PracticeUpdate: Dermatology - Winter 2018

EDITOR’S PICKS 8

The Medical Necessity of Comprehensive Patch Testing Dermatitis Take-home message • Allergen identification is crucial in the management of allergic contact dermatitis (ACD). The commercially available T.R.U.E Test screening panel (36 allergens) is reported to have a detection rate of, at most, 66.0% of the clinically relevant reactions identified by the North American Contact Dermatitis Group (NACDG). Notably, up to 50% of allergens causing occupational dermatitis aremissed. Studies show that 21% to 34% of ACD diagnoses would be missed by the NACDG screening series without the use of supplemental allergens. Comprehensive testing with supplemental allergens beyond a screening series may increase the diagnostic yield and the likelihood of achieving a cure for ACD. • The authors emphasize the need to integrate the patient's medical history, exami- nation findings, and environmental exposure history to implement comprehensive and customized allergen testing in the management of ACD. InYoung Kim MD, PhD

COMMENT By Salma F. de la Feld MD, FAAD C ontact dermatitis has a significant impact on patients’ quality of life and, as the fifth most prevalent skin disease in the United States, it has a high burden of medical cost at over $1 billion. This article highlights the impor- tance of utilizing comprehensive patch testing to effectively diagnose and cure patients of allergic contact dermatitis. Although “limited” patch testing with 36 allergens can seem easier, it misses up to one-third of the diagnoses found on comprehensive patch testing and misses up to 50% of the causes of occu- pational dermatitis. The time involved with this labor-intensive, 1-week pro- cedure can be a barrier to utilization. However, in the long-run, proper accu- rate diagnosis and counseling with patch testing can avert subsequent office visits and additional unnecessary treatment (decreasing the economic impact of this disease) as well as ulti- mately improving patients’ quality of life. " Although “limited” patch testing with 36 allergens can seem easier, it misses up to one-third of the diagnoses found on comprehensive patch testing and misses up to 50% of the causes of occupational dermatitis. " Comprehensive patch testing is an underuti- lized and helpful tool that should be considered in the evaluation and treatment of allergic contact dermatitis. Patients will often come in saying that they already had “allergy testing” and not realize that they actually had prick or intradermal testing instead, which evaluates for different dis- eases (such as immediate, IgE-mediated type I hypersensitivities). Patch testing eval- uates for delayed-type hypersensitivity and allergic contact dermatitis, and it is important to make this distinction when approaching patients.

Abstract Allergic contact dermatitis is associated with significant disease and economic burden in the United States. To properly manage allergic contact dermatitis, it is important to accurately identify the substance(s) implicated in the der- matitis to prevent disease recurrence. The commercially available T.R.U.E Test (36 aller- gens) screening panel has been reported to have a conservative hypothetical allergen detec- tion rate of 66.0%, at most. Importantly, these calculations are based on the 78% of patients who had clinically relevant reactions to allergens present on the North American Contact Der- matitis Group screening series (70 allergens), without the use of supplemental allergens.

Testing with supplemental allergens beyond a screening series can more fully evaluate an individual's environmental and occupational exposure, which may significantly increase diag- nostic accuracy. Comprehensive patch testing with additional allergens in sunscreens, cosmet- ics, and fragrances, for example, may increase the diagnostic yield as well as the likelihood of achieving a cure if the dermatitis is chronic and recalcitrant. The Medical Necessity of Comprehensive Patch Testing. Dermatitis 2018 Apr 02;29(3)107- 111, TH Zhu, R Suresh, E Warshaw, et al. www.practiceupdate.com/c/68157

Dr. de la Feld is an Assistant Professor at Emory University Department of Dermatology in Atlanta, Georgia, where she is also Co-Director of the Patch Testing Clinic and Director of the Sub-I medical student rotation.

PRACTICEUPDATE DERMATOLOGY