(( the meeting
(( the course
(( key dates
(( basic facts
(( contact us
Photopatch tests: consensus methodology, present standard procedures
Derk P. Bruynzeel
Dermato-allergology & Occupational dermatology, VU University Medical Centre, Amsterdam, The Netherlands
The European Taskforce for Photopatch Testing, an initiative of the European Society for PhotoDermatology and the European Society of Contact Dermatitis, published in 2004 a consensus methodology on photopatch testing. This is an important step in standardization. The test procedure, for general purposes, will be explained.
The light source, patch test materials, allergens, application period and the reading method are standardized. As light source is chosen a broad-spectrum fluorescent PUVA lamp. The allergens, placed preferable in Finn chambers, are applied in duplicate to the upper back and covered with opaque material. After 24 or 48 hours the materials are removed and one site is irradiated with 5 J/cm2, the non-irradiate site is again covered with opaque material after the first reading. The standard photopatch test series consists in organic sunscreens and NSAIDs. Readings are performed direct after removal of the allergens and again after the irradiation. The next readings are preferably 48 hours and 72 or 96 hours post-irradiation.
The reading of patch tests is always a two-step procedure. First step: scoring of the reaction without any interpretation of the nature of the reaction. Second step: interpretation of the nature of the reaction. The scoring of the reactions is according the standard ICDRG scoring system for patch tests: ranging from ?+ through +++. The interpretation of the photopatch test may be difficult. Regarded as a positive photopatch test is a reaction (> ?+) at the irradiated site and negative at the non-irradiated control site. Positive reactions at both sites are not regarded as positive photopatch tests but as positive contact reactions, which can be aggravated at the irradiated site by the UV-light. The relevance of a positive reaction depends on the possible exposition to the allergen in combination with UV, dermatitis in the correct topographically area and there should be a time correlation.
© Derk P. Bruynzeel (text) and Radoslaw Spiewak (source code).
This page is part of the website photopatch.eu (contact).
Document created: 12 August 2009, last updated: 31 August 2009.