Performance of the Self-administered Psoriasis Area and Severity Index in Evaluating Clinical and Sociodemographic Subgroups of Patients With Psoriasis

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.