Conflicts of interest None declared.
The importance of context information in the diagnostic rating of digital images of patch test reactions
Article first published online: 29 APR 2009
© 2009 The Authors. Journal Compilation © 2009 British Association of Dermatologists
British Journal of Dermatology
Volume 161, Issue 3, pages 554–559, September 2009
How to Cite
Uter, W., Frosch, P.J., Becker, D., Schnuch, A., Pfahlberg, A. and Gefeller, O. (2009), The importance of context information in the diagnostic rating of digital images of patch test reactions. British Journal of Dermatology, 161: 554–559. doi: 10.1111/j.1365-2133.2009.09167.x
- Issue published online: 20 AUG 2009
- Article first published online: 29 APR 2009
- Accepted for publication 19 January 2009
- contact allergy;
- continuing medical education;
- digital image;
- patch testing;
Background Patch test (PT) guidelines recommend classifying PT reactions based on morphological criteria only, i.e. irrespective of context information such as substance, concentration and vehicle.
Objectives To analyse reclassification of PT reactions after revelation of context information subsequent to an initial blinded reading.
Methods One hundred and twenty-two participants (experienced dermatologists and researchers) rated 20 digital images of different PT reactions twice, first blinded, then unblinded regarding substance, concentration and vehicle. Agreement between both ratings was quantified with Cohen’s kappa, and systematic differences statistically examined with tests for marginal homogeneity.
Results Mostly, ratings remained stable, e.g. in > 90% of cases of images showing typical strong or extreme positive PT reactions. Reclassification was comparatively often observed in images depicting irritant reactions. Conversely, 16 of 122 participants re-rated doubtful reactions to thiuram mix and dichromate, respectively, as ‘allergic’ (weak or strong positive) after knowing the substance.
Conclusions The considerable proportion of participants who choose an ‘allergic’ rating, despite a morphological presentation definitely not justifying this, points to a conceptual problem of the PT reading scale: the mixing up of morphological classification and interpretation. We therefore suggest amending the scale. Moreover, standardization of PT reading can be improved by continual PT training sessions.