Original article
Product of the Physician Global Assessment and body surface area: A simple static measure of psoriasis severity in a longitudinal cohort

Portions of these data were presented at the Society for Investigative Dermatology 71st Annual Meeting, Phoenix, Arizona, May 4-7, 2011.
https://doi.org/10.1016/j.jaad.2013.07.040Get rights and content

Background

The Psoriasis Area and Severity Index (PASI) is considered the gold standard assessment tool for psoriasis severity, but PASI is limited by its complexity and insensitivity in people with mild psoriasis.

Objective

We sought to evaluate the product of a Physician Global Assessment (PGA) and Body Surface Area (BSA) (PGAxBSA) as an alternative to PASI.

Methods

Psoriasis severity was evaluated at 6-month intervals in participants of the Utah Psoriasis Initiative registry. Correlation coefficients were used to compare PGAxBSA with PASI and the Simplified PASI (SPASI).

Results

Between August 2008 and November 2010, 435 assessments were completed in 226 participants. The median PASI score was 3.2 (interquartile range 1.8-5.4) and the median BSA was 3.0% (interquartile range 1.0%-5.0%). PGAxBSA had higher correlations with PASI than SPASI (0.87 vs 0.76, P < .001). PGAxBSA also had higher correlations with a Global Patient Assessment of psoriasis severity (0.65) than both PASI (0.59, P < .001) and SPASI (0.51, P < .001).

Limitations

The use of PGAxBSA for measuring severe psoriasis and response to therapy is unclear, because most participants had mild to moderate psoriasis and data were not collected at predefined intervals in relation to therapy initiation. Interrater reliability was not assessed.

Conclusions

PGAxBSA is a simple and sensitive instrument for measuring psoriasis severity.

Section snippets

Methods

This cohort study was designed to assess the validity of PGAxBSA relative to PASI and SPASI. Data from the Utah Psoriasis Initiative were used. The Utah Psoriasis Initiative is a registry of over 1200 consecutively enrolled patients with psoriasis. Participants were evaluated at 6-month intervals between August 2008 and November 2010 by 3 dermatology investigators. Each investigator was trained by a psoriasis expert with extensive experience in educating investigators on psoriasis severity

Patient demographics

The analyses were performed on 435 patient evaluations from 226 participants. The static disease assessments were performed with 435 evaluations and the responsiveness to change analyses were performed with 240 evaluations. The average age of participants at entry to the study was 50 ± 15 years, and 113 (50%) were male (Table II). Caucasian race was reported in 206 (91%) participants. The average disease duration, at entry, was 23 ± 15 years. The median PASI score was 3.2 (interquartile range

Discussion

We explored the validity of PGAxBSA by comparing it with PASI, SPASI, and a patient-derived instrument (GPA) in the setting of a psoriasis registry. PGAxBSA correlated well with PASI and GPA and was sensitive in patients with mild disease. In addition, our data demonstrated that the PGAxBSA may function well as a measure of disease change.

Other instruments have previously been evaluated as alternatives to PASI. The Lattice Systemic PGA,12 the Psoriasis Exact Area and Severity Index,8 and the

References (17)

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Supported by the University of Utah Study Design and Biostatistics Center, with funding in part from the National Center for Research Resources and the National Center for Advancing Translational Sciences, National Institutes of Health, through Grant 8UL1TR000105 (formerly UL1RR025764). Dr Gelfand received funding from the National Institute of Arthritis and Musculoskeletal and Skin Diseases, through Grant K24AR064310. Dr Duffin received funding from the National Institutes of Health grant 1KM1CA156723.

Conflicts of interest: None declared.

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