Elevated serum IL-6 levels predict treatment interruption in patients with moderate to severe psoriasis: a 6-year real-world cohort study

Abstract

Background: Real-world, primary data on the treatment of psoriasis are scarce, especially concerning the role of soluble biomarkers as outcome predictors.

Objective: The authors evaluated the utility of Th1/Th17 serum cytokines along with clinical characteristics as predictors of drug survival in the treatment of psoriasis.

Methods: The authors consecutively included participants with moderate to severe psoriasis who were followed up for 6 years. Baseline interferon-α, tumor necrosis factor-α, and interleukin (IL)-2, IL-4, IL-6, IL-10, and IL-17A were measured using a cytometric bead array; clinical data were assessed. The authors calculated hazard ratios (HRs) for drug survival using a Cox proportional hazards model.

Results: The authors included 262 patients, most of whom used systemic immunosuppressants or biologics. In the multivariate model, poor quality of life measured by the Dermatology Life Quality Index (HR = 1.04; 95% CI 1.01‒1.07; p = 0.012) and elevated baseline IL-6 (HR = 1.99; 95% CI 1.29‒3.08; p = 0.002) were associated with treatment interruption.

Study limitations: The main limitation of any cohort study is the presence of confounders that could not be detected in clinical evaluation.

Conclusions: Poor quality of life and elevated baseline serum IL-6 level predicted treatment interruption in patients with moderate to severe psoriasis. Although IL-6 is not the most important mediator of the inflammatory pathway in the skin environment, it is an interesting biomarker candidate for predicting psoriasis treatment response.

Keywords: Allergy and immunology; Autoimmune disease; Biomarkers; Immunosuppression therapy; Psoriasis.

Figure 1

Serum cytokine levels in psoriasis patients according to the type of basal immunosuppressive therapy at the time of inclusion. Data are shown as a scattering distribution of individual values over bar charts representing the median levels of each cytokine. IL, Interleukin; TNF, Tumor Necrosis Factor; IFN, Interferon; HC, Healthy Controls; No, Psoriasis patients using no systemic immunosuppressors; Classic, Psoriasis patients using classic immunosuppressors; α-TNF, Psoriasis patients using anti-tumor necrosis factor agents; α-IL, Psoriasis patients using anti IL agents; p-values for all groups that presented a significant difference are disclosed at the bottom of each graphic. Non-significant p-values (> 0.05) are not represented.

Figure 2

Serum cytokine levels in psoriasis patients according to drug survival stratified by 1 to 4 years and 5 to 6 years. Data are shown as scattering distribution of individual values over bar charts representing median levels of each cytokine. IL, Interleukin; TNF, Tumor Necrosis Factor; IFN, Interferon; HC, Healthy Controls; p-values for all groups that presented a significant difference are disclosed at the bottom of each graphic. Non-significant p-values (> 0.05) are not represented.

Figure 3

Survival curve showing the joint effect of the two main predictors of drug interruption Interleukin (IL)-6 levels and Dermatology Life Quality Index (DLQI). It can be seen that patients experiencing higher DLQI and IL-6 levels had an almost 75% chance of systemic treatment change in the follow-up period. mIL6, Median IL-6 scores of the present population (0 = below the median value; 1 = above the median value). mDLQI, DLQI score of the present population; 0 = below 5; 1 = above or equal 5.