then it is especially important whether the device also retains the allergen.

We had the filter medium of the MiteMaster® independently tested according to EN 1822: 99.97% capture at the most difficult to capture particle size. You can read the measurement data and the report number. In addition, it helps to keep the humidity below 50%.

Take this to your appointment

If you go to your GP with the result, it helps to write down beforehand: when the symptoms occur, whether they stay away if you sleep elsewhere, whether there is shortness of breath or eczema, and what you have already tried. That makes the conversation a lot more targeted than just the number.