Validation of the Simplified Psoriasis Index in Dutch children and adolescents with plaque psoriasis

Summary Background The Simplified Psoriasis Index (SPI) is a three‐domain assessment measure for psoriasis, including separate indicators of current severity (SPI‐s), psychosocial impact (SPI‐p), and past history and interventions (SPI‐i). There are two complementary versions available designed for completion by a health professional (proSPI) or by patient self‐assessment (saSPI). The validity and reliability of the proSPI vs. saSPI have already been demonstrated in adults. To date, validated severity measures for paediatric psoriasis do not exist. Objectives To validate the current severity (SPI‐s) and psychosocial impact (SPI‐p) domains of the proSPI and saSPI in children and adolescents with psoriasis. Methods All patients aged < 18 years with plaque psoriasis visiting the dermatology outpatient department of Radboud University Medical Center, the Netherlands, between September 2013 and April 2014 were asked to complete Dutch versions of the saSPI and the Children's Dermatology Life Quality Index (CDLQI). The original English versions of the proSPI and Psoriasis Area and Severity Index (PASI) were completed by the physician at the same visit. Results In total, 113 patients (median age 12·0 years, range 4–17) were included. There was a close correlation between the proSPI‐s and PASI (r = 0·87), which was higher than between the saSPI‐s and PASI (r = 0·69). The correlation between the SPI‐p and CDLQI was 0·78. The full range of scores was utilized in both proSPI‐s and SPI‐p, although the highest saSPI‐s score was 30 (maximum 50). Conclusions In paediatric psoriasis, the proSPI and saSPI are shown to be valid and usable. The SPI‐s and SPI‐p can be readily introduced into routine clinical practice. What's already known about this topic? Validated severity measures do not exist for psoriasis in children and adolescents. The Simplified Psoriasis Index (SPI) is a summary measure of psoriasis, with separate domains for current severity and psychosocial impact. Its validity and reliability has been demonstrated in adults in professionally assessed (proSPI) and patient self‐assessment (saSPI) versions. What does this study add? Both the proSPI and saSPI are valid for use in children and can be readily introduced into routine practice.