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The importance of context information in the diagnostic rating of digital images of patch test reactions

Authors

  • W. Uter,

    1. Department of Medical Informatics, Biometry and Epidemiology, University of Erlangen-Nürnberg, Waldstr. 6, D-91054 Erlangen, Germany
      *Department of Dermatology, University of Witten/Herdecke and Klinikum Dortmund gGmbH, Dortmund, Germany
      †Department of Dermatology, University Hospital of Mainz, Mainz, Germany
      ‡Information Network of Departments of Dermatology at the University of Göttingen, Göttingen, Germany
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  • P.J. Frosch,

    1. Department of Medical Informatics, Biometry and Epidemiology, University of Erlangen-Nürnberg, Waldstr. 6, D-91054 Erlangen, Germany
      *Department of Dermatology, University of Witten/Herdecke and Klinikum Dortmund gGmbH, Dortmund, Germany
      †Department of Dermatology, University Hospital of Mainz, Mainz, Germany
      ‡Information Network of Departments of Dermatology at the University of Göttingen, Göttingen, Germany
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  • D. Becker,

    1. Department of Medical Informatics, Biometry and Epidemiology, University of Erlangen-Nürnberg, Waldstr. 6, D-91054 Erlangen, Germany
      *Department of Dermatology, University of Witten/Herdecke and Klinikum Dortmund gGmbH, Dortmund, Germany
      †Department of Dermatology, University Hospital of Mainz, Mainz, Germany
      ‡Information Network of Departments of Dermatology at the University of Göttingen, Göttingen, Germany
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  • A. Schnuch,

    1. Department of Medical Informatics, Biometry and Epidemiology, University of Erlangen-Nürnberg, Waldstr. 6, D-91054 Erlangen, Germany
      *Department of Dermatology, University of Witten/Herdecke and Klinikum Dortmund gGmbH, Dortmund, Germany
      †Department of Dermatology, University Hospital of Mainz, Mainz, Germany
      ‡Information Network of Departments of Dermatology at the University of Göttingen, Göttingen, Germany
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  • A. Pfahlberg,

    1. Department of Medical Informatics, Biometry and Epidemiology, University of Erlangen-Nürnberg, Waldstr. 6, D-91054 Erlangen, Germany
      *Department of Dermatology, University of Witten/Herdecke and Klinikum Dortmund gGmbH, Dortmund, Germany
      †Department of Dermatology, University Hospital of Mainz, Mainz, Germany
      ‡Information Network of Departments of Dermatology at the University of Göttingen, Göttingen, Germany
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  • O. Gefeller

    1. Department of Medical Informatics, Biometry and Epidemiology, University of Erlangen-Nürnberg, Waldstr. 6, D-91054 Erlangen, Germany
      *Department of Dermatology, University of Witten/Herdecke and Klinikum Dortmund gGmbH, Dortmund, Germany
      †Department of Dermatology, University Hospital of Mainz, Mainz, Germany
      ‡Information Network of Departments of Dermatology at the University of Göttingen, Göttingen, Germany
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  • Conflicts of interest None declared.

Wolfgang Uter.
E-mail: wolfgang.uter@imbe.med.uni-erlangen.de

Summary

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.

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