BACKGROUND: PASI90 is suggested to be the new standard endpoint RCTs of biologics for psoriasis, whereas treatment guidelines often still refer to PASI75.

OBJECTIVES: To analyse in a real-world setting: Firstly, what factors are associated with higher levels of treatment response to biologics. Secondly, the Health-Related Quality of Life gains associated with different response levels in clinical practice.

METHODS: Biologically-naïve patients with PASI, DLQI and EQ-5D outcomes before (maximum 6 months) and after (3-12 months) switch to biologics during registration in the Swedish Register for systemic treatment of psoriasis, PsoReg, were included (n=515). Patient characteristics associated with higher treatment response were analysed by regression analyses. Improvements in absolute PASI, DLQI and EQ-5D were assessed in different PASI percent response levels.

RESULTS: High PASI percentage response was associated with higher PASI before switch and lower BMI. DLQI and EQ-5D improved within all responder groups (p<0·001). The magnitude of improvements in DLQI (p=0·02) differed between responder groups. The mean (SD) DLQI improvement for PASI75-<90, PASI90-<100 responders and patients achieving Complete Skin Clearance (PASI100) were 9·9 (7·4), 11·5 (7·0) and 8·0 (6·1), respectively.

CONCLUSION: PASI percentage change is largely dependent on absolute PASI before switch. Patients in clinical practice lack "baseline" PASI values as they may switch directly from one treatment to another or stay successfully treated for a longer time period. Treatment goals such as PASI90 are thus not suitable for treatment guidelines or for follow-up in clinical practice.