Relationship between blood-based inflammatory indices and clinical score of schizophrenia patients: A cross-sectional study

Schizophrenia is a severe mental disorder that may involve inflammation. Inflammatory indices, such as the neutrophil to lymphocyte ratio (NLR), the monocyte to lymphocyte ratio (MLR), the platelet to lymphocyte ratio (PLR), and the systemic inflammation index (SII), are simple and inexpensive measures of inflammation that have been associated with various diseases. However, few studies have compared these indices and their relationships with clinical symptoms in schizophrenia. We conducted a cross-sectional study of 121 schizophrenia patients (101 males, 20 females). We measured the blood-based inflammatory indices (NLR, MLR, PLR, and SII) and assessed the clinical symptoms of schizophrenia using the Positive and Negative Syndrome Scale (PANSS). Statistical analyses were performed to examine the correlations and effects of the inflammatory indices on PANSS scores. We found that NLR, MLR, PLR, and SII were positively correlated with PANSS total score, PANSS positive score, PANSS negative score, and general psychopathology score (adjusted P < 0.02 for all correlations). Subgroup analysis showed that correlations between inflammatory indices and the clinical scores differed by gender. In males, all inflammatory indices were positively correlated with all clinical scores. On the other hand, in females, only NLR and SII were positively correlated with all clinical scores. After adjusting for confounders, we also found that NLR was a predictor of PANSS total score (β = 23, adjusted P < 0.02), PANSS positive score (β = 2.6, adjusted P = 0.03), PANSS negative score (β = 6.8, adjusted P < 0.02), and PANSS general psychopathology score (β = 13.6, adjusted P < 0.02), while SII was only a predictor for PANSS total score (β = -0.00003, adjusted P = 0.01) and general psychopathology scores (β = -0.00002, adjusted P < 0.02). These findings suggest that inflammation is involved in the pathophysiology and clinical manifestations of schizophrenia, and that blood-based inflammatory indices may serve as screening tools or indicators for the inflammatory status and severity of symptoms of schizophrenia patients.