Allergy and intolerance
IgE antilichamen wilg
Antibodies against goat willow pollen; shows whether the immune system is sensitive to willow pollen, not whether it bothers you.
Everything about this testWhat it measures
The goat willow (Salix caprea) is a shrub or small tree that flowers early in spring, usually in March and April, with its well-known catkins. Willows are partly pollinated by insects and therefore release less pollen into the air than, for example, birch or alder. This test measures the amount of IgE antibodies against goat willow pollen in the blood, in kU/l. The body only makes these antibodies after it has previously been in contact with the allergen; this is called sensitization.
- Sensitization to willow pollen: the body has made IgE antibodies against willow pollen
- Support in working out hay fever early in spring, together with the history of the symptoms
High
A value above the cut-off means that you have IgE antibodies against willow pollen: sensitization. That is not the same as an allergy. In people with symptoms such as sneezing, a blocked or runny nose, itchy or watery eyes or shortness of breath in March and April, a positive result fits hay fever from tree pollen. Other trees, such as birch, flower in the same weeks and release more pollen into the air; the result therefore says the most together with the results for other tree pollen. In people without such symptoms, a positive result only means that the antibodies are there; no treatment follows.
Low
A value below the cut-off means that no IgE antibodies against this allergen were found. An IgE-mediated allergy to this allergen is then much less likely, although it is not completely ruled out. Symptoms can also come from another allergen that was not tested, or have a non-allergic cause.
If your result is abnormal
The GP mainly looks at the history: in which months and where the symptoms occur, and whether there are symptoms in the mouth after eating fruit or nuts. With a positive result and matching symptoms, advice follows to reduce contact with pollen, such as keeping windows closed on dry, sunny days, and if needed medication for the nose and eyes. With a lot of symptoms despite medication, an allergist or ENT specialist can discuss immunotherapy, where the result for single allergens helps determine which pollen it targets.
Reliability
A positive IgE result shows sensitization, not allergy: it only says that there are antibodies, not that you get symptoms from them. The Dutch medical specialists' guideline (FMS) on upper airway allergy says this literally and recommends choosing a test for single allergens based on the history of the symptoms; for food allergy, the FMS guideline on food challenge testing calls the history of the symptoms the cornerstone of diagnosis and a food challenge in hospital the gold standard. The result therefore only means something if it fits when, where and after contact with what you get symptoms. A positive result without symptoms is not treated.
Limitations
- Sensitization without symptoms is common; the result can only be interpreted together with the history of the symptoms.
- Related allergens can recognize each other's antibodies (cross-reaction), for example pollen and nuts or fruit; a positive result then does not mean that this particular allergen causes the symptoms.
- The test measures all proteins from the allergen source together; testing for individual proteins (components) can say more in case of doubt.
- Laboratories use different measurement methods and cut-off values; results from different labs cannot be compared one to one.
How common is this
Hay fever is common and often starts at a young age. According to the Longfonds (Dutch lung foundation), trees cause symptoms from January to May; according to Thuisarts.nl, hay fever from trees starts in February or March and symptoms are usually worst between March and the end of May. Sensitization is more common than the allergy itself.
Who is this useful for
Useful with symptoms of the nose, eyes or airways that come back every year early in spring, especially in March and April, outdoors or with willows near the home. The result says the most together with the test for birch pollen and the history of the months in which you have symptoms. In people without such symptoms, the test adds nothing: sensitization without symptoms is not a disease and is not treated.
Sources
- NVKC, allesovertesten.nl: Allergie (RAST)
- FMS Richtlijnendatabase: Allergie van de bovenste luchtwegen, module Aanvullende diagnostiek
- FMS Richtlijnendatabase: Voedselprovocatie, module Plaatsbepaling diagnostiek voedselallergie
- Thuisarts.nl: Ik heb allergie
- Thuisarts.nl: Ik heb hooikoorts
- Longfonds: Hooikoorts
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