Objective To analyze the relationship between interleukin-4 (IL-4), C-reactive protein (CRP), and the incidence, severity, and therapeutic efficacy of Dupilumab in atopic dermatitis.

Methods A total of 106 patients with atopic dermatitis treated from February 2022 to November 2023 were retrospectively selected as the study group, and 50 healthy volunteers from the same period were selected as the control group. The levels of IL-4 and CRP were measured at different stages (acute, subacute, chronic) and severities (mild, moderate, severe) in both the study and control groups. Receiver operating characteristic (ROC) curves were used to analyze the diagnostic value of IL-4 and CRP in atopic dermatitis. Spearman analysis was used to assess the relationship between the severity of atopic dermatitis and the levels of IL-4 and CRP in patients. All patients with atopic dermatitis received standardized 16-week treatment with pembrolizumab and were divided into effective and ineffective treatment groups. Changes in IL-4 and CRP levels before treatment and at 4, 8, 12, and 16 weeks of treatment were compared, and the correlation between IL-4, CRP, and treatment efficacy at each time point after treatment was analyzed.

Results The levels of IL-4 and CRP were lowest in the chronic phase, higher in the subacute phase, and highest in the acute phase (P < 0.05), with the mild group showing lower levels than the moderate group, and the moderate group lower than the severe group (P < 0.05). Before treatment, the levels of IL-4 and CRP in the study group were (14.88 ± 3.91) pg/mL and (6.07 ± 3.02) mg/L, respectively, both significantly higher than those in the control group, which were (8.27 ± 1.09) pg/mL and (1.06 ± 0.31) mg/L (P < 0.05). The areas under the curve for IL-4, CRP, and their combined diagnosis of atopic dermatitis were 0.831 (95% CI: 0.763-0.886), 0.776 (95% CI: 0.702-0.839), and 0.882 (95% CI: 0.821-0.928), respectively (P < 0.05). Spearman analysis showed that IL-4 and CRP levels in patients with atopic dermatitis were positively correlated with disease severity (r = 0.643, 0.659, P < 0.05). As treatment time increased, IL-4 and CRP levels gradually decreased, with a statistically significant difference between the effective and ineffective groups (P < 0.05). At all time points before and after treatment, IL-4 and CRP levels in the effective treatment group were lower than those in the ineffective treatment group (P < 0.05). Spearman analysis also showed that IL-4 and CRP levels in patients with atopic dermatitis were positively correlated with treatment efficacy at 12 weeks (r = 0.267, 0.280, P < 0.05) and 16 weeks (r = 0.214, 0.377, P < 0.05).

Conclusion IL-4 and CRP are correlated to the occurrence and development of atopic dermatitis. After treatment with Dupilumab, the levels of IL-4 and CRP in patients significantly decreased. IL-4 and CRP have diagnostic value for atopic dermatitis.