The Salford Psoriasis Index: an holistic measure of psoriasis severity

We have developed, tested and validated a new scoring system for psoriasis: the Salford Psoriasis Index (SPI). The SPI incorporates the current clinical extent of psoriasis based on the Psoriasis Area and Severity Index (PASI), a score indicating psychosocial disability, and past severity based on treatment history. The resultant three-figure SPI (signs, psychosocial disability, interventions) is a similar paradigm to the TNM (tumour, nodes, metastasis) classification used for cancer staging. The first figure transforms the PASI into a number from 0 to 10 reflecting extent of psoriasis. The second assesses the psychosocial impact of psoriasis on each patient using a 0-10 visual analogue scale. The third figure reflects historical severity of disease as judged by the need for systemic treatment, admission to hospital and number of episodes of erythroderma. The SPI was prospectively employed in assessing 150 consecutive patients with psoriasis. Furthermore, in a separate cohort of 100 patients we tested the Psychosocial Impact Score against a recognized self-report psoriasis-specific measure, the Psoriasis Disability Index. There was a strong correlation between the two (r = 0.59, P < 0.001). However, the Psychosocial Impact Score correlated poorly with clinical extent scores such as the PASI (r = 0.28, P < 0.05) and the Self-administered PASI in 72 patients tested (r = 0.19, P = 0.1). There was a high correlation between all six observers in 20 patients for both PASI (r = 0.71; 95% confidence interval, CI 0.51-0.86) and the Extent Score (r = 0.70; 95% CI 0. 56-0.89). We believe that the SPI will be more relevant to real-life categorization of psoriasis severity in that it takes an holistic approach based not only on physician assessment but also psychological disability and treatment resistance.