Routine Biochemical Indices:
Different biochemical indices are summarized in Table 1, which shows an insignificant increase in WBC count in patients. In contrast, the % lymphocyte count and % granulocytes were significantly increased in patients with p<0.001 and p<0.05, respectively, compared to the control group. The occurrence of dyslipidemia observed in schizophrenic patients suggests high levels of Plasma total lipid (P<0.048), total cholesterol(P<0.046), triglycerides (P>0.033), and low levels of HDL cholesterol (P>0.033).
Inflammatory Markers:
ELISA-based analysis of serum inflammatory markers measurement (IFN-γ, TNF-α, IL-1α, GM-CSF, and hs-CRP) depicts a significant decrease in the level of IFN-γ (P<0.003) and TNF-α (P<0.017) in schizophrenic patients. Contrary to no significant differences were observed in IL-1α and GM-CSF levels compared to controls. Additionally, the hs-CRP level was significantly (P>0.033) increased in patients compared to the control group.
Table 1: Comparative profile of Biochemical Indices in Schizophrenia patients compared to healthy controls.
Indices/ Profiles
|
Biochemical Parameters
|
Control (n=50)
Mean ±SD
|
Schizophrenic Patients(n=50)
Mean ±SD
|
P-Value
|
WBCs Profile
|
WBC (103/mL)
|
7.45 ± 1.73
|
7.88 ± 2.68
|
N.S.
|
%Lymphocytes
|
30.30 ± 6.18
|
33.24 ±4.70**
|
<0.002 **
|
%Granulocytes
|
58.18 ± 7.99
|
62.04 ± 7.04*
|
<0.033 *
|
%Monocytes
|
4.98 ± 2.12
|
4.73 ± 0.86
|
N.S.
|
Lipid Profile
|
Total Lipid (mg/dl)
|
287.3±44.03
|
324.3±86.1
|
0.048*
|
Total Cholesterol (mg/dl)
|
129.6±24.18
|
140.4±42.15
|
0.046*
|
Triglyceride (mg/dl)
|
105.7±26.61
|
124.6±55.52
|
<0.033 *
|
HDL-Cholesterol (mg/dl)
|
61.81±19.22
|
48.33±36.01
|
<0.033 *
|
LDL-Cholesterol (mg/dl)
|
87.31±34.06
|
90.34±36.85
|
NS
|
Hs-CRP
|
Hs-CRP
|
1.67±0.256
|
1.83±0.223
|
<0.033 *
|
Inflammatory Markers
|
IL 1α
|
6.851±4.72
|
6.24±7.00
|
NS
|
IFN γ
|
33.00±7.076
|
22.29±6.574
|
0.002**
|
TNF
|
29.70±25.55
|
15.84±10.60
|
0.033*
|
GM-CSF
|
5.385±2.27
|
5.381±3.116
|
NS
|
Level of significance ***p<0.0001, **p<0.01, *p<0.05 as compared with control (t-test)
Oxidative stress Markers:
The C- Statistics analysis reveals that the mean±S.D. of PON1, TOS, and TAS values were significantly low (Figure 1), while OSI values were significantly high in schizophrenic patients compared to the control group. The optimal cut-off levels and associated diagnostic performances (sensitivity, specificity) of PON1, TOS, TAS, and OSI, based on ROC analysis, are shown in Figure 2.
The analysis revealed a high diagnostic value for TOS and OSI in schizophrenic patients, with an area under the curve (AUC) of 0.564 and 0.620, respectively. On the other hand, the diagnostic values for TAS and PON1 were higher in controls, with AUCs of 0.607 and 0.731, respectively (Table 2).
The data were statistically analyzed using a paired t-test to compare two mean populations (TOS with TAS and OSI with PON1) and ANOVA to analyze differences among group means that show no significant differences among these stress markers. In addition, Levene's test was used to test the equality of variances, similar to ANOVA. The absolute value depicts the dependent variable calculated by the difference between a score and the mean of the associated group.
The test statistic W equals the F-statistic generated as an ANOVA (p>.05). As the p-value is above 0.05, the null hypothesis according to which the groups have equal variance except for TOS*(P<0.001) concluded that there is a statistically significant difference between the variance.
