Comparative Assessment of PASI and Variations of PGA×BSA as Measures of Psoriasis Severity

Abstract

Background

Commonly used instruments for measuring psoriasis, such as Psoriasis Area and Severity Index (PASI), have limitations, including high complexity.

Objective

Determine if PGA×BSA or PGA×√BSA are practical alternatives to PASI for measuring severity and treatment response.

Methods

Data from a Phase 3 study in 1,101 patients treated for moderate to severe psoriasis were used. PASI was the reference standard. Correlations (Pearson coefficients), test-retest reliability (intraclass correlation coefficients), responsiveness to treatment (percentage change and effect size), and correspondence (sensitivity and specificity) were assessed.

Results

Correlation coefficients of change (baseline at Week 12) were 0.90 between PASI and either PGA×BSA and PGA×√BSA. ICCs were 0.90. Both instruments demonstrated similar percentage change from baseline and effect sizes. Sensitivities of PGA×BSA and PGA×√BSA were 99% and 95%, and specificities were 76% and 87%, respectively.

Conclusions

PGA×BSA and PGA×√BSA had similar measurement properties as PASI. PGA×BSA is a practical alternative to PASI.

Keywords

PASI physician's global assessment body surface area psoriasis psoriasis area and severity index severity tofacitinib etanercept

Get full access to this article

View all access options for this article.

References

Boehncke

W.H.

Schon

M.P.

. Psoriasis. Lancet. 2015; 386: 983–994.

Parisi

Symmons

D.P.

Griffiths

C.E.

Ashcroft

D.M.

. Global epidemiology of psoriasis: a systematic review of incidence and prevalence. J Invest Dermatol. 2013; 133: 377–385.

Rachakonda

T.D.

Schupp

C.W.

Armstrong

A.W.

. Psoriasis prevalence among adults in the United States. J Am Acad Dermatol. 2014; 70: 512–516.

Kurd

S.K.

Gelfand

J.M.

. The prevalence of previously diagnosed and undiagnosed psoriasis in US adults: results from NHANES 2003-2004. J Am Acad Dermatol. 2009; 60: 21–224.

Feldman

S.R.

Krueger

G.G.

. Psoriasis assessment tools in clinical trials. Ann Rheum Dis. 2005; 64 Suppl 2: ii65–ii68.

Spuls

P.I.

Lecluse

L.L.

Poulsen

M.L.

Bos

J.D.

Stern

R.S.

Nijsten

. How good are clinical severity and outcome measures for psoriasis?: quantitative evaluation in a systematic review. J Invest Dermatol. 2010; 130: 933–943.

Fredriksson

Pettersson

. Severe psoriasis–oral therapy with a new retinoid. Dermatologica. 1978; 157: 238–244.

European Medicines Agency. Guideline on clinical investigation of medicinal products indicated for the treatment of psoriasis. 2004; EMEA.

Robinson

Kardos

Kimball

A.B.

. 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. J Am Acad Dermatol. 2012; 66: 369–375.

10.

Cappelleri

J.C.

Bushmakin

A.G.

Harness

Mamolo

. Psychometric validation of the physician global assessment scale for assessing severity of psoriasis disease activity. Qual Life Res. 2013; 22: 2489–2499.

11.

van de Kerkhof

P.C.

. On the limitations of the psoriasis area and severity index (PASI). Br J Dermatol. 1992; 126: 205.

12.

Walsh

J.A.

McFadden

Woodcock

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

J Am Acad Dermatol. 2013; 69: 931–937.

13.

Bachelez

van de Kerkhof

P.C.

Strohal

Tofacitinib versus etanercept or placebo in moderate-to-severe chronic plaque psoriasis: a phase 3 randomised non-inferiority trial.

Lancet. 2015; 386: 552–561.

14.

Thomas

C.L.

Finlay

A.Y.

. The ‘handprint’ approximates to 1% of the total body surface area whereas the ‘palm minus the fingers’ does not. Br J Dermatol. 2007; 157: 1080–1081.