Standards for prick skin testing and patch testing
Question:
5/16/2024
I am considering a research project involving allergen (prick) skin testing and patch testing. Before embarking on those projects, I have considered two questions for which I have not been able to find data in the current literature.
1. Wheal, flare, induration, etc. are clinical findings to which allergist assign numerical (e.g., +4. +3, etc.) or descriptive (e.g., mild, moderate) terms based upon our senses of site and touch. Is there a need for our field to develop technique(s) to more objectively and quantitatively read allergy skin tests and patch tests? In addition, if these techniques are more sensitive than our human senses, might that allow us to reduce the reagents required for testing and reduce risk to our patients? Are these goals worth pursuing?
2. Are there any data regarding the impact of skin color on allergy skin tests? Do physicians avoid performing skin tests in some patients due to skin color? Is the accuracy of our current methods of assessing skin reactions impeded by skin color? Is there an unmet medical need to develop better techniques for assessing skin test results especially in patients with skin of color?
I would appreciate your input on whether there is literature which I've missed and/or whether in your opinion these questions deserve our attention. In brief, is there an unmet medical need for improved techniques for assessing skin tests especially in patients with skin of color?
Answer:
The Allergy Diagnostic Testing: An Updated Practice Parameter published in 2008 remains the reference standard for prick skin testing.
https://www.aaaai.org/Aaaai/media/MediaLibrary/PDF%20Documents/Practice%20and%20Parameters/allergydiagnostictesting.pdf
Summary Statement 9. The peak reactivity of prick/puncture tests is 15 to 20 minutes at which time both wheal and erythema diameters (or areas) should be recorded in millimeters and compared with positive and negative controls. (B)
Summary Statement 10. Qualitative scoring (0 to 4 ; positive or negative) is no longer used by many clinicians because of inter-physician variability in this method of scoring and interpretation. (B)
Contact dermatitis: a practice parameter-update 2015 remains the reference standard for patch testing.
Fonacier L, Bernstein DI, Pacheco K, Holness DL, Blessing-Moore J, Khan D, Lang D, Nicklas R, Oppenheimer J, Portnoy J, Randolph C, Schuller D, Spector S, Tilles S, Wallace D; American Academy of Allergy, Asthma & Immunology; American College of Allergy, Asthma & Immunology; Joint Council of Allergy, Asthma & Immunology. Contact dermatitis: a practice parameter-update 2015. J Allergy Clin Immunol Pract. 2015 May-Jun;3(3 Suppl):S1-39.
Summary Statement 19: Read and interpret PT conforming to the scoring system developed by the International Contact Dermatitis Research Group. [Strength of Recommendation: Moderate; D Evidence]
https://link.springer.com/book/10.1007/978-3-642-45395-3
Summary Statement 20: Remove and read PT at approximately 48 hours after application. A second reading should be done between 3 and 7 days after application. [Strength of Recommendation: Moderate; C Evidence]
Patch testing remains challenging to interpret in skin of color given the need to see erythema, particularly for a 1 + positive interpretation, when using the scoring system developed by the International Contact Dermatitis Research Group.
Tamazian S, Oboite M, Treat JR. Patch testing in skin of color: A brief report. Pediatr Dermatol. 2021 Jul;38(4):952-953.
Scott I, Atwater AR, Reeder M. Update on Contact Dermatitis and Patch Testing in Patients With Skin of Color. Cutis. 2021 Jul;108(1):10-12.
Burli A, Vashi NA, Li BS, Maibach HI. Allergic Contact Dermatitis and Patch Testing in Skin of Color Patients. Dermatitis. 2023 Mar-Apr;34(2):85-89.
Eric Macy, MD, MS, FAAAAI