Author contribution: Kravets VI, Posadskaya AV, Krasnov NM — study concept and design; Shen PA, Gureshidze MA, Krasnov NM — patient follow-up and data processing; Zhitareva IV — statistical processing; Krasnov NM — manuscript draft writing; Poryadin GV, Eremin DA, Khelminskaya NM — editing.

Compliance with ethical standards: the study was approved by the Ethics Committee of the Pirogov Russian National Research Medical University (protocol № 131 of 27 January 2014), the patients submitted the informed consent to study participation.