Russian Journal of Infection and ImmunityRussian Journal of Infection and ImmunityИнфекция и иммунитет2220-76192313-7398SPb RAACI190510.15789/2220-7619-DOM-1905ORIGINAL ARTICLESОРИГИНАЛЬНЫЕ СТАТЬИResearch ArticleDiagnostics of macrophage activation syndrome, depending on IL-6 initial level in patients with a novel coronavirus infectionДиагностика синдрома активации макрофагов в зависимости от исходного уровня IL-6 у пациентов с новой коронавирусной инфекцией, вызванной вирусом SARS-CoV-2https://orcid.org/0000-0002-4535-9805PerepelitsaSvetlana A.ПерепелицаСветлана Александровна
Russian Federation

PhD, MD (Medicine), Associate Professor, Professor of the Department of Surgery, Leading Researcher, Laboratory of Cell Pathology in Critical Conditions, V.A. Negovsky Research Institute of General Reanimatology

д.м.н., доцент, профессор кафедры хирургических дисциплин, ведущий научный сотрудник лаборатории патологии клетки при критических состояниях НИИ общей реаниматологии им. В.А. Неговского

sveta_perepeliza@mail.ruImannuel Kant Baltic Federal UniversityФГАОУ ВО Балтийский федеральный университет имени Иммануила КантаFederal Research and Clinical Center of Intensive Care Medicine and RehabilitologyФГБНУ «Федеральный научно-клинический центр реаниматологии и реабилитологии»17062022151120221246776871803202215052022Copyright ©; 2022, Perepelitsa S.A.Copyright ©; 2022, Перепелица С.А.2022Perepelitsa S.A.Перепелица С.А.https://creativecommons.org/licenses/by/4.0https://iimmun.ru/iimm/article/view/1905

Introduction. The novel coronavirus infection caused by the SARS-CoV-2 remains the main problem, which is being studied by all the efforts of the global scientific community. Large clinical recourse has been accumulated that allows to conduct more effective treatment of patients, but there are still unresolved issues on the pathogenesis for development and course of the disease.

Materials and methods. The study included 163 patients admitted to the infectious diseases hospital diagnosed with “Novel coronavirus infection caused by the SARS-CoV-2”. Upon admission, all patient serum samples were quantified for IL-6 level that allowed to stratify patients into three groups: A — 55 patients with IL-6 below 5.0 pg/ml. The mean age in the group was 57.3±14.9 years, body mass index (BMI) was 28.2±5.6 kg/m2; C — 52 patients whose serum IL-6 level was in the range of 5–49 pg/ml. The average age in the group was 60.8±11.8 years, BMI — 29.6±5.5 kg/m2; C — 56 patients in whom the level of IL-6 in the blood serum ranged within 50–300 pg/ml. The average age in the group was 62.5±15.6 years, BMI — 28.8±5.6 kg/m2. Patients at admission were analysed for serum level of IL-6, IL-8, and C-reactive protein (CRP), ferritin, lactate dehydrogenase (LDH) were also determined on day 3 and 7.

Results. The minimum production of IL-6 within the range of 0.1–5 pg/ml, corresponds to the minimum changes in IL-8, CRP, and ferritin as well as LDH that was within the range of physiological values. Moderate cytokinemia, IL-6 is within the range of 5–49 pg/ml was associated with elevated ferritin and LDH not tending to decline by the end of treatment. Significant cytokinemia, the level of IL-6 within the range of 50–300 pg/ml was associated with hyperferritinemia and increased LDH. The course of COVID-19 in such patients is characterized by increased ferritin by day 3 of treatment, consistently high level of LDH, without a significant trend towards a decline in the studied markers by the end of treatment.

Conclusion. The risk of developing macrophage activation syndrome is not observed of the serum IL-6 level was below 5 pg/ml, whereas ferritin and LDH were within the range of physiological values, with no/degree I ARF. Moderate macrophage activation syndrome is characterized by increased serum IL-6 level within the range 5–49 pg/ml, a moderate increase in LDH and ferritin, as well as signs of ARF I–II degree. Severe signs are diagnosed in case of serum IL-6 level exceeded 50 pg/ml, along with significant increase in LDH and ferritin, as well as signs of II–III degree ARF.

