Supplemental patch testing often needed to identify allergens in contact dermatitis

Reuters Health - 09/11/2021 - Supplemental patch testing beyond the standard screening series of allergens is needed for the proper management of contact dermatitis, researchers say.

"Patch testing is an important tool for elucidating potential causes of eczematous dermatitis.... but it is only as good as the number of allergens/substances tested," Dr. Erin Warshaw of the University of Minnesota in Minneapolis told Reuters Health by email. "A screening series of 65-70 allergens missed at least one relevant allergen in about one-fifth of patients patch tested in this study."

"This has important implications for insurance coverage for patches which, in some cases, limits the number of patches covered," she said. "Correct identification and subsequent avoidance of allergens can be curative and life-changing for patients. In addition, comprehensive patch testing saves future healthcare dollars by obviating ongoing treatment for dermatitis, including costs of clinic visits and prescription medications (e.g., expensive biologic medications)."

As reported in JAMA Dermatology, Dr. Warshaw and colleagues did a 17-year, retrospective cross-sectional analysis of 43,417 patients from multiple centers who went through with the North American Contact Dermatitis Group (NACDG) screening series (65-70 allergens) and supplemental allergens as clinically indicated.

Close to 22% of those tested (mean age, 47.2; 69.5% women) had relevant reactions to one or more supplemental allergens or substances.

Compared with patients who had negative results, those with positive findings on supplemental allergen testing were significantly less likely to be male (odds ratio, 0.90) and/or have atopic dermatitis (OR, 0.89).

The most common primary sites of dermatitis for those with supplement-positive findings were the face (30.1%]), hands (21.4%), and scattered/generalized distribution (17.3%).

Frequent sources of supplemental allergens were personal care products (51.4%); clothing/wearing apparel (18.1%); and occupational exposures (16.9%), and about a quarter (25.1%) of identified occupations were precision production, craft, or repair workers.

Notably, 25.7% of those with positive supplemental allergen findings had no relevant reactions to NACDG screening allergens.

The authors conclude, "Screening series include common, important allergens, but these findings suggest that the addition of specialty allergens and personal or work products is critical for the successful diagnosis and management of allergic contact dermatitis."

Dr. Warshaw noted, "Supplemental allergens vary by unique patient exposures, including occupation and regional factors. For example, important supplemental allergens in a surgeon with hand dermatitis would include supplemental allergens in surgical gloves and antiseptic cleansers; this differs from the supplemental allergens chosen for a retired individual with anogenital dermatitis, which would include ingredients used in medications."

"Cultural exposures may vary," she added. "Dermatologists with knowledge of local practices are in the best position to determine which allergens are appropriate for each patient."

Dr. Frank Morocco, an OhioHealth dermatologist in Marion, commented in an email to Reuters Health, "This paper highlights the limitations of screening alone for contact allergens. If a screening series is negative for contact dermatitis, it certainly does not conclusively rule out a contact etiology."

"Supplemental allergen testing should be considered if there is still a high clinical suspicion," he said. "A thorough history (is) needed in order to choose the appropriate supplement allergen panel."

"One concern (is) implementing this in day-to-day practice," he noted. "Sometimes it is difficult to obtain and test for supplemental allergens. One of the limitations (mentioned in) the paper was that the study sample was drawn from patients who were referred for patch testing; as such, they are representative of neither the general population nor the general dermatology population."

SOURCE: https://bit.ly/3ocIUAe JAMA Dermatology, online November 3, 2021.

By Marilynn Larkin



Posted on 9 November 202116 November 2021