Interleukin-5, Eosinophil, and Immunoglobulin A Levels in Schizophrenia Patients.

Objective: To analyze the correlation between interleukin-5 (IL-5), eosinophils (EOS), and immunoglobulin A (IgA) levels with schizophrenia, and assess their potential as auxiliary diagnostic markers for schizophrenia.

Methods: This study comprised 57 patients with first-episode schizophrenia and 340 patients with recurrent or chronic schizophrenia who were hospitalized at Beijing Huilongguan Hospital from March 2023 to August 2024, and 72 healthy volunteers were recruited as the control group. Fasting venous blood samples were collected from all participants on the second day after admission. For patients with first-episode schizophrenia, a second blood draw was performed after two months of treatment. Simultaneously, the Positive and Negative Symptom Scale (PANSS) was administered to assess the subjects. IL-5 and EOS levels were measured using flow cytometry; IgA levels were measured using immunoturbidimetry. SPSS v.29.0 was used to conduct t-tests, one-way ANOVA, correlation analysis and receiver operating characteristic (ROC) curve analysis.

Results: The first-episode schizophrenia group and the recurrent/chronic schizophrenia group had elevated IL-5 levels relative to healthy controls; however, the increase in EOS levels was specifically observed in the recurrent/chronic schizophrenia group. After treatment, the IL-5 level in the first-episode group was markedly reduced. Correlation analysis revealed that in patients with schizophrenia, IL-5 levels were positively correlated with EOS (r = 0.338, p < 0.001), and EOS levels were positively associated with disease duration (r = 0.171, p < 0.05), the ROC curve analysis revealed that IL-5 had a sensitivity of 52.9%, specificity of 69.4%, and a cut-off value of 2.445 pg/mL for predicting schizophrenia.

Conclusion: In patients with schizophrenia, the elevated levels of IL-5 and EOS appear to be disease-related rather than medication-induced, suggesting their potential involvement in the inflammatory pathogenesis of schizophrenia. Furthermore, IL-5 exhibits greater predictive accuracy for schizophrenia compared to EOS, suggesting that IL-5 may serve as a valuable biomarker for auxiliary diagnosis and stratification analysis in schizophrenia.