Evaluation of Inflammatory and Oxidative Markers and Their Diagnostic Value in Schizophrenia

Objective: Schizophrenia is a chronic psychiatric disorder associated with increased oxidative stress. We aimed to investigate serum myeloperoxidase (MPO), catalase (CAT), and malondialdehyde (MDA) levels and their diagnostic value in schizophrenia. Methods: Sixty patients with schizophrenia, diagnosed according to DSM-V criteria, and 65 age- and sex-matched healthy controls were enrolled. Clinical severity was assessed with the Positive and Negative Syndrome Scale (PANSS) and Clinical Global Impression (CGI). Serum MPO and CAT were measured using ELISA, and MDA levels were determined spectrophotometrically. Receiver operating characteristic (ROC) analysis was performed to assess diagnostic performance. Results: Compared with controls, schizophrenia patients demonstrated significantly higher serum MDA (5.64 vs. 3.42 pg/mL, p < 0.001), MPO (77.25 vs. 31.42 ng/mL, p < 0.001), and CAT (22.06 vs. 6.58 ng/mL, p < 0.001) levels. Subgroup analysis revealed consistently increased values across patients receiving typical, atypical, or combined antipsychotics. ROC analysis indicated good diagnostic accuracy: AUC = 0.884 for MDA (cut-off: 3.79 pg/mL), AUC = 0.882 for MPO (cut-off: 34.56 ng/mL), and AUC = 0.875 for CAT (cut-off: 9.38 ng/mL), all p < 0.001. Combined analysis of MPO, CAT, and MDA yielded superior diagnostic performance (AUC = 0.995; sensitivity = 98.3%). MPO was positively correlated with PANSS-N scores (r = 0.275, p = 0.033), and both MPO and CAT were correlated with CGI severity scores. Conclusions: Elevated MPO, CAT, and MDA levels indicate increased oxidative stress in schizophrenia. MPO may also be associated with negative symptom severity. These findings suggest potential utility of oxidative stress biomarkers as adjunctive diagnostic tools, although results should be considered preliminary and validated in larger, drug-naïve, and longitudinal samples.