D-serine acts as an endogenous co-agonist at the glycine modulatory site of the NMDA receptor. Significantly decreased D-serine serum levels were reported in patients with schizophrenia in comparison to healthy control subjects. D-serine improved positive and negative symptoms in patients with schizophrenia treated with antipsychotics. We hypothesized that D-serine serum level might be associated with specific characteristics of psychopathology in schizophrenia.

We enrolled fifty patients with schizophrenia into the study. Positive and Negative Syndrom Scale (PANSS) and The Scale for the Assessment of Negative Symptoms (SANS) were used to assess the symptoms of schizophrenia. D-serine serum levels were measured by High Performance Liquid Chromatography.

D-serine serum levels were not associated with PANSS and SANS total and subscales scores in the population of fifty patients. We demonstrated only mild insignificant linear association of PANSS score with D-serine serum level (r=0.20) in the group of men (n=33). The mild insignificant inverse correlation was found in the group of women (n=17) between the total PANSS (r=-0.35) or SANS score (r=-0.30) and D-serine serum level.

We assumed that various biochemical and clinical profiles could lead to identification of specific subtypes of schizophrenia. However, we did not find any significant association between serum D-serine and clinical symptoms in this study. D-serine serum levels had a strong trend to be lower among female patients with schizophrenia as compared to men. The role of gender in the glutamatergic dysfunction associated with schizophrenia deserves further attention.