Введение. Новая коронавирусная инфекция, вызванная вирусом SARS-CoV-2, остается главной проблемой, на изучение которой направлены все усилия мирового научного сообщества. Накоплен большой клинический материал, позволяющий более эффективно проводить лечение пациентов, но еще существуют не решенные вопросы патогенеза развития и течения заболевания.

Материалы и методы. В исследование включено 163 пациента, поступивших в инфекционный стационар с установленным диагнозом «Новая коронавирусная инфекция, вызванная вирусом SARS-CoV-2». При поступлении всем больным в сыворотке крови определялся уровень IL-6. В зависимости от его величины проведено разделение на три группы: А — 55 пациентов, у которых в сыворотке крови определялась концентрация IL-6 — менее 5,0 пг/мл. Средний возраст в группе составлял 57,3±14,9 лет, индекс массы тела (ИМТ) — 28,2±5,6 кг/м2; В — 52 пациента, у которых уровень IL-6 в сыворотке крови находился в диапазоне 5–49 пг/мл. Средний возраст в группе составлял 60,8±11,8 лет, ИМТ — 29,6±5,5 кг/м2; С — 56 пациентов, у которых уровень IL-6 в сыворотке крови находился в диапазоне 50–300 пг/мл. Средний возраст в группе составлял 62,5±15,6 лет, ИМТ — 28,8±5,6 кг/м2. Пациентам при поступлении в сыворотке крови определяли IL-6, IL-8, а С-реактивный белок (СРБ), ферритин, лактатдегидрогеназа (ЛДГ) определяли также на 3, 7 сутки.

Результаты. Минимальной продукции IL-6, в диапазоне 0,1–5 пг/мл, соответствуют минимальные изменения IL-8, СРБ, а продукция ферритина и ЛДГ находится в интервале физиологических значений. Умеренная цитокинемия — IL-6 находится в диапазоне 5–49 пг/мл — ассоциирована с повышенным ферритином и ЛДГ без тенденции к снижению к окончанию лечения. Значительная цитокинемия — уровень IL-6 находится в диапазоне 50–300 пг/мл — ассоциирована с гиперферритинемией и повышением ЛДГ. Течение новой коронавирусной инфекции у этих пациентов характеризуется повышением ферритина к 3-м суткам лечения, стабильно высоким уровнем ЛДГ, без существенной тенденции к снижению исследуемых маркеров к окончанию лечения.

Заключение. Риск развития синдрома активации макрофагов отсутствует при уровне IL-6 в сыворотке крови менее 5 пг/мл, ферритин и ЛДГ находятся в диапазоне физиологических значений, ОДН отсутствует или имеются признаки ОДН I степени. Для умеренного синдрома активации макрофагов характерны повышение IL-6 в диапазоне от 5 до 49 пг/мл, умеренное повышение ЛДГ и ферритина, наличие признаков ОДН I–II степени. Выраженные признаки диагностируются при уровне IL-6 в сыворотке крови более 50 пг/мл и сопровождаются значительным повышением ЛДГ и ферритина, признаками ОДН II–III степени.

