Analysis of Three Outcome Measures in Moderate to Severe Psoriasis: a Registry-based Study of 2450 Patients

Background: As moderate to severe psoriasis is a systemic disease with large effects on health-related quality of life, generic measures that include overall health, not only skin involvement, are necessary. Knowledge about the relationship between the generic preference-based EuroQol 5D (EQ-5D) and dermatology-specific measures in psoriasis is limited.

Objectives: To analyse EQ-5D, the Dermatology Life Quality Index (DLQI) and the Psoriasis Area and Severity Index (PASI) in patients with moderate to severe psoriasis in Swedish clinical practice by demographic characteristics, to compare EQ-5D among patients vs. Swedish population values, and to analyse the relationships between EQ-5D, DLQI and PASI.

Methods: This observational cohort study was based on PsoReg, the Swedish National Registry for Systemic Treatment of Psoriasis. EQ-5D was compared among patients with psoriasis vs. a defined general population in Sweden, retrieved from a previous study. Relationships between measures were examined with correlation tests and regression analysis.

Results: In total, 2450 patients (1479 men and 971 women) were included. Median EQ-5D, DLQI and PASI scores were 0·769, 4 and 4·7, respectively. Patients with psoriasis had a significantly lower EQ-5D compared with the defined general population. EQ-5D correlated moderately with DLQI (-0·55) and weakly with PASI (-0·25) (P < 0·001).

Conclusions: When assessing psoriasis treatments and making decisions about treatment guidelines and resource allocation, EQ-5D, DLQI and PASI provide a useful set of complementary tools, answering to different needs. If EQ-5D is not included in the original trial the second-best option in cost-effectiveness studies is to use mapping between DLQI and EQ-5D.