Facial Psoriasis Log-based Area and Severity Index: A valid and reliable severity measurement method detecting improvement of facial psoriasis in clinical practice settings

Drug survival reflects a drug's effectiveness, safety, and tolerability. We assessed the drug survival of biologics used to treat psoriasis in a prospective national pharmacovigilance cohort (British Association of Dermatologists Biologic Interventions Register (BADBIR)). The survival rates of the first course of biologics for 3,523 biologic-naive patients with chronic plaque psoriasis were compared using survival analysis techniques and predictors of discontinuation analyzed using a multivariate Cox proportional hazards model. Data for patients on adalimumab (n=1,879), etanercept (n=1,098), infliximab (n=96), and ustekinumab (n=450) were available. The overall survival rate in the first year was 77%, falling to 53% in the third year. Multivariate analysis showed that female gender (hazard ratio (HR) 1.22; 95% confidence interval (CI): 1.09-1.37), being a current smoker (HR 1.19; 95% CI: 1.03-1.38), and a higher baseline dermatology life quality index (HR 1.01; 95% CI: 1.00-1.02) were predictors of discontinuation. Presence of psoriatic arthritis (HR 0.82; 95% CI: 0.71-0.96) was a predictor for drug survival. As compared with adalimumab, patients on etanercept (HR 1.63; 95% CI: 1.45-1.84) or infliximab (HR 1.56; 95% CI: 1.16-2.09) were more likely to discontinue therapy, whereas patients on ustekinumab were more likely to persist (HR 0.48; 95% CI: 0.37-0.62). After accounting for relevant covariates, ustekinumab had the highest first-course drug survival. The results of this study will aid clinical decision making when choosing biologic therapy for psoriasis patients.

Reliable assessment of severity in psoriasis is essential to document treatment responses in clinical research. The reliability of current clinical outcome measures is uncertain. To quantify the relative variation in commonly used outcome measures (the Psoriasis Area and Severity Index [PASI] and one version of the Psoriasis Global Assessment [PGA]), and a newer measure, the Lattice System Physician's Global Assessment (LS-PGA). Physicians who were experienced (53%; 9/17) or inexperienced (47%; 8/17) in using PASI and PGA evaluated 35 patients with psoriasis in random order twice with each rating system. We assessed the variation in scoring psoriasis severity within (intrarater) and among (interrater) physicians. PASI, PGA, and LS-PGA were highly correlated (r > 0.8 for all comparisons) and had high overall reliability (Cronbach's alpha > 0.9 for each). PGA and LS-PGA had lower intrarater variation than PASI. LS-PGA had a 55% higher concordance coefficient between the two evaluations than did PGA. Interrater variation was lower for PGA and LS-PGA than for PASI both before and after correction for measurement error. Experience was beneficial in reducing variation in PASI scores but was not required with PGA or LS-PGA. The LS-PGA, which is standardized, does not require experience, and provides discrete word-based scores with intrinsic meaning, is a reliable measure of therapeutic effect in psoriasis, and would allow comparisons across different clinical trials.

A wide variety of scoring systems have been proposed to assess severity of psoriasis. Given its importance as a health issue both for patients and health care systems, it is critically important to evaluate the validity and reliability of existing outcome measures. The objective of this systematic review was to assess the extent of validation including the validity, reliability, sensitivity to change and ease of use of available outcome measures for psoriasis. We conducted a systematic review of all clinical studies (prospective and retrospective) investigating the severity of psoriasis patients and published between January 1980 and June 2009. The following methodological validation and quality criteria were recorded systematically: construct validity, content validity and internal consistency, intra-observer variation and inter-observer variation, sensitivity to change and acceptability/ease of use assessed as time required to perform measurement. Based on methodological validation and quality criteria, six clinical severity scores were selected and analysed (PASI, BSA, PGA, LS-PGA, SPI and SAPASI scores). We did not find substantial evidence of construct validity for any of the psoriasis clinical severity scores. Content validity was studied by considering the PASI score as gold standard. The relative content validity was good for the LS-PGA, PGA, and SPI scores, which correlated strongly with the PASI score. The SAPASI and PASI scores showed moderate correlation. Internal consistency was good for the PASI and LS-PGA scores. The PASI, BSA, PGA and LS-PGA scores displayed limited intra-observer variation. The inter-observer variation was low for LS-PGA (ICC 0.8). The PASI score and the SAPASI displayed moderate sensitivity to change. Based on this systematic review, it appears that none of the severity scores used for psoriasis meets all of the validation criteria required for an ideal score. However, we can conclude that the PASI score is the most extensively studied psoriasis clinical severity score and the most thoroughly validated according to methodological validation criteria. Despite certain limitations, use of the PASI score can be recommended for scientific evaluation of the clinical severity of psoriasis.