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.