coronavirusinterleukinsinflammatory responseferritinpneumoniarespiratory failurespleenmicrosplenitisкоронавирусинтерлейкинывоспалительный ответферритинпневмониядыхательная недостаточностьселезенкамикроспленияВозгомент О.В., Пыков М.И., Зайцева Н.В. Новые подходы к ультразвуковой оценке размеров селезенки у детей // Ультразвуковая и функциональная диагностика. 2013. № 6. С. 56–62. [Vozgoment O.V., Pykov M.I., Zaitseva N.V. Ultrasound assessment of spleen size in children. New approaches. Ul’trazvukovaya i funktsional’naya diagnostika = Ultrasound and Functional Diagnostics, 2013, no. 6, pp. 56–62. (In Russ.)]Профилактика, диагностика и лечение новой коронавирусной инфекции (COVID-19). Временные методические рекомендации. Версия 14 (27.12. 2021). 233 с. [Prevention, diagnosis and treatment of novel coronavirus infection (COVID-19). Interim Guidelines. Version 14 (27.12.2021). 233 p. (In Russ.)]Asghar M.S., Haider Kazmi S.J., Khan N.A., Akram M., Hassan M., Rasheed U., Ahmed Khan S. Poor prognostic biochemical markers predicting fatalities caused by COVID-19: a retrospective observational study from a developing country. Cureus., 2020, vol. 12, no. 8: e9575. doi: 10.7759/cureus.9575Batur A., Kılınçer A., Ateş F., Demir N.A., Ergün R. Evaluation of systemic involvement of Coronavirus disease 2019 through spleen; size and texture analysis. Turk. J. Med. Sci., 2021, vol. 51, no. 3, pp. 972–980. doi: 10.3906/sag-2009-270Bohn M.K., Lippi G., Horvath A., Sethi S., Koch D., Ferrari M., Wang C-B., Mancini N., Steele S., Adeli K. Molecular, serological, and biochemical diagnosis and monitoring of COVID-19: IFCC taskforce evaluation of the latest evidence. Clin. Chem. Lab. Med., 2020, vol. 58, no. 7, pp. 1037–1052. doi: 10.1515/cclm-2020-0722Carcillo J.A., Sward K., Halstead E.S., Telford R., Jimenez-Bacardi A., Shakoory B., Simon D., Hall M. A systemic inflammation mortality risk assessment contingency table for severe sepsis. Pediatr. Crit. Care Med., 2016, vol. 18, no. 2, pp. 143–150. doi: 10.1097/PCC.0000000000001029.Caricchio R., Gallucci M., Dass C., Zhang X., Gallucci S., Fleece D., Bromberg M., Criner G.J. Preliminary predictive criteria for COVID-19 cytokine storm. Ann. Rheum. Dis., 2021, vol. 80, no. 1, pp. 88–95. doi: 10.1136/annrheumdis-2020-218323Cazzola M., Bergamaschi G., Tonon L., Arbustini E., Grasso M., Vercesi E., Barosi G., Bianchi P.E., Cairo G., Arosio P. Hereditary hyperferritinemia-cataract syndrome: relationship between phenotypes and specific mutations in the iron-responsive element of ferritin light-chain mRNA. Blood, 1997, no. 90, p.814.Chen G., Wu D., Guo W., Cao Y., Huang D., Wang H., Wang T., Zhang X., Chen H., Yu H., Zhang X., Zhang M., Wu S., Song J., Chen T., Han M., Li S., Luo X., Zhao J., Ning Q. Clinical and immunological features of severe and moderate coronavirus disease 2019. J. Clin. Invest., 2020, vol. 130, no. 5, pp. 2620–2629. doi: 10.1172/JCI137244Chen Y., Klein S.L., Garibaldi B.T., Li H., Wu C., Osevala N.M., Li T., Margolick J.B., Pawelec G., Leng S.X. Aging in COVID-19: Vulnerability, immunity and intervention. Ageing Res. Rev., 2021, no. 65: 101205. doi: 10.1016/j.arr.2020.101205Cohen L.A., Gutierrez L., Weiss A., Leichtmann-Bardoogo Y., De-liang Zhang, Crooks D.R., Sougrat R., Morgenstern A., Galy B., Hentze M.W., Lazaro F.J., Rouault T.A., Meyron-Holtz E.G. Serum ferritin is derived primarily from macrophages through a nonclassical secretory pathway. Blood, 2010, vol. 116, no. 9, pp. 1574-1584. doi: 10.1182/blood-2009-11-253815Coster D., Wasserman A., Fisher