How to design a reliable and practical biomarker: the electrophysiologic coefficient of depressiveness - δEPCD

This letter to editor contains an overview of commentary article in which the authors explain how they designed the novel biomarker. The Electrophysiologic Coefficient of Depressiveness - δEPCD detects the presence of a depressive disorder while being able to quantify its severity. This biomarker follows vital function - high frequency heart rate variability in relation with neuroactive metabolic components - concentration ratio between quinolinic acid, and kynurenine acid and it is both sensitive and specific in regard to depressive disorders. Diagnostics of depressive disorders could be improved by checking this novel biomarker and/or re-assessment of individuals who might have depression as well as in rising the awareness about the depressive disorders' prevalence and treatment. So far biomarkers have been classified as dynamic (descriptive) or static (prognostic). With this new complex biomarker, that comprises potentials of both categories, we might be able to introduce a new category - a physiological biomarker. Physiological biomarkers should not have exclusive application within the depressive disorder, but the future research should identify more physiological biomarkers related to other diseases.However, the findings need further evidence procuring new information regarding diagnostics of depressive disorders. Though it presents a novel methodology which would add to a biomarkers research, more specifically type-classification, lack of clear and concise protocol regarding clinical interpretation and a consistent administrative structure and/or logistics to perform the measurements are present. For this reason, further research in different settings and on a larger sample size are necessary.