Comparison of three methods for measuring psoriasis severity in clinical studies (Part 2 of 2): use of quality of life to assess construct validity of the Lattice System Physician's Global Assessment, Psoriasis Area and Severity Index and Static Physician's Global Assessment.
BACKGROUND
Systems for determining psoriasis severity in clinical trials have not been sufficiently validated against patients' perceived quality of life.


OBJECTIVE
To validate three systems of physician-determined psoriasis severity (the Lattice System Physician's Global Assessment [LS-PGA], Psoriasis Area and Severity Index [PASI] and static Physician's Global Assessment [sPGA]).


METHODS
Data were from a 24-week randomized, double-blind, placebo-controlled, multicenter trial of therapy with oral calcineurin inhibitors in 445 patients. Construct validity was measured by correlations of the three severity scores with patients' self-reported quality of life (QoL) from the Dermatology Life Quality Index (DLQI) and a DLQI item about psoriasis symptoms.


RESULTS
All severity systems were moderately and positively correlated with QoL, indicating construct validity. QoL was most consistently related to physicians' assessments of body surface area involved with psoriasis (iBSA) followed by, in the order of consistency, plaque elevation, erythema and scale.


CONCLUSIONS
The LS-PGA weights iBSA and aspects of plaque morphology in concert with their relative effects on QoL. The LS-PGA, sPGA and PASI are validated by their relationship to QoL in a clinical trial.
Department of Dermatology, University of Michigan Medical School, Ann Arbor, Michigan, USA.|Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor, Michigan, USA.
M J
MJ
Simpson
Department of Dermatology, University of Michigan Medical School, Ann Arbor, Michigan, USA.
C
C
Chow
Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor, Michigan, USA.|Department of Environmental Health Sciences, School of Public Health, University of Michigan, Ann Arbor, Michigan, USA.|Department of Urology, University of Michigan Medical School, Ann Arbor, Michigan, USA.
H
H
Morgenstern
Department of Dermatology, University of Münster, Münster, Germany.
T A
TA
Luger
Department of Dermatology, University of Michigan Medical School, Ann Arbor, Michigan, USA.
C N
CN
Ellis
D000284:Administration, Oral; D065095:Calcineurin Inhibitors / Q000008:administration & dosage*; D002983:Clinical Competence; D016572:Cyclosporine / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007166:Immunosuppressive Agents / Q000008:administration & dosage; D008297:Male; D010820:Physicians / Q000592:standards*; D011565:Psoriasis / Q000175:diagnosis / Q000188:drug therapy* / Q000523:psychology; D011788:Quality of Life; D012720:Severity of Illness Index; D013997:Time Factors
D065095:Calcineurin Inhibitors; D007166:Immunosuppressive Agents; C484071:voclosporin; D016572:Cyclosporine