CURRENT STATUS AND PROBLEMS OF NEUROIMAGING-GUIDED DIAGNOSIS USING NEAR-INFRARED SPECTROSCOPY IN JAPAN

Abstract Background Near-infrared spectroscopy (NIRS) has been approved as an insurance-covered auxiliary laboratory test for differential diagnosis of depressive state in Japan. However, reports indicated a certain mismatching rate between psychiatric diagnosis and NIRS waveform pattern, which may be due to age-related decline in cortical activity, various clinical stages, dose-dependent impact of psychotropic drugs, and individual biological conditions on NIRS signals. Aim To investigate the relationship between patient-related factors such as basic characteristics, current psychiatric medication, and blood tests and prefrontal hemodynamic responses around the same time, and the difference of these factors against NIRS classification in psychiatric subjects. Methods The subjects comprised 118 with bipolar disorder (BD), 123 with major depressive disorder (MD), and 45 schizophrenia/schizoaffective disorder (SZ). Using a 22-channel optical topography system, changes in the concentration of oxygenated hemoglobin in prefrontal cortices were measured during a verbal fluency test. The data were retrospectively analyzed to see any significant correlation between age, disease duration, Global Assessment of Functioning (GAF) scores, chlorpromazine equivalents (CPeq) levels, imipramine equivalents (IMPeq) levels;, benzodiazepine equivalents (DZPeq) levels, white blood cell (WBC) counts, red blood cell (RBC) counts, platelet (Plt) counts, serum sodium (S-Na) levels, serum potassium levels, and serum fasting blood sugar levels, and NIRS indices (integral value: AUC, centroid value: Balance, and initial value: Axis), which were divided by cortex region (fontal: F and temporal: T) and psychiatric disease. In addition, they were compared between coincidence (positive) subjects and non-coincidence (negative) subjects against corresponding NIRS classification within psychiatric disease. The ethics committee of Kusatsu Hospital approved this study, and informed consent to analyze the stacked data was obtained from all subjects. Results 1) In BD subjects, age and disease duration were negatively correlated with F-AUC and T-AUC; IMPeq levels were negatively correlated with F-AUC, F-Balance, T- AUC and T-Balance; WBC counts were positively correlated with T-Axis; S-Na levels were positively correlated with F-AUC and T-AUC. In MD subjects, GAF scores were positively correlated with F-Axis; S- Na levels were positively correlated with F-Balance. In SZ subjects, RBC counts were positively correlated with T-AUC, F-Balance and T-Balance; Plt counts were negatively correlated with T-AUC and T-Axis; S-Na levels were positively correlated with F-Balance. 2) S-Na levels in BD-negative 66 subjects were significantly lower than those in BD-positive 52 subjects. IMPeq levels in MD-negative 76 subjects were significantly higher than those in MD-positive 47 subjects. GAF levels in SZ-negative 19 subjects were significantly higher than those in SZ-positive 26 subjects. Conclusion A single-center and cross- sectional observational method, and a lack of control subjects were limitations in this study, however, disease duration, IMPeq levels, blood cells counts, and serum sodium levels were related to NIRS waveform pattern in psychiatric subjects. Furthermore, state of mental disturbance, dose of antidepressant, and serum electrolytes should be taken into account when NIRS signals are utilized for differential diagnosis of psychiatric disorders.