A High‐Accuracy and Easy‐Use Differential Diagnosis Method of Bipolar Disorder Depressive Phase and Major Depressive Disorder Using a Wearable Near‐Infrared Spectroscopy

OBJECTIVES: Although conventional multichannel near-infrared spectroscopy (cNIRS) has been reported to be useful in differentiating bipolar disorder depressive phase (BDD) from major depressive disorder (MDD), its utilization in real clinical practice remains limited. The objective of this study was to evaluate the performance of wearable NIRS (wNIRS), which is cheaper to install and easier to use than cNIRS, in differentiating between BDD and MDD, and to propose an optimal index for wNIRS. METHODS: The subjects were 16 BDD patients, 16 MDD patients, and 16 healthy controls. Changes in the total hemoglobin signal (Δ[total-Hb]) in the bilateral frontal cortex during a 60 s verbal fluency task (VFT) were measured using the HOT-2000, a wNIRS capable of reducing noise from skin blood flow. In addition to evaluating the discriminative performance of the integral and centroid values proposed in previous studies, the ratio of the mean values of the Δ[total-Hb] during the first 20 s and subsequent 40 s (20-40 ratio) during the VFT was also employed and assessed. RESULTS: Only the 20-40 ratio showed significant differences between BDD and MDD, whereas the integral and centroid values did not. Using a cut-off value of 2.00 for the 20-40 ratio, the sensitivity and specificity of the BDD diagnosis were 100% and 93.4%, respectively. CONCLUSIONS: The wNIRS measurements and the 20-40 ratio of the Δ[total-Hb] in the forehead area enabled more accurate differentiation between MDD and BDD than the conventional analysis.