Long-Term Changes in Complete Blood Count-Derived Inflammatory Indices During Risankizumab Treatment for Psoriasis: A 208-Week Multicenter Real-World Study

Background/Objectives: Blood count-derived inflammatory indices have been proposed as accessible biomarkers of systemic inflammation in psoriasis, but their longitudinal behavior during selective interleukin-23 blockade remains uncertain. We evaluated these indices in psoriasis patients treated with risankizumab. Methods: We conducted a multicenter retrospective real-world study (DERMIS), including adults with cutaneous psoriasis, with or without psoriatic arthritis, treated with risankizumab across 10 Italian centers, from national reimbursement up to 1 December 2025. Psoriasis Area and Severity Index (PASI) and complete blood count-derived indices—neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio (MLR), systemic immune-inflammation index (SII), and systemic inflammation response index (SIRI)—were assessed at baseline and at weeks 12, 24, 52, 104, 156, and 208. Analyses used available data and sensitivity cohorts with follow-up at weeks 52, 104, and 208. Results: Among 250 patients, 43 had data at week 208. PASI scores decreased significantly at all follow-up time points. In contrast, systemic indices showed heterogeneous, non-linear trajectories: NLR, SII, and SIRI fluctuated without consistent sustained reductions, whereas MLR remained broadly stable. PLR showed the most reproducible downward trend, with nominal reductions at weeks 24 and 52; after Bonferroni correction across the six repeated visits within PLR, the reduction at week 52 remained statistically significant, whereas the week-24 reduction did not. Body mass index (BMI)-related differences were inconsistent and did not remain significant after Bonferroni correction. Sex, cardiometabolic comorbidities, and previous biological exposure showed no consistent effect. Conclusions: These findings challenge the use of routine blood count-derived indices as reliable biomarkers of cutaneous response to risankizumab.