E., Rogowski O., Zeltser D., Shapira I., Bernstein D., Meilik A., Raykhshtat E., Halpern P., Berliner S., Tsarfaty S.S., Shamir R. Using the kinetics of C-reactive protein response to improve the differential diagnosis between acute bacterial and viral infections. Infection, 2020, no. 48, pp. 241–248. doi: 10.1007/s15010-019-01383-6.Eklund C.M. Proinflammatory cytokines in CRP baseline regulation. Adv. Clin. Chem., 2009, no. 48, pp. 111–136. doi: 10.1016/s0065-2423(09)48005-3Gu J., Gong E., Zhang B., Zheng J., Gao Z., Zhong Y., Zou W., Zhan J., Wang S., Xie Z., Zhuang H., Wu B., Zhong H., Shao H., Fang W., Gao D., Pei F., Li X., He Z., Xu D., Shi X., Anderson V.M., Leong A.S.-Y. Multiple organ infection and the pathogenesis of SARS. J. Exp. Med., 2005, vol. 202, no. 3, pp. 415–424. doi: 10.1084/jem.20050828Guan W.J., Ni Z.Y., Hu Y., Liang W.H., Ou C.Q., He J.X., Liu L., Shan H., Lei C.L., Hui D.S.C., Du B., Li L.J., Zeng G., Yuen K.Y., Chen R.C., Tang C.L., Wang T., Chen P.Y., Xiang J., Li S.Y., Wang J.L., Liang Z.J., Peng Y.X., Wei L., Liu Y., Hu Y.H., Peng P., Wang J.M., Liu J.Y., Chen Z., Li G., Zheng Z.J., Qiu S.Q., Luo J., Ye C.J., Zhu S.Y., Zhong N.S. Clinical characteristics of Coronavirus Disease 2019 in China. N. Engl. J. Med., 2020, vol. 382, no. 18, pp. 1708–1720. doi: 10.1056/NEJMoa2002032Gubernatorova E.O., Gorshkova E.A., Polinova A.I., Drutskaya M.S. IL-6: relevance for immunopathology of SARS-CoV-2. Cytokine Growth Factor Rev., 2020, no. 53, pp. 13–24. doi: 10.1016/j.cytogfr.2020.05.009Henry B.M., de Oliveira M.H., Benoit S., Plebani M., Lippi G. Hematologic, biochemical and immune biomarker abnormalities associated with severe illness and mortality in coronavirus disease 2019 (COVID-19): a meta-analysis. Clin. Chem. Lab. Med., 2020. vol. 58 no. 7, pp. 1021–1028. doi: 10.1515/cclm-2020-0369Honore P.M., Gutierrez B. L, Kugener L., Redant S., Attou R., Gallerani A., De Bels D. Inhibiting IL-6 in COVID-19: we are not sure. Crit. Care, 2020, vol. 24, no. 1: 463. doi: 10.1186/s13054-020-03177-xKang S., Tanaka T., Narazaki M., Kishimoto T. Targeting interleukin-6 signaling in clinic. Immunity, 2019, vol. 50, no. 4, pp. 1007–1023. doi: 10.1016/j.immuni.2019.03.026Kernan K.F., Carcillo J.A. Hyperferritinemia and inflammation. Int. Immunol., 2017, vol. 29, no. 9, pp 401–409. doi: 10.1093/intimm/dxx031Li X., Xu S., Yu M., Wang K., Tao Y., Zhou Y., Shi J., Zhou M., Wu B., Yang Z., Zhang C., Yue J., Zhang Z., Renz H., Liu X., Xie J., Xie M., Zhao J. Risk factors for severity and mortality in adult COVID-19 inpatients in Wuhan. J. Allergy Clin. Immunol., 2020, vol. 146, no. 1, pp. 110–118. doi: 10.1016/j.jaci.2020.04.006Lippi G., Plebani M. Laboratory abnormalities in patients with COVID-2019 infection. Clin. Chem. Lab. Med., 2020, vol. 58, no. 7, pp. 1131–1134. doi: 10.1515/cclm-2020-0198Liu Y., Yang Y., Zhang C., Huang F., Wang F., Yuan J., Wang Z., Li J., Li J., Feng C., Zhang Z., Wang L., Peng L., Chen L., Qin Y., Zhao D., Tan S., Yin L., Xu J., Zhou C., Jiang C., Liu L. Clinical and biochemical indexes from 2019-nCoV infected patients linked to viral loads and lung injury. Sci. China Life Sci., 2020, vol. 63, no. 3, pp. 364–374. doi: 10.1007/s11427-020-1643-8Lubell Y., Blacksell S.D., Dunachie S., Tanganuchitcharnchai A., Althaus T., Watthanaworawit W., Paris D.H., Mayxay M., Peto T.J., Dondorp A.M., White N.J., Day N.P.J., Nosten F., Newton P.N., Turner P. Performance of Creactive protein and procalcitonin to distinguish viral from bacterial and malarial causes of fever in Southeast