Supplementary Material for: Translation and validation of the Self-Assessment Psoriasis Area Severity Index (SAPASI)

Background: The Self-Assessment Psoriasis Area Severity Index (SAPASI) is a patient-administered psoriasis assessment tool for which we present a validated translation from English to Swedish.
Methods: Validity was evaluated in this single-centre study using the Psoriasis Area Severity Index (PASI) as the standard. Test-retest reliability was assessed using repeated SAPASI measurements.
Results: Significant correlations (P<0.0001) using Spearman’s correlation coefficient (r) were found between PASI and SAPASI scores (r=0.60) for 51 participants (median baseline PASI 4.4, interquartile range [IQR] 1.8–5.6) and repeated SAPASI measurements (r=0.70) among 38 participants (median baseline SAPASI 4.0, IQR 2.5–6.1). Bland-Altman plots showed generally higher SAPASI scores than PASI scores.
Conclusion: The translated version of SAPASI is valid and reliable, although patients generally tend to overrate their disease severity compared to PASI. Keeping this limitation in mind, SAPASI has the potential of being implemented as a time- and cost-efficient assessment tool in a Scandinavian context.