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Patch Testing With Methylchloroisothiazolinone/Methylisothiazolinone Using a New Diagnostic Mix-A Multicenter Study
Marléne Isaksson1, Klaus E Andersen2, Peter Elsner3
1From the Department of Occupational and Environmental Dermatology, Skåne University Hospital, Lund University, Malmö, Sweden.
Dermatitis : Contact, Atopic, Occupational, Drug
|January 6, 2021
Summary
A new methylchloroisothiazolinone (MCI) and methylisothiazolinone (MI) mixture (0.215%) is more effective for detecting MCI/MI allergy than current patch tests. This improved diagnostic accuracy supports its adoption in allergy testing.
Area of Science:
- Dermatology
- Contact Allergy
- Allergen Testing
Background:
- Methylchloroisothiazolinone (MCI) and methylisothiazolinone (MI) mixture, introduced in the early 1980s, has been used in patch testing globally.
- Current standard patch testing concentrations include 100 ppm (0.01%) worldwide and 200 ppm (0.02%) in Sweden, with the latter also included in the European baseline series since 2014.
Purpose of the Study:
- To compare the diagnostic efficacy of a new aqueous mixture of MCI 0.015% and MI 0.2% against existing baseline patch test preparations.
- To evaluate the performance of MCI/MI 0.02% and MI 0.2% aqueous solutions in patch testing.
Main Methods:
- A multicenter study involving 4,397 patients with dermatitis across 12 International Contact Dermatitis Research Group (ICDRG) departments on three continents.
- Simultaneous patch testing of all patients with three different MCI/MI preparations: the new mixture and the two existing baseline preparations.
Main Results:
- Positive patch test reactions to MCI/MI allergens ranged from 0% to 26.7% across the 12 participating test centers.
- The novel MCI/MI 0.215% aqueous mixture demonstrated significantly higher detection rates for MCI/MI allergy compared to both MCI/MI 0.02% aqueous (P < 0.001) and MI 0.2% aqueous (P < 0.001) alone and in combination.
Conclusions:
- The study findings strongly support the replacement of the current MCI/MI 0.02% aqueous and MI 0.2% aqueous preparations.
- The new MCI/MI 0.215% aqueous mixture is recommended for inclusion in the International Contact Dermatitis Research Group (ICDRG) baseline series due to its superior diagnostic performance.