Original article
Physician Global Assessment (PGA) and Psoriasis Area and Severity Index (PASI): Why do both? A systematic analysis of randomized controlled trials of biologic agents for moderate to severe plaque psoriasis

A small portion of these data was presented as a poster abstract at the Society for Investigative Dermatology 71st Annual Meeting, Phoenix, Arizona, May 4-7, 2011.
https://doi.org/10.1016/j.jaad.2011.01.022Get rights and content

Background

Although there are many psoriasis assessment tools currently published, one of the unmet needs in psoriasis research remains consensus about the single best validated and reproducible assessment tool.

Objectives

In this systematic review we sought to determine the degree of correlation between two commonly used psoriasis assessment tools, the Psoriasis Area and Severity Index (PASI) and Physician Global Assessment (PGA).

Methods

Randomized controlled systemic trials in moderate to severe psoriasis were reviewed using the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. We recorded and compared the percent of patients achieving both 75% reduction in PASI score (PASI 75) and PGA 0 or 1 (clear or almost clear) at 8 to 16 weeks, 17 to 24 weeks, and greater than 24 weeks of treatment with the investigational drug.

Results

Our literature review yielded 30 randomized controlled trials using biologic agents in moderate to severe psoriasis. We found that the two assessment tools correlate very tightly except at the lower bounds of therapeutic efficacy. The r2 values for the correlation between PASI 75 and a score of clear or almost clear on the PGA were 0.9157 at 8 to 16 weeks and 0.892 at 17 to 24 weeks.

Limitations

Limitations of our study include the small number of randomized controlled trials publishing the percent of patients achieving 75% reduction in PASI score and a score of clear or almost clear on the PGA after 24 weeks of therapy. In addition, our results are not generalizable beyond the patients with moderate to severe plaque psoriasis.

Conclusion

The two assessment tools are substantially redundant and either alone is a sufficient tool for assessing psoriasis severity in patients with moderate to severe disease. Because the PASI is better validated and more detailed, it remains the score of choice for clinical trials, but the simpler PGA may be well suited for community-based outcomes projects.

Section snippets

Methods

We investigated how well the PGA correlates with the PASI to determine whether or not they provide redundant clinical information regarding disease severity. Following the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines for performing a systematic review, a literature search protocol was developed. The Ovid MEDLINE database was used to search for randomized controlled trials for 7 biologic therapies, phototherapy, cyclosporine, and methotrexate. The search terms

Results

Of the 123 studies reviewed, 30 met inclusion criteria. In general, studies of the nonbiologic drugs performed before 2000 did not use both PASI and PGA as assessment tools. There was only one study of a topical therapy that did report the percentage of patients achieving a PGA 0,1 and PASI 75.38 Thus, our results were limited to 30 randomized controlled trials of biologic drugs from 2001 through 2010. The percentage of patients achieving a PASI 75 was compared with the percentage of patients

Discussion

The PASI is the most commonly used and best validated psoriasis severity assessment tool. However, the majority of clinical trials performed within the past 10 years for moderate to severe psoriasis use both the PASI and PGA as measures of severity. This may in part be a result of recommendations from the FDA that accept the PASI, but emphasize its shortcomings. The two assessment tools have previously been compared directly in a single trial and found to correlate well.39 The results of this

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    Funding sources: National Psoriasis Foundation/USA.

    Conflicts of interest: None declared.

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