Ann Dermatol.  2015 Oct;27(5):557-562. 10.5021/ad.2015.27.5.557.

Reduction of Inter-Rater and Intra-Rater Variability in Psoriasis Area and Severity Index Assessment by Photographic Training

• Youn SW
• Choi CW
• Kim BR
• Chae JB

• KMID: 2171456
• DOI: http://doi.org/10.5021/ad.2015.27.5.557

Abstract

BACKGROUND
Severity grading is important for the assessment of psoriasis treatment efficacy. This is most commonly achieved by using the psoriasis area and severity index (PASI), a subjective tool with inherent inter-rater and intra-rater variability. PASI-naive dermatologists require training to properly conduct a PASI assessment.
OBJECTIVE
In the present study, we aimed to investigate whether photographic training improves inter-rater and intra-rater variabilities. We also determined which PASI component has the greatest impact on variability.
METHODS
Twenty-one dermatologists received 1 hour of PASI training. They were tested before and after the training to evaluate intra-rater variability. The physicians were further tested after training by using a reference photograph.
RESULTS
The mean of each PASI component was underevaluated compared with scoring by a PASI expert. The concordance rate with the expert's grading was highest for thickness followed by erythema, scaling, and area. The scaling score showed the greatest improvement after training. After training, the distribution of deviation from the expert's grading, which signifies inter-rater variability, improved only for the PASI area component. The deviation of scaling grading improved upon retesting by using a reference photograph.
CONCLUSION
PASI assessment training improved variabilities to some degree but not for every PASI component. The development of an objective psoriasis severity assessment tool will help overcome the subjective variabilities in PASI assessment, which can never be completely eliminated via training.

Keyword

Body surface area; Education; Psoriasis; Severity of illness index

MeSH Terms

Body Surface Area
Education
Erythema
Psoriasis*
Severity of Illness Index
Treatment Outcome

Figure

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  Fig. 1 Comparisons of the grading results (A) between the pretest and follow-up retest for mean erythema, thickness, and scaling grades; (B) between the pretest and retest for mean area estimates (%); (C) between the pretest and retest with reference photographs for mean erythema, thickness, and scaling grades. *p<0.05.

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  Fig. 2 Deviations from the expert's grading for the psoriasis area and severity index assessment components in three tests. The left side scale is the y-axis of erythema, thickness, and scaling (grading), and the right side scale is the y-axis of the area (%). *p<0.05.

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  Fig. 3 Coverage area (%) estimation module for psoriasis area and severity index body surface area calculation. When we slide the control bar under the rectangle, the area (%) covered by the circles in the main rectangle changes. The sum of the circle areas represents (A) 10% and (B) 33% coverage of the rectangle. To estimate the area covered by small plaques distributed across a body region, the approximate area (%) can be obtained by sliding the control bar to display a size similar to that of the patient's lesion in the main rectangle.

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