Background Peripheral blood inflammatory indicators reflect systemic homeostasis during inflammatory responses and immune dysregulation, yet their potential as biomarkers for therapeutic efficacy and prognosis in psoriasis patients receiving biologics warrants further investigation.

Objective To analyze the correlation between baseline peripheral blood inflammatory indicators and psoriasis severity in moderate-to-severe plaque psoriasis patients, and evaluate their predictive value for treatment outcomes with infliximab and secukinumab.

Methods A retrospective analysis was conducted using data from two randomized, double-blind, controlled phase Ⅲ clinical trials at our institution. Patients with moderate-to-severe plaque psoriasis treated with biologics from October 2016 to October 2017 and January 2019 to September 2021 were categorized into three groups: infliximab group, secukinumab group and control group. Neutrophil-to-lymphocyte ratio (NLR), systemic immune-inflammation index (SIRI), and aggregate index of systemic inflammation (AISI) were analyzed at baseline, week 4, and week 12. Correlations between these indices and Psoriasis Area and Severity Index (PASI) scores, as well as their association with therapeutic responses, were evaluated.

Results A total of 39 patients were enrolled, including 10 caes in the infliximab group (age range: 30-61 years; 9 males, 1 female), 22 cases in the secukinumab group (age range: 20-51 years; 19 males, 3 females), and 7 cases in the control group (age range: 24-41 years; all males). Correlation analysis revealed positive associations between PASI scores and SIRI (r = 0.472, P < 0.05) as well as AISI (r = 0.373, P < 0.05). Two-way repeated measures ANOVA demonstrated significant differences in both SIRI and AISI across time dimensions and between groups (P < 0.05). In the time dimension analysis, secukinumab treatment significantly reduced SIRI by 0.28 (95% CI: 0.07 - 0.49) at week 4 and 0.38 (95% CI: 0.17 - 0.69) at week 12 compared to baseline (P < 0.05), while AISI decreased by 91.17 (95% CI: 1.27 - 181.07) and 115.06 (95% CI: 23.23 - 206.89) compared with the control group at weeks 4 and 12, respectively (P < 0.05). In the intergroup comparison, Infliximab showed SIRI reduction of 0.43 (95% CI: 0.01 - 0.84) at week 4 and 0.63 (95% CI: 0.26 - 1.00) at week 12 compared with controls (P < 0.05), with AISI decreasing by 115.92 (95% CI: 11.45 - 220.39) and 170.61 (95% CI: 62.22 - 279.00) at the corresponding time points (P < 0.05); Secukinumab exhibited greater SIRI reduction of 0.52 (95% CI: 0.16 - 0.88) and 0.76 (95% CI: 0.44 - 1.09) at weeks 4 and 12 compared with controls (P < 0.05), along with AISI decrease of 137.21 (95% CI: 45.22 - 229.20) and 198.03 (95% CI: 102.58 - 293.47) at these intervals (P < 0.05).

Conclusion The strong correlation between SIRI/AISI indexes and baseline severity of plaque psoriasis suggests their potential utility as objective biomarkers for disease severity assessment. Both infliximab and secukinumab significantly reduced SIRI and AISI values, with secukinumab demonstrating superior efficacy in AISI reduction. Notably, their comparable long-term anti-inflammatory effects provide critical evidence for optimizing biologic therapies in psoriasis management.