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

Abstract

BackgroundSeverity 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.ObjectiveIn 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.MethodsTwenty-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.ResultsThe 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.ConclusionPASI 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.

Severity and Area Score for Hidradenitis ( SASH ): a novel outcome measurement for hidradenitis suppurativa

“…48 Studies of psoriasis outcome instruments showed significant improvement in reliability after training. 49,50 The intrarater, or test-retest, reliability of the SASH was very high at 0Á98 (95% CI 0Á94-1Á00) and in this study was higher than all other outcome instruments. The intrarater reliability of the AN count in this study was 0Á89 (95% CI 0Á68-0Á97), which is similar to the estimate from an earlier study [0Á92 (95% CI 0Á83-0Á97)].…”

“…Lastly, inter‐rater reliability can be improved with rater training, such as an online didactic and scored practice session . Studies of psoriasis outcome instruments showed significant improvement in reliability after training …”

Calcipotriol/betamethasone ointment compared to narrow‐band UVB in plaque psoriasis: first clinical and ultrasonographic study

“…Although we did not assess the inter‐ and intra‐rater agreement on the PASI scale in the current study, many studies have reported high rates of disagreement; for this reason, PASI scores may not be fully reliable, especially when assessing patients with scores around 3 . In this sense, the PASI score seems to be a subjective measure, with substantial intra‐ and inter‐rater variability, particularly in evaluating erythema . The subjective nature of PASI scoring is an important drawback, and more objective, standardized methods are needed to more reliably determine psoriasis severity to select the most appropriate treatment.…”

Medical Informatics applied in psoriasis diagnosis and management

“…One practical method of assessing the severity of the disease and among the first ones was described in 1978 by Fredriksson and Pettersson and named PASI (Psoriasis Area and Severity Index) [4]. Even though there are reports which state the fact that this method is based on approximation made using subjective observation -thus with a high inter-rater and intrarater variability of the results [5], or that the method is not sensitive enough. Another major objection for using PASI in clinical assessment is the fact that is too time consuming due to the relatively complex way of calculation [6].…”