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Managing photopatch test results: How should we interpret these?
Photobiology Unit, Ninewells Hospital, Dundee DD1 9SY, Scotland, UK
When reviewing the photopatch test literature, there is no doubt that a number of problems emerge. Probably the most obvious of these is the difference in methodologies used and published by different groups. It was in recognition of this that a consensus methodology for Europe was produced and published .
Other problems that have significantly bedevilled the literature and in no small way have been responsible for the underuse of photopatch testing, are the presence of false-negative and -positive photopatch test results. When using the consensus methodology in a multicentre photopatch test study group in the UK , photoaugmentation and photoinhibition was encouraged to be recorded as part of the standard photopatch test technique. In addition, crescendo and decrescendo patterns illustrating photoallergy and phototoxicity (irritancy)  are important when deciding the mechanism. Finally, when obtaining a true positive reaction, a decision is required as to the relevance of the readings. One such system that is in routine use within the European Multicentre Study currently underway is COADEX (C = current relevance; O = old or past relevance; A = actively sensitised; D = do not know; and EX = no history of exposure) .
With careful interpretation, the photopatch test technique provides essential management information. Too often we have patients with a suspected photodermatoses who have not had photopatch testing conducting with the consequences of a misdiagnosis. Both contact and photodermatology investigational clinics should make good use of this investigation which currently is underused. Why should this be? To some extent the addition of an extra parameter, i.e., ultraviolet A, has resulted in this investigation falling between two stools. Careful evaluation of the results is essential as part of restoring the confidence in this underemployed technique.
These studies demonstrate the strong phototoxic and photocontact allergic sensitisation potential of CPE in Neuriplege® cream. Its previous availability to consumers within the European Union means many have been sensitised.
© James Ferguson (text) and Radoslaw Spiewak (source code).
This page is part of the website photopatch.eu (contact).
Document created: 30 August 2009, last updated: 31 August 2009.