Background: Bioimpedance has been shown to be a safe technique when used in a number of biomedical applications. In this study, we used the Electro Interstitial Scan (EIS) to perform bioimpedance measurements to follow up the efficacy of selective serotonin reuptake inhibitor (SSRI) treatment in subjects diagnosed to have major depressive disorder.
Methods: We recruited 59 subjects (38 women, 21 men) aged 17-76 (mean 47) years diagnosed with major depressive disorder by psychiatric assessment at the Botkin Hospital according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV). Baseline Clinical Global Impression scores and EIS (electrical conductivity and dispersion α parameter) measurements were done before starting SSRI therapy. Treatment follow-up was undertaken using EIS bioimpedance measurements and by treatment response based on the Hamilton Depression Scale and Clinical Global Impression, every 15 days for 60 days. At day 45, we classified the patients into two groups, ie, Group 1, including treatment responders, and Group 2, including nonresponders. At day 60, patients were classified into two further groups, ie, Group 3, comprising treatment responders, and Group 4, comprising nonresponders.
Results: Comparing Group 1 and Group 2, electrical conductivity measurement of the pathway between the two forehead electrodes had a specificity of 72% and a sensitivity of 85.3% (P < 0.0001), with a cutoff >4.32. Comparing Group 3 and Group 4, electrical conductivity measurements in the same pathway had a specificity of 47.6% and a sensitivity of 76.3% (P < 0.16), with a cutoff >5.92. Comparing Group 1 and Group 2, the electrical dispersion α parameter of the pathway between the two disposable forehead electrodes had a specificity of 80% and a sensitivity of 85.2% (P < 0.0001) with a cutoff >0.678. Comparing Group 3 and Group 4, the electrical dispersion α parameter of the same pathway had a specificity of 100%, a sensitivity of 89.5% (P < 0.0001), and a cutoff >0.692.
Conclusion: Electrical conductivity measurement of the forehead pathway using EIS has a high specificity and sensitivity at day 45 when comparing treatment responders and nonresponders, but decreases at day 60. The EIS electrical dispersion α parameter of the forehead pathway has a high specificity and sensitivity at day 45 when comparing treatment responders and nonresponders, and increases at day 60. The EIS system may be a noninvasive, easily administered, low-cost technique that could be used as an adjunct to DSM-IV and Clinical Global Impression scores for monitoring of efficacy of treatment in patients with major depressive disorder.
Keywords: Electro Interstitial Scan; dispersion α parameter; electrical conductivity; major depressive disorder; selective serotonin reuptake inhibitors.