Background: Psoriasis Area and Severity Index (PASI) 90 is suggested to be the new standard endpoint for randomized controlled trials of biologics for psoriasis, whereas treatment guidelines often still refer to PASI 75.
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 na€ıve patients with PASI, Dermatology Life Quality Index (DLQI) and EuroQol (EQ)-5D outcomes before (maximum 6 months) and after (3–12 months) switch to biologics during registration in the Swedish National Registry 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 percentage response levels.
Results: High PASI percentage response was associated with higher PASI before switch and lower body mass index. DLQI and EQ-5D improved within all responder groups (P < 0001). The magnitude of improvements in DLQI (P = 002) differed between responder groups. The mean (SD) DLQI improvements for PASI 75<90 responders, PASI 90<100 responders and patients achieving complete skin clearance (PASI 100) were 99 (74), 115 (70) and 80 (61), respectively.
Conclusions: 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 PASI 90 are thus not suitable for treatment guidelines or for follow-up in clinical practice.