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 (PAST) 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 PAST. Methods This observational cohort study was based on PsoReg, the Swedish National Registry for Systemic among patients with psoriasis retrieved from a previous study Treatment of Psoriasis. EQ-5D was compared vs. a defined general population in Sweden, 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 PAST (-0-25) (P < 0.001). Conclusions When assessing psoriasis treatments and making decisions about treat merit guidelines and resource allocation, EQ-5D, DLQI and PAST 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.