Allergy Testing: Common Questions and Answers

 

An estimated 10% to 30% of the global population has an allergic disease. Clinical presentations of allergic diseases, respiratory infections, and autoimmune conditions have similar features. Allergy and immunologic testing can help clarify the diagnosis and guide treatment. Immediate immunoglobulin E (IgE) and delayed T cell–mediated reactions are the main types of allergic responses. The allergens suspected in an immediate IgE-mediated response are identified through serum IgE-specific antibody or skin testing. For patients with an inhalant allergy, skin or IgE-specific antibody testing is preferred. In patients with food allergies, eliminating the suspected allergenic food from the diet is the initial treatment. If this is ineffective, IgE-specific antibody or skin testing can exclude allergens. An oral food challenge should be performed to confirm the diagnosis. Patients with an anaphylactic reaction to an insect sting should undergo IgE-specific antibody or skin testing. Skin testing for penicillin has a high negative predictive value and can help when penicillin administration is indicated and there are limited alternatives. Testing for other drug allergies has less well-determined sensitivity and specificity, but can guide the diagnosis. Patch testing can help identify the allergen responsible for contact dermatitis.

An estimated 10% to 30% of the global population has an allergic disease.1 The most common reasons that family physicians request a consultation for allergy testing are recurrent or persistent respiratory symptoms, skin rashes, repeated infections, and adverse reactions to foods, medications, and insect stings.2 Family physicians should consider referring patients to an allergist when there is an inadequate response to treatment or when a more accurate diagnosis would help with management.

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SORT: KEY RECOMMENDATIONS FOR PRACTICE

Clinical recommendationEvidence ratingReferences

Contact dermatitis is tested with a patch test.

C

13

Patients with suspected food allergy should be asked about exposure to cow's milk, hen's eggs, soy, fish, shellfish, tree nuts, wheat, and peanuts, because these are responsible for most food allergies.

C

12

To exclude mast cell activation syndrome, measurement of tryptase levels is recommended in patients with anaphylaxis to insect stings.

C

24

Immunotherapy for insect stings is recommended for patients at risk of severe reactions to future stings.

B

23, 24, 27

Negative skin test results for penicillin allergy have a negative predictive value of 95% to 98% for anaphylaxis. It is safe to prescribe penicillin when results are negative.

B

2831


A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evidence; C = consensus, disease-oriented evidence, usual practice, expert opinion, or case series. For information about the SORT evidence rating system, go to https://www.aafp.org/afpsort.

SORT: KEY RECOMMENDATIONS FOR PRACTICE

Clinical recommendationEvidence ratingReferences

Contact dermatitis is tested with a patch test.

C

13

Patients with suspected food allergy should be asked about exposure to cow's milk, hen's eggs, soy, fish, shellfish, tree nuts, wheat, and peanuts, because these are responsible for most food allergies.

C

12

To exclude mast cell activation syndrome, measurement of tryptase levels is recommended in patients with anaphylaxis to insect stings.

C

24

Immunotherapy for insect stings is recommended for patients at risk of severe reactions to future stings.

B

23, 24, 27

Negative skin test results for penicillin allergy have a negative predictive value of 95% to 98% for anaphylaxis. It is safe to prescribe penicillin when results are negative.

B

2831


A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evidence; C = consensus, disease-oriented evidence, usual practice, expert opinion, or case series. For information about the SORT evidence rating system, go to https://www.aafp.org/afpsort.

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BEST PRACTICES IN ALLERGY/IMMUNOLOGY

Recommendations from the Choosing Wisely Campaign

RecommendationSponsoring organization

Do not overuse non–beta-lactam antibiotics in patients with a history of penicillin allergy without an appropriate evaluation.

American Academy of Allergy, Asthma and Immunology

Do not perform food IgE testing without a history consistent with potential IgE-mediated food allergy.

American Academy of Allergy, Asthma and Immunology

Do not perform screening panels for food allergies without previous consideration of medical history.

American Academy of Pediatrics


IgE = immunoglobulin E.

Source: For more information on the Choosing Wisely Campaign, see https://www.choosingwisely.org. For supporting citations and to search Choosing Wisely recommendations relevant to primary

The Authors

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KU-LANG CHANG, MD, is a clinical associate professor of community health and family medicine at the University of Florida College of Medicine, Gainesville....

JUAN CARLOS GUARDERAS, MD, is an associate professor at the University of Florida College of Medicine.

Address correspondence to Ku-Lang Chang, MD, University of Florida College of Medicine, 200 SW 62nd Blvd., Ste. D, Gainesville, FL 32607 (e-mail: changk@shands.ufl.edu). Reprints are not available from the authors.

Author disclosure: No relevant financial affiliations.

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