Pearson's correlation analysis
Table 3 revealed various correlations among different data sets using Pearson's correlation analysis. A significant positive correlation existed between oxidative stress index-OSI with total oxidant status-TOS (r = 0.825**, p>0.01) and a significant negative correlation with total antioxidant status-TAOC/TAS (r = -0.325**, p>0.01). However, these markers did not significantly correlate with other indices such as lipid profile, S-100B, PON1, CRP, inflammatory markers, and WBCs indices.
Total Lipid is positively correlated with triglyceride (r=0.835**), total Cholesterol (r=0.549**), and LDL (r=0.448**). Moreover, LDL showed a significant correlation with total Cholesterol and triglyceride. The WBCs indices in schizophrenic patients showed no significant correlation except with lymphocytes, a significant positive correlation with monocytes, and a negative correlation with granulocytes.
Table 2: AUC Values of Different Oxidative Stress Markers in Schizophrenic Patients and Healthy Controls.
Markers
|
Control
|
Patients
|
ANOVA
(Combined)
|
F
|
Significance
|
Levene's Test for Equality of Variances
|
F
|
Significance
|
TOS
|
0.436
|
0.564
|
Between Groups
|
.481
|
.490
|
Equal variances assumed
Equal variances not assumed
|
12.602
|
.001*
|
Within Groups
|
Total
|
TAS
|
0.607
|
0.393
|
Between Groups
|
1.777
|
.187
|
Equal variances assumed
Equal variances not assumed
|
.468
|
.496
|
Within Groups
|
Total
|
OSI
|
0.380
|
0.620
|
Between Groups
|
.496
|
.484
|
Equal variances assumed
Equal variances not assumed
|
.998
|
.321
|
Within Groups
|
Total
|
PON1
|
0.731
|
0.269
|
Between Groups
|
1.692
|
.197
|
Equal variances assumed
Equal variances not assumed
|
.209
|
.648
|
Within Groups
|
Total
|
*Except for TOS, there are no significant results in the independent sample test. Levene's test verified the equality of variances in all the samples (homogeneity of variance) (p>.05). As the p-value is above 0.05, the null hypothesis means all the groups have equal variance except TOS*depicts that the difference between the variances is significant.
Table 3: Pearson Correlation of Different Biomarkers in Schizophrenic Patients and Healthy Controls.
Markers
|
Control
|
Patients
|
ANOVA
(Combined)
|
F
|
Significance
|
Levene's Test for Equality of Variances
|
F
|
Significance
|
TOS
|
0.436
|
0.564
|
Between Groups
|
.481
|
.490
|
Equal variances assumed
Equal variances not assumed
|
12.602
|
.001*
|
Within Groups
|
Total
|
TAS
|
0.607
|
0.393
|
Between Groups
|
1.777
|
.187
|
Equal variances assumed
Equal variances not assumed
|
.468
|
.496
|
Within Groups
|
Total
|
OSI
|
0.380
|
0.620
|
Between Groups
|
.496
|
.484
|
Equal variances assumed
Equal variances not assumed
|
.998
|
.321
|
Within Groups
|
Total
|
PON1
|
0.731
|
0.269
|
Between Groups
|
1.692
|
.197
|
Equal variances assumed
Equal variances not assumed
|
.209
|
.648
|
Within Groups
|
Total
|
** Correlation is significant at the 0.01 level (2-tailed),
* Correlation is significant at the 0.05 level (2-tailed
OSI Correlation Interactive graph
In automatic linear modeling, the thicknesses are demonstrated in an interactive graph corresponding to the predictive power of a predictor line showing its predictability value for the dependent variable. The histogram shows the results with its best-fitted Gaussian curve [20]. The correlation analysis revealed that a significant correlation existed between Oxidative stress index-OSI with Total oxidant status-TOS (r = 0.825**, p>0.01) and Total Antioxidant status-TAOC/TAS (r = -0.325**, p>0.01). A significant positive correlation with TOS was observed, while a negative correlation was observed with TAOC/TAS. While the least significant correlation with lymphocytes, granulocytes, and an inflammatory marker, TNF (Figure 3), may suggest that oxidative stress is involved in Schizophrenia.