Exploring the relationship between EQ-5D, DLQI and PASI, and mapping EQ-5D utilities: a cross-sectional study in psoriasis from Hungary.

Background: There is a growing interest in policy making for using utility measures and identifying algorithms to convert disease-specific measures into utilities.

Objectives: To analyse the relationship between EQ-5D, Dermatology Life Quality Index (DLQI) and Psoriasis Area and Severity Index (PASI) in psoriasis. To transform DLQI scores, and key clinical, demographic and health service utilisation variables into utilities.

Methods: A cross-sectional questionnaire survey of 200 consecutive adult patients with moderate to severe psoriasis was carried out in two Hungarian university clinics. The relationship between the outcome measures were analysed with correlations and with the known-groups method. Bivariate and multivariate regression algorithms on EQ-5D scores were formulated.

Results: The mean age of respondents was 51 years (SD = 12.9), 68.5% were male, and 51.5% received biological therapy. Median EQ-5D, DLQI, and PASI scores were 0.73, 3.0, and 3.45, respectively. EQ-5D showed a moderate correlation with the DLQI and with the PASI (r s = -0.48 and -0.43, p < 0.05). Strong correlation was found between DLQI and PASI (r s = 0.81, p < 0.05). DLQI and PASI discriminated better among groups categorised by the localisation of the lesions than EQ-5D. Presence of psoriasis on the neck and/or décolletage was associated with the greatest health related quality of life (HRQOL) impairment. Ten variables were incorporated in a multivariate algorithm that accounted for 48.8% of EQ-5D variance (ANOVA p < 0.001).

Conclusions: This study provided the first evidence that patients with visible psoriatic lesions have significantly worse HRQOL compared to those with non-visible lesions, measured not only with DLQI but also with EQ-5D. In addition to demographic and clinical variables, our model included health service utilisation variables related to psoriasis, and explained higher proportion of EQ-5D variance than any previous findings in the literature.