Allergy and intolerance
IgE antilichamen kabeljauw
Antibodies against fish protein; shows whether the immune system is sensitive to cod, not whether it gives you symptoms.
Everything about this testWhat it measures
This test measures the amount of IgE antibodies against the proteins in cod 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 indicates from which value the result counts as positive.
- Sensitization to cod: the body has made IgE antibodies against cod
- Support in investigating a suspected allergy to cod, together with the story of the symptoms
- Rarely: a clue in investigating an earlier severe allergic reaction after eating fish
High
A value above the cutoff means that you have IgE antibodies against cod: sensitization. This is not the same as an allergy. According to Stichting Voedselallergie (Dutch food allergy foundation), fish allergy is more common in adults than in children and usually lasts for life. Symptoms that fit it are itching in the mouth and throat, hives, swelling of the lips, vomiting, shortness of breath or, rarely, a severe reaction with a drop in blood pressure. A result for cod does not say whether you also react to other kinds of fish, and nothing about crustaceans and shellfish either: those are different proteins. According to the Dutch Society for Clinical Chemistry (NVKC), the level of the result says nothing about how severe a reaction would be, although a clearly higher value does go with a greater chance that there really is an allergy.
Low
A value below the cutoff means that no IgE antibodies against cod have been found. An IgE-mediated allergy to cod is then a lot less likely. In two studies in the Dutch medical specialists' guideline (FMS), the IgE test for fish found 67 to 94 out of 100 people with a confirmed fish allergy, so occasionally a true allergy is missed. 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 the suspected food and then reintroducing it. If a true allergy is suspected or after a severe reaction, a referral follows to an allergist or pediatrician, where a food challenge test is done if needed; according to the Dutch medical specialists' guideline (FMS), this test is the gold standard.
Reliability
A positive IgE result shows sensitization, not allergy: it only means that there are antibodies, not that cod gives you symptoms. In the Dutch medical specialists' guideline (FMS), the fish IgE test had a specificity of 65 and 88 percent in two studies: some people without a fish allergy still test positive. Because a positive result also occurs in people without an allergy, the result can cause confusion when viewed separately from the symptoms. The result can only be interpreted together with the story of the symptoms and, if in doubt, with a food challenge test in the hospital.
Limitations
- The test only measures cod; other kinds of fish contain partly different proteins and are not measured here.
- Crustaceans and shellfish are different allergens; this result says nothing about them.
- In people with a pollen allergy or with a lot of IgE in the blood, positive results without symptoms are more common.
- Laboratories use different measuring methods; results from different labs cannot always be compared one to one.
How common is this
Fish allergy is fairly rare: in Europe, an estimated 0.1 to 0.2 in 100 people have a fish allergy. Unlike allergy to milk or egg, fish allergy often only starts in adulthood and usually does not go away. Food allergy in general occurs in about 1 to 2 in 100 adults.
Who is this useful for
The result says the most when there has been a clear reaction shortly after eating cod, as an addition to the conversation with the doctor. In people who eat cod normally and have never had an acute reaction to it, a positive result does not mean that you are allergic and can lead to unnecessarily avoiding cod. 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 cod being unnecessarily left out of the diet. This can lead to a shortage of nutrients and, according to Thuisarts.nl, can actually increase the chance of an allergy, especially in children.
- A normal result does not rule out symptoms caused by cod: there are people with symptoms in whom no IgE antibodies 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