Allergy and intolerance
IgE antilichamen pinda
Antibodies against peanut protein; shows whether the immune system is sensitive to peanut, not whether you get symptoms from it.
Everything about this testWhat it measures
This test measures the amount of IgE antibodies against the proteins in peanut in the blood. IgE is the type of antibody that, in an allergic reaction, prompts mast cells to release histamine. The body only makes such antibodies after it has been in contact with the allergen before; this is called sensitization. The result is a number in kU/l; the laboratory states from which value the result counts as positive.
- Sensitization to peanut: the body has made IgE antibodies against peanut
- Support in looking into a suspected peanut allergy, together with the story of the symptoms
- Support in answering whether an earlier reaction after eating peanut fits an allergy
High
A value above the cut-off means you have IgE antibodies against peanut: sensitization. That is not the same as an allergy. Peanut allergy usually starts at a young age and lasts a lifetime in about 3 in 4 people. A positive result is also often caused by cross-reaction: someone who is allergic to birch pollen can have antibodies against peanut proteins and get at most itching in the mouth or throat. In hospital, antibodies against individual peanut proteins are therefore often measured: antibodies against Ara h 2 go with a higher chance of a severe reaction, antibodies against Ara h 8 usually point to a cross-reaction with pollen. According to the Dutch Society for Clinical Chemistry (NVKC), the height of the result says nothing about how severe a reaction would be, although a clearly higher value does go with a higher chance that there really is an allergy.
Low
A value below the cut-off means that no IgE antibodies against peanut were found. A peanut allergy that works through IgE is then a lot less likely. According to the Dutch medical specialists' guideline (FMS), with a negative result the chance of an IgE peanut allergy is negligibly small in the groups studied for this. Symptoms after eating can also have another cause, for example an intolerance or a bowel condition.
If your result is abnormal
The GP mainly looks at the story: which symptoms, how soon after eating and how often. Often a food diary follows, along with temporarily leaving out and then reintroducing the suspected food. If a real allergy is suspected or after a severe reaction, you are referred to an allergist or pediatrician, where a food challenge is done if needed; according to the Dutch medical specialists' guideline (FMS), that test is the gold standard.
Reliability
A positive IgE result shows sensitization, not allergy: it only means there are antibodies, not that you get symptoms from peanut. The pooled specificity of the IgE test for peanut in the Dutch medical specialists' guideline (FMS) is 61 percent: about 4 in 10 of the people studied without a peanut allergy still have a positive result, often due to cross-reactions. Because a positive result also occurs in people without an allergy, the result can cause confusion when looked at apart from the symptoms. The result can only be interpreted together with the story of the symptoms and, in case of doubt, with a food challenge in hospital.
Limitations
- A pollen allergy, especially to birch pollen, often gives a positive result without a real peanut allergy.
- The test measures all peanut proteins together; testing for individual proteins such as Ara h 2 says more about the chance of a severe reaction.
- People with a peanut allergy can also react to soy, peas, lentils, beans or lupin; these are not measured here.
- Laboratories use different measuring methods; results from different labs cannot always be compared one to one.
How common is this
About 1 in 100 children under 5 years old in Western countries has a peanut allergy. In about 3 in 4 it lasts a lifetime; about 1 in 4 outgrows it. Peanut is one of the foods that most often cause a severe allergic reaction.
Who is this useful for
The result says the most when there has been a clear reaction shortly after eating peanut, as an addition to the conversation with the doctor. In people who eat peanut normally and have never had an acute reaction to it, a positive result does not mean you are allergic and can lead to avoiding peanut unnecessarily. With vague symptoms such as abdominal pain, tiredness or eczema without a clear link to a meal, the test adds little.
Downsides and risks
- A positive result without symptoms easily leads to peanut being left out of the diet unnecessarily. That can lead to a shortage of nutrients and, according to Thuisarts.nl, actually increase the chance of an allergy, especially in children.
- A normal result does not rule out symptoms caused by peanut: some people with symptoms have no IgE antibodies that can be found in the blood.
Sources
Always discuss an abnormal result with your GP. If a result is strongly abnormal, we try to reach you as soon as possible. Read your result yourself as well and contact your GP if in doubt. A test does not make a diagnosis. Read more about risks and results