New positive patch test reactions on day 7—The additional value of the day 7 patch test reading

Abstract

Background Not performing a day (D) 7 patch test reading might result in positive patch test reactions being missed. Objectives To investigate the added value of the D7 patch test reading for individual allergens, and to identify patient characteristics and allergen groups associated with new positive D7 reactions. Methods Data from patients patch tested between 2008 and 2018 with the extended European baseline series were analysed. Patch test readings were performed on D3 and D7. Positive reactions were categorized into positive on D3 or new positive on D7. Results A total of 3292 patients were consecutively patch tested with at least 43 allergens of the TRUE Test panels 1 and 2 supplemented with investigator‐loaded allergens. In total, 447 (13.6%) patients showed new positive D7 reactions. In univariable regression analysis, age between 18 and 30 years showed a negative association with new positive D7 reactions. Significantly more D7 positive reactions were seen for topicals (odds ratio [OR] 2.60, 95% confidence interval [CI]: 1.92‐3.51) and corticosteroids (OR 1.87, 95%CI: 1.09‐3.21). No associations were found between sex, atopic dermatitis and occupational dermatitis and a new positive D7 reaction. Conclusion A D7 reading to identify new positive patch test reactions is of added value, especially for topicals and corticosteroids.

Value of photo assessment in late patch test readings—A multicenter study from six European patch test clinics

“…The value of a clinical reading performed on D7 has been discussed by several research groups. Although some studies strongly recommend a D7 reading for all allergen series, others only find it important for allergens such as metals, topical antibiotics, and acrylates 4,5,7‐9,26,27 . In our study, 6.3% of all positive reactions were found on D7 only, comprising nickel, formaldehyde, cobalt, gold, and budesonide as the most frequent causative allergens in accordance with previous findings 4,5,7‐9,26,27 .…”

“…Van Amerongen et al found 13.6% new positive reactions on D7 in patients tested with allergens from the European Baseline Series, TRUE Test, and additional unspecified allergens chosen by the investigator through a 10‐year period. Cantwell et al found approximately 30% new positive reactions on D7 in 411 patients tested with multiple series, whereas Madsen et al reported 4.4% new positive reactions on D7 in patients with hand eczema who were tested with TRUE Test only 4,8,27 . Because we included the European Baseline Series and TRUE Test only, the prevalence of late reactions in our study may have been even higher if additional series had been included in the assessment.…”

“…According to recent guidelines for diagnostic patch testing by the European Society of Contact Dermatitis, readings should ideally be performed three times: day (D)2, D3 or D4, and around D7, 3 thus requiring the attendance by the patient at four different visits. Several studies have previously confirmed the importance of the D7 reading to detect late reactions, which would otherwise be missed, in particular for diagnosing contact allergy to allergens such as neomycin and topical corticosteroids, but reactions to other allergens may also be discovered at D7 only 4‐10 . However, because contact dermatitis often affects younger people who are active in the labor market, and sometimes may even be caused by occupational exposure, absence from work due to patch testing may be inconvenient or stressful for the patient 11‐13 .…”

Patch testing and diagnosis when suspecting allergic contact dermatitis from medical devices

“…7 Furthermore, by adding a patch test reading on D7 to the D3/D4 reading, an additional 3%-34% of sensitized cases can be identified. 8 When it comes to (meth)acrylates, late reactions are well known, with about 10% of positive reactions occurring first on reading D7 or later, [9][10][11] without being cases of active sensitization. 10 Thus, a patch test reading on D7 is mandatory to increase diagnostic accuracy.…”

Contact Allergy to Nickel: Still #1 After All These Years

“…A 2019 analysis of the prevalence of new patch test reactions on day 7 showed that 17% of 607 patients were negative on day 3 but were positive on day 7, further emphasizing the importance of a properly timed delayed reading. 12…”