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Patch testing with p-toluene diamine preparations of different ages
Johannes Geier1, Holger Lessmann, Axel Schnuch
1Information Network of Departments of Dermatology, University of Göttingen, Göttingen, Germany. jgeier@ivdk.org
Contact Dermatitis
|July 22, 2005
Summary
The stability of p-toluene diamine (PTD) in patch testing preparations is a concern, but studies show aged PTD does not compromise diagnostic quality. The true allergen is likely a reaction product, not PTD itself.
Area of Science:
- Dermatology
- Allergology
- Chemical analysis
Background:
- 1% p-toluene diamine (PTD) in petrolatum is used for patch testing.
- PTD concentration declines significantly in petrolatum, potentially due to dye complex formation.
- The impact of these chemical changes on diagnostic accuracy is unknown.
Purpose of the Study:
- To assess if chemical degradation of PTD affects its diagnostic quality in patch testing.
- To evaluate the reliability of aged PTD preparations for contact dermatitis diagnosis.
Main Methods:
- A multicentre study involving 177 patients was conducted by the German Contact Dermatitis Research Group (DKG).
- Simultaneous patch testing was performed using PTD preparations of varying ages (2-20 months).
- Patch test results from different aged batches were statistically compared.
Main Results:
- No statistically significant differences in patient reactions were found between PTD batches of different ages (A, B, and C).
- The agreement of patch test reactions across the three batches was very good.
- Reproducibility was comparable to standard patch test allergens.
Conclusions:
- Chemical reactions and concentration decline in PTD petrolatum preparations do not compromise diagnostic quality.
- The actual allergen in PTD patch tests is likely a reaction product, not PTD itself.
- Aged PTD preparations remain diagnostically reliable for identifying contact dermatitis.