Itching is a significant problem and a mediator between disease severity and quality of life for patients with psoriasis: results from a randomized controlled trial.

BACKGROUND

In patients with moderate-to-severe psoriasis, health-related quality of life (HRQOL) has been shown to improve in parallel with improvement in disease severity.

OBJECTIVES

To evaluate the role of pruritus (itch) in mediating the relationship between improvements in disease severity and HRQOL.

METHODS

Data from a phase 2 clinical trial, in which 142 patients with moderate-to-severe plaque psoriasis received ixekizumab or placebo, were used for this posthoc analysis. Relationships between improvement in Psoriasis Area and Severity Index (PASI), Itch Visual Analogue Scale (VAS) and Dermatology Life Quality Index (DLQI), as well as in individual DLQI domains (symptoms and feelings, treatment, work and school, daily activities, leisure, and personal relationships) from baseline to week 16 were determined. Multiple hierarchical linear regressions and Sobel tests were conducted to evaluate the results.

RESULTS

Improvement in PASI was highly correlated with pruritus improvement and improvements in DLQI total and domain scores at week 16 (P < 0·01). Multiple hierarchical linear regression analyses showed a statistically significant (P < 0·01) association between improvement in pruritus and improvement in DLQI total score and each of the six DLQI domain scores after adjusting for improvement in PASI. Sobel tests indicated that pruritus had a significant mediation effect (P < 0·05) on the association of PASI improvement with improvement in DLQI total score and all domains except the personal relationships score.

CONCLUSIONS

Pruritus appears to be an important mediator of the association between improvements in disease severity and HRQOL in patients with moderate-to-severe psoriasis.