Goal: Lithium preparations are considered the most reliable mood stabilizers for patients with Bipolar Disorder (BD), and are the most effective at reducing the risk of suicide. However, maintaining blood lithium concentration within the narrow therapeutic range of 0.4-1.2 mEq is crucial but extremely difficult. The aim of this work is to develop a personal lithium blood level analyzer using a novel method of combined optical and electrical impedance spectroscopy to test micro volumes of spiked samples of human blood.
Results: Impedance measurements alone showed a limit of detection of less than 0.1 mEq within the therapeutic range, whereas optical measurements could verify the presence of lithium and provide a degree of lithium content. Optical specificity to lithium was further verified in qualitative assessment of lithium spiked blood samples with varying concentrations of sodium. Moreover, analysis of multiple linear regression yielded a prediction model of R2 = 0.322716 and RMSEP = 0.223602 for optical measurements only using feature wavelengths, which were found to appear at minima 560 and 605 nm. Combined with impedance measurements, prediction of lithium concentration in samples with unknown lithium content was significantly increased to R2 = 0.876438 and RMSEP = 0.513554.
Conclusion: The combination of optical and impedance modalities for determinations of blood lithium resulted in significant improvement to the sensitivity and accuracy of measurement.
Significance: Results are complementary of the proposed opto-impedance method, and future work will now focus on the technical development of an integrated and miniaturized system for measurement of lithium levels in blood with a high level of accuracy and sensitivity.