Treatment response heterogeneity in the predominant negative symptoms of schizophrenia: analysis of amisulpride vs placebo in three clinical trials

BACKGROUND

The extent of heterogeneity in response to the psychopharmacological treatment of negative symptoms is unknown.

AIMS

To examine the extent of heterogeneity in response to the treatment of predominantly negative symptoms of schizophrenia.

METHOD

Data were analyzed from three clinical trials that compared placebo or amisulpride for up to 60days. Trial participants had predominantly negative symptoms of schizophrenia (n=485). Heterogeneity of percentage reduction on the Scale for the Assessment of Negative Symptoms (SANS) was examined with trajectory-group based modeling followed by descriptive statistics and the prediction of trajectory group membership with logistic regression modeling. Analyses were repeated separately for the placebo and amisulpride groups.

RESULTS

Trajectory group-based modeling identified groups of non- (n=297, 61.2%), gradual-moderate (n=135, 27.8%) and rapid- (n=53, 10.9%) responders. At baseline compared to non-responders, rapid-responders had consistently significantly (p<.05) higher SANS total and subscale scores. Percent SANS improvement at endpoint was greatest for the rapid-responders group, a finding that replicated stratifying by placebo and amisulpride treatment groups. Similarly, in the total sample and stratifying by placebo and amisulpride groups, dropout was not significantly associated with trajectory group membership.

CONCLUSIONS

Trajectories of treatment response to the psychopharmacological medication of the negative symptoms of schizophrenia demonstrate substantial heterogeneity. Approximately half of the patients included in our analysis showed little improvement, and the most severely ill at baseline responded the most.

Altered phospholipid metabolism in schizophrenia: a phosphorus 31 nuclear magnetic resonance spectroscopy study

Phospholipid (PL) metabolism is investigated by in vivo 31P magnetic resonance spectroscopy (MRS). Inconsistent alterations of phosphocholine (PC), phosphoethanolamine (PE), glycerophosphocholine (GPC) and glycerophosphoethanolamine (GPE) have been described in schizophrenia, which might be overcome by specific editing techniques. The selective refocused insensitive nuclei-enhanced polarization transfer (RINEPT) technique was applied in a cross-sectional study involving 11 schizophrenia spectrum disorder patients (SZP) on stable antipsychotic monotherapy and 15 matched control subjects. Metabolite signals were found to be modulated by cerebrospinal fluid (CSF) content and gray matter/brain matter ratio. Corrected metabolite concentrations of PC, GPC and PE differed between patients and controls in both subcortical and cortical regions, whereas antipsychotic medication exerted only small effects. Significant correlations were found between the severity of clinical symptoms and the assessed signals. In particular, psychotic symptoms correlated with PC levels in the cerebral cortex, depression with PC levels in the cerebellum and executive functioning with GPC in the insular and temporal cortices. In conclusion, after controlling for age and tissue composition, this investigation revealed alterations of metabolite levels in SZP and correlations with clinical properties. RINEPT 31P MRS should also be applied to at-risk-mental-state patients as well as drug-naïve and chronically treated schizophrenic patients in order to enhance the understanding of longitudinal alterations of PL metabolism in schizophrenia.

Psychometric analysis in support of shortening the Scale for the Assessment of Negative Symptoms

Despite recent emphasis on the measurement and treatment of negative symptoms, studies of the Scale for the Assessment of Negative Symptoms (SANS) identify different symptom clusters, offer mixed support for its psychometric properties and suggest that it is shortened. The current study objective is to examine the psychometric properties of the SANS and the feasibility of a short research version of the SANS. Data were re-analyzed from three clinical trials that compared placebo and amisulpride to 60 days. Participants had chronic schizophrenia and predominantly negative symptoms (n=487). Baseline data were examined with exploratory factor analysis and Item Response Theory (IRT) to identify a short SANS. The short and original SANS were compared: with confirmatory factor analysis at endpoint; and on symptom response with mixed modeling to compare. Results showed that at baseline the SANS consisted of three factors labeled Affective-flattening, Asociality and Alogia-inattentiveness. IRT suggested a short SANS with 11 items and 3 response options. Comparisons of the original and short SANS showed: the short version was a better fit to the data based on confirmatory factor analysis at endpoint; similar significant (p<.001) correlations between the baseline and subsequent scores; similar reliability; and similar significance (p<.05) on response based on mixed modeling. It is concluded that a short SANS is feasible to assess predominantly negative symptoms in chronic schizophrenia in research settings.

Association between genetic polymorphisms of Toll-like receptor 2 (TLR2) and schizophrenia in the Korean population

Immunological dysregulation has been suggested to be involved in the pathogenesis of schizophrenia. Accumulating evidences further implicate that activated inflammatory processes may be particularly relevant for the precipitation of negative and cognitive symptoms of schizophrenia. Toll-like receptor 2 (TLR2) plays an important role in innate immunity by sensing a variety of pathogens and inducing an acquired immunity. In the present study, we investigated whether the coding region of single nucleotide polymorphisms (SNPs) of the TLR2 gene was associated with schizophrenia as well as with clinical symptoms in schizophrenia patients. The study population consisted of 286 Korean schizophrenia patients and 305 Korean control subjects. The assessment of the Scale for the Assessment of Negative Symptoms was used to evaluate the negative symptoms of schizophrenia; the operational criteria checklist was used to measure general psychopathology. We selected two cSNPs [rs3804099 (Asn199Asn) and rs3804100 (Ser450Ser)] considering their heterozygosity and minor allele frequency. SNP genotyping was conducted using direct sequencing. We did not find any significant associations between SNPs and schizophrenia in the genotype and allelic frequencies. On the other hand, in the analysis of cognitive symptoms, rs3804099 showed significant differences in schizophrenia patients with poor concentration in the dominant model (TC/CC vs. TT, p=0.0099). Also, rs3804100 showed a significant association with poor concentration in the co-dominant (TC vs. TT, p=0.014) and the dominant models (TC/CC vs. TT, p=0.0035). We obtained no significant support for the association of the TLR2 gene with susceptibility to schizophrenia in the Korean population. However, our results provide possibility that C allele of rs3804099 and rs3804100 may be associated with poor concentration in schizophrenia patients. Further studies with larger samples are required to confirm our results.