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Thoughts on the interpretation of positive photopatch test reactions
1Department of Occupational and Environmental Dermatology, Lund University, Skåne University Hospital, Malmö, Sweden.
Background:
Positive photopatch test reactions are classified according to the International Contact Dermatitis Group. The various reaction patterns are interpreted to represent patterns such as contact allergy, photocontact allergy, photoaugmentation, and photoinhibition.
Objective:
To investigate whether there are any weaknesses in the interpretation of reaction patterns.
Materials & Methods:
A dermatitis patient with photoallergic contact dermatitis due to ketoprofen was photopatch tested with serial dilutions of ketoprofen in ethanol. The reaction patterns for the various concentrations were used as a basis for discussion on weaknesses regarding the present interpretations of positive photopatch test reactions.
Results:
The reaction patterns to the ketoprofen photopatch at various concentrations were interpreted as (i) contact allergy, (ii) contact allergy with photoaugmentation, (iii) contact allergy and photocontact allergy, and (iv) photocontact allergy.
Conclusion:
The present interpretation of positive photopatch test reactions is unreliable and therefore insufficient regarding appropriate advice for patients.
