llergy Testing: When to test, when not to and what to do with the results

Transcription

1 llergy Testing: When to test, when not to and what to do with the results Kelly Maples, MD, FAAAAI, FACAAI Assistant Professor of Pediatrics and Internal Medicine CHKD/EVMS

2 Sensitization Allergy

3 The results of allergy testing are only as good as the indication for testing.

4 2 year old boy moderate atopic dermatitis Hives and vomiting after eating peanut butter Tolerates egg, milk, wheat, soy, fish and almond milk. Has not tried shellfish. Food panel: Egg 4.24kUa/L, milk 5.09, fish 0.41, wheat 0.58, peanut 67.2, soy 1.82, tree nuts positive Shrimp, corn, tomato, orange, apple, chicken negative

5 Valid types of testing Allergy skin prick testing Intradermal testing Specific IgE testing/immunocap Atopy patch testing

6 Invalid types of testing IgG to foods Intradermal testing to foods Cytotoxic assays Applied kinesiology Hair analysis Provocation neutralization Alcat sensitivity test

7 Types of Testing Although correlation of higher levels of specific IgE to some allergens is equivalent to skin testing, skin prick tests generally have better overall predictability and are the preferred initial diagnostic test for IgE mediated allergy.

8 llergy Skin Prick Testing Skin prick testing is safe. Results should be reported in mm. Routine use of a large number of skin tests or routine annual testing is not justified. Immunotherapy should not be based on positive testing alone.

9 Intradermal Testing Intradermal tests are used for venom, penicillin and delayed anaphylaxis to meats. Should NEVER be done to food allergens in any other circumstance. May be used if prick testing is negative and there is a strong likely hood of clinical allergy to specific environmental allergens.

10 Patch Testing Atopy patch testing determines presence of type IV hypersensitivity Contact dermatitis Atopic dermatitis Prior to metal implant surgery Occasionally in eosinophilic esophagitis No evidence for FPIES

11 Respiratory Allergy Environmental Allergens Environmental control Anticipation of flares Immunotherapy Mepolizumab Food allergy testing is NOT indicated.

12 Chronic Urticaria and Angioedema No allergy testing indicated. No additional testing needed in absence of symptoms.

13 Venom Allergy Indicated for systemic allergic reactions in any age patient and in patients with diffuse urticaria if over 16 at time of reaction. NOT indicated for those with family history, large local reactions or diffuse urticaria in patients under 16.

14 Atopic Dermatits Environmental testing for environmenta control or immunotherapy Consider patch testing in certain patients Food allergy testing ONLY if not responding to skin care regimen with adequate use of topical steroids

15 Atopic Dermatits If positive testing perform a 2 week elimination diet. If no improvement return food to diet. If improvement seen, perform oral food challenge.

16 Atopic Dermatits High false positive rate of skin prick and specific IgE testing. Role of barrier dysfunction and barrier care.

17 Food Allergy Testing should be focused only on foods suspected of provoking a previous reaction. Reasonable to test in families with strong family history. Do not perform an indiscriminate panel of IgE to foods. Specific IgE testing alone is NOT diagnostic of food allergy: Oral

18 Food Allergy

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23 Interpreting Immunocap results Class system devised for environmenta allergy, not foods Each major food allergen has a different clinically significant IgE threshold.

24 Food Allergy Do not use specific IgE based testing to indiscriminately screen for food allergy Great negative predictive value Specificity as low as 40%

25 Food Allergy If clinical history is not consistent with a systemic allergic reaction, perform an oral challenge. Evaluate children with food allergies at regular intervals 1-2 years Adults

26 Food Allergy Children with egg allergy do NOT need to be allergy tested to the influenza vaccine. Limited role of skin prick testing in eosinophilic esophagitis.

27 The results of allergy testing are only as good as the indication for testing.

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32 References Allergy Diagnostic Testing: An Updated Practice Parameter. Annals of Allergy, Asthma, & Immunology, March 2008; Vol 100, No 3, Supp 3 Clinical Management of Atopic Dermatitis: Practical Highlights and Updates from the Atopic Dermatitis Practice Parameter Journal of Allergy and Clinical Immunology In Practice, July 2014 Food Allergy: A Practice Parameter Update Journal of Allergy and Clinical Immunology, 2014; Vol 134, No 5.