Siegel-PD; Fowler-JF; Law-BF; Warshaw-EM; Taylor-JS
Toxicologist 2013 Mar; 132(1):306-307
Epicutaneous patch tests (EPT) are commonly used to identify chemical agents of allergic contact dermatitis in dermatology patients. Test validity and assessment of allergic reaction severity are highly dependent on the use of reliable chemical allergen test reagents. The purpose of the present study was to measure the actual concentration of nickel sulfate (NiSO4), methyl methacrylate (MM), formaldehyde (FA) and glutaraldehyde (GA) compared to the labeled concentrations of commercial reagents found in dermatology clinics where patch testing is routinely performed. The commercial reagents, NiSO4, MM and GA are supplied either dissolved or suspended in petrolatum (usually in syringe, multiuse containers) while FA is diluted in water. Participating clinics submitted in-date and out-dated reagents to the laboratory for analyses. Both NiSO4 and FA levels were at or above the labeled concentration. NiSO4 particulate was uniformly distributed throughout the petrolatum. In contrast, MM was low and variable in commercial allergen reagents. "In-use" MM reagent syringes were all = / < 56% of the 2% label concentration with no observable relationship to expiration date. One MM syringe purchased directly from the manufactured was 70% of the labeled concentration. Lower MM levels in syringes were consistently measured at the tip vs. plunger end of the syringe suggesting loss due to MMís volatility. GA patch test reagents concentrations ranged from 27 to 45% of the labeled (1% in petrolatum) amount, independent of expiration date. No GA concentration pattern between tip and plunger was observed. These data suggest that false negative EPT results may be due to instability of volatile or self-polymerizing chemical allergens in the test reagents.
Toxicology; Patch-tests; Dermatology; Dermatitis; Allergic-dermatitis; Allergic-reactions; Allergens; Reaction-rates; Reagents; Nickel-compounds; Sulfates; Methyl-compounds; Methacrylates; Formaldehydes; Aldehydes; Testing-equipment; Medical-equipment; Diagnostic-tests; Clinical-tests; Skin; Skin-tests; Skin-sensitivity; Volatiles; Contact-allergies; Contact-dermatitis
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The Toxicologist. Society of Toxicology 52nd Annual Meeting and ToxExpo, San Antonio, Texas, March 10-14, 2013