Phadiatop

  1. Why is it better to use Phadiatop as a “screening test” instead of Total IgE when atopic allergy is suspected?

    Only around 50 % of patients with respiratory allergies have increased total IgE (>100 kU/l), which in fact means that 50 % with normal total IgE will not be identified by total IgE testing.

    The total IgE level is the sum of all IgE in the blood, which can be increased due to other reasons than allergy. Instead Phadiatop is recommended with its superior performance, which only measures allergen-specific IgE antibodies to common allergens and not the total amount where irrelevant IgE could be included.

  2. How reliable is Phadiatop as a test in order to confirm or exclude atopic allergy?

    The sensitivity (to confirm allergy) as well as the specificity (to exclude allergy) of Phadiatop have in many studies been documented to be at least 90 %, i.e. more than 9 out of 10 correctly diagnosed individuals. Despite its excellence Phadiatop is not 100 %, but far better than could be achieved by diagnosing allergy without using any test, where the efficiency has been shown to rarely exceed 50 %.

  3. How does Phadiatop work?

    This is a single test that measures IgE antibodies (sensitization) to common inhalant allergens such as grass, tree & weed pollen, animal, mite and mold provoked after normal environmental exposure.

    Typical symptoms are asthma, rhinitis and eczema, but as always a positive test result doesn’t necessarily mean that the patients must have allergic symptoms at the time.

  4. When is Phadiatop indicated?

    1) To help confirm or exclude atopic allergy, i.e. IgE antibodies after normal exposure to common environmental allergens, when no clear indication about what to test exists.

    2) Cases sensitized by food or by keeping more or less exotic pets like birds, guinea pigs etc. are most often also co-sensitized to common inhalants and will thus be positive with Phadiatop.

  5. When is Phadiatop not indicated?

    1) If strong suspicion of certain specific provoking allergens, test directly for allergen-specific IgE antibodies without prior atopy testing with Phadiatop to achieve highest sensitivity.

    2) When non-atopic allergy is suspected, i.e. IgE antibodies primarily to allergens such as drugs, venoms and occupational allergens, which may provoke an IgE response only after excessive allergen exposure.

  6. Will Phadiatop cover all age groups?

    1) Phadiatop is for older children and adults, containing only common inhalant allergens.

    2) Phadiatop Infant is for children less than 5 years covering common food and inhalant allergens.

  7. How can Phadiatop cover all important inhalant allergens worldwide?

    Phadiatop consists of a well-balanced mixture of common inhalant allergens relevant for the age and region of the patients. The test is utilizing patient cross-sensitizations (IgE antibodies to similar structures in different allergens) as well as co-sensitizations (simultaneous sensitizations to different allergens) to cover most of the common allergens, which are the basis behind the atopy concept.

  8. Which allergens to follow-up a positive Phadiatop when the exact content is unknown?

    The main purpose of using Phadiatop is to confirm or exclude atopic allergy in patients presenting with unclear allergy-like symptom. Follow-up testing of positive Phadiatop to identify the causative allergens should not be according to the ingredient allergens but to the individual clinical history of the patient, and the allergens the patient is actually exposed to.

  9. How could I trust that the important allergens in my country are included?

    The common allergens are in principle the same worldwide such as animal, mite and mold. Others such as different pollen cross-react to a high degree within each group, so even if not exactly the specific pollen for your country is included, the ones selected will work fine.

    Before introduction, Phadiatop is checked locally in each market to ensure its efficiency to identify atopic allergy.

  10. What are the major benefits of using Phadiatop?

    Phadiatop helps when you are uncertain if your patient have atopic allergy or not and hence cost-effectively reduces unnecessary allergy testing. It also identifies those patients who are the correct ones to get continued testing. A positive Phadiatop shall lead to at least one, but often several positive allergen-specific IgE tests.

  11. Is it possible to have a positive Phadiatop, without any positive follow-up Specific IgE tests?

    No, it should in fact not be possible if single positive results are reported according to Direction For Use, i.e. from 0.1 kUA /l; either you haven’t selected the right allergens to test (a positive Phadiatop is due to IgE antibodies to one or several of the common inhalant allergens in the patient’s enviroment) or it might be caused by technical problems or sample mix-up in the laboratory.

  12. Summarize possible reasons behind a negative Phadiatop despite a positive single allergen?

    1) Phadiatop has a sensitivity of >90 %, which is very good, but somewhat lower sometimes than a single allergen.

    2) The patient may be monosensitized to food or other allergens not covered by Phadiatop.

    3) Due to non-atopic allergy with sensitization only to allergens such as venoms, drugs or occupational allergens.

  13. How come that a patient with a negative Phadiatop could have a positive e.g. Nut mix?

    Phadiatop only contains inhalant allergens and does not contain pure food allergens. If the patient has an isolated nut allergy and is sensitized only to allergens contained in the food/nut, e.g. storage proteins, the patient will be negative on Phadiatop. The majority of food allergic patients are co-sensitized to inhalant allergens and will thus be identified with Phadiatop as atopic anyway, but some patients do have a “pure” food allergen sensitization and will only be identified when testing with the appropriate food allergens. If true nut allergy is suspected, the patient could get very severe reactions such as anaphylaxis and the specific nut should always be the test of choice.

  14. How come that many of my Phadiatop tests are negative?

    All allergy-like symptoms are not due to IgE mediated allergy, e.g. in eczema 1– 2 out of 3, in rhinitis 3 out of 10 children, and in wheezing 1 out of 3 are not allergic. It is shown that physicians rather make the diagnosis of allergy than exclude it (i.e. overdiagnosing) when no allergy tests are used. Phadiatop increases certainty in allergy diagnosis, but also helps to rule out allergy.

  15. What is the relation between kUA/l and PAU/l?

    There is a strong correlation between PAU/l from Phadiatop and the sum of kUA/l from single allergen determinations of the included allergens, but in general somewhat lower levels could be expected with Phadiatop. To simplify the interpretation of Phadiatop many laboratories use the same unit (kUA/l) for Phadiatop as for Specific IgE, however not 100 % correct but will not lead to any clinical implications and could thus be accepted.

  16. How can I utilize the quantitative level of Phadiatop (0.35 – 100 PAU/l)?

    Phadiatop is reported in a quantitative manner (atopy grading) and regarded positive if ≥0.35 PAU/l. The result reflects the degree of sensitization (adds up the sum of IgE antibodies) to common environmental allergens. Patients having Phadiatop results of e.g. 1 PAU/l and 75 PAU/l respectively, are most probably having totally different clinical presentation; the higher the level the higher probability of clinical symptoms. The Phadiatop level could also guide if you should keep looking (sum of Specific IgE at much lower level) or stop looking (sum of Specific IgE at similar level) for additional IgE provoking allergens.

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.