Background: There is a need to evaluate severity of psoriasis with a simple, patient-assessed instrument. Objective: To investigate whether the self-administered Psoriasis Area and Severity Index (SAPASI) could be used as a measure of severity in different clinical types of psoriasis. Design: Hospital-based cross-sectional study, with measures of clinical severity collected separately by dermatologists (PASI) and patients with psoriasis (SAPASI). Setting: Part of a large project on clinical, epidemiological, emotional, and quality-of-life aspects of psoriasis (the IDI Multipurpose Psoriasis Research on Vital Experiences study), performed between February 21 and August 31, 2000, at the inpatient wards of the Istituto Dermopatico dell'Immacolata-Istituto di Ricovero e Cura a Carattere Scientifico (IDI-IRCCS), Rome, Italy. Patients: The study population comprised 351 eligible patients with complete sets of information on PASI and SAPASI hospitalized at IDI-IRCCS with a diagnosis of psoriasis. Main Outcome Measures: Correlation between PASI and SAPASI scores and analysis of variance on the difference between PASI and SAPASI scores in subsets of patients based on clinical and sociodemographic characteristics. Results: A high correlation between the 2 measures was observed (overall Pearson correlation coefficient, r=0.69). The SAPASI values were higher and had a wider scattering than PASI values, and SAPASI was able to discriminate properly between clinical types and global severity as assessed by dermatologists. Conclusions: The SAPASI scoring system is well understood and accepted by patients in different populations than previously tested, adding confidence in the validity of the instrument. It could be used as a severity measure for psoriasis even for "at-distance" follow-up. Some caution, though, is needed when using SAPASI strictly to estimate PASI measurements, especially for guttate psoriasis.
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