MPO and schizophrenia: 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.