Compliance with ethical standards: the study was approved by the Ethics Committee of Ural State Medical University, Federal State Budget Educational Institution of Higher Education under the Ministry of Health of the Russian Federation (Protocol № 7 of September 20, 2019). All patients signed the informed written consent to participation in the study.

Acknowledgments: the authors would like to thank VN Khayutin, director of "Garmonia" Medical Center, for allowing them to conduct the study in the clinic's laboratory department.

Author contribution: Voroshilina ES — organization of the study, data analysis, article authoring; Zornikov DL — data analysis, article authoring; Ivanov AV — statistical processing, data analysis, article authoring; Pochernikov DG — patients’ clinical profile, clinical data collection, data analysis, article authoring; Panacheva EA — literature review, data analysis, conducting PCR tests, article authoring.