Acknowledgement: the authors thank all volunteers who participated in this study.

Author contribution: Katuntsev VP conceived and designed the study, wrote the manuscript; Sukhostavtseva TV collected and analyzed the obtained data, performed statistical analysis and edited the manuscript; Kotov AN collected and analyzed the obtained data and performed statistical analysis; Baranov MV collected and analyzed the obtained data and edited the manuscript.

Compliance with ethical standards: the study was approved by the Ethics Committee of Federal Research Clinical Center of FMBA (Protocol № 1 dated February 7, 2019) and conformed with the principles of biomedical ethics laid out in the Declaration of Helsinki (the 1964 version and subsequent updates); voluntary informed consent was obtained from each study participant.