Asia. BMC Infect. Dis., 2015, no. 15: 511. doi: 10.1186/s12879-015-1272-6Machhi J., Herskovitz J., Senan A.M., Dutta D., Nath B., Oleynikov M.D., Blomberg W.R., Meigs D.D., Hasan M., Patel M., Kline P., Chang R.C., Chang L., Gendelman H.E., Kevadiya B.D. The natural history, pathobiology, and clinical manifestations of SARS-CoV-2 infections. J. Neuroimmune Pharmacol., 2020, vol. 15, no. 3, pp. 359–386. doi: 10.1007/s11481-020-09944-5Maeda T., Obata R., Rizk D.D., Kuno T. The Association of interleukin-6 value, interleukin inhibitors and outcomes of patients with COVID-19 in New York City. J. Med. Virol., 2021, vol. 93, no. 1, pp. 463-471. doi: 10.1002/jmv.26365Martinez-Outschoorn U.E., Prisco M., Ertel A. Ketones and lactate increase cancer cell “stemness,” driving recurrence, metastasis and poor clinical outcome in breast cancer: achieving personalized medicine via metabolo-genomics. Cell. Cycle, 2011, vol. 10, no. 8, pp. 1271–1286. doi: 10.4161/cc.10.8.15330.McFadyen J., Kiefer J., Loseff-Silver J., Braig D., Potempa L.A., Eisenhardt S.U., Peter K. Dissociation of C-reactive protein localizes and amplifies inflammation: Evidence for a direct biological role of CRP and its conformational changes. Front. Immunol., 2018, no. 9: 1351. doi: 10.3389/fimmu.2018.01351Mehta P., McAuley D.F., Brown M., Sanchez E., Tattersall R.S., Manson J.J. COVID-19: consider cytokine storm syndromes and immunosuppression. Lancet, 2020, vol. 395, no. 10229, pp. 1033–1034. doi: 10.1016/S0140-6736(20)30628-0Onur S.T., Altın S., Sokucu S.N., Fikri B.İ., Barça T., Bolat E., Toptaş M. Could ferritin level be an indicator of COVID-19 disease mortality? J. Med. Virol., 2021, vol. 93, no. 3, pp. 1672–1677. doi: 10.1002/jmv.26543Rajab I.M., Hart P.C., Potempa L.A. How C-reactive protein structural isoforms with distinctive bioactivities affect disease progression. Front. Immunol., 2020, no. 11: 2126. doi: 10.3389/fimmu.2020.02126Ramasamy S., Subbian S. Critical determinants of cytokine storm and type i interferon response in COVID-19 pathogenesis. Clin. Microbiol. Rev., 2021, vol. 34, no. 3: e00299-20. doi: 10.1128/CMR.00299-20Recalcati S., Invernizzi P., Arosio P., Cairo G. New functions for an iron storage protein: the role of ferritin in immunity and autoimmunity. J. Autoimmun., 2008. vol. 30, no. 1–2, pp. 84–89. doi: 10.1016/j.jaut.2007.11.003Sette А., Crotty S. Adaptive immunity to SARS-CoV-2 and COVID-19. Cell, 2021, vol. 184, no. 4, pp. 861–880. doi: 10.1016/ j.cell.2021.01.007Shrive A.K., Cheetham G.M.T., Holden D., Myles D.A.A., Turnell W.G., Volanakis J.E., Pepys M.B., Bloomer A.C., Greenhough T.J. Three-dimensional structure of human C-reactive protein. Nat. Struct. Biol., 1996, vol. 3, no. 4, pp. 346–354. doi: 10.1038/nsb0496-346Solis-Garcia Del Pozo J., Galindo M.F., Nava E., Jordan J. A systematic review on the efficacy and safety of IL-6 modulatory drugs in the treatment of COVID-19 patients. Eur. Rev. Med. Pharmacol. Sci., 2020, vol. 24, no. 13, pp. 7475–7484. doi: 10.26355/eurrev_202007_21916Soy M., Keser G., Atagündüz P., Tabak F., Atagündüz I., Kayhan S. Cytokine storm in COVID-19: pathogenesis and overview of anti-inflammatory agents used in treatment. Clin. Rheumatol., 2020, vol. 39, no. 7, pp. 2085–2094. doi: 10.1007/s10067-020-05190-5Tonial C.T., Garcia P.C.R., Schweitzer L.C., Costa C.A.D., Bruno F., Fiori H.H., Einloft P.R., Garcia R.B., Piva J.P. Cardiac dysfunction at echocardiogram and ferritin as early markers of severity in pediatric sepsis. J. Pediatr. (Rio J.), 2017, vol. 93, no. 3, pp. 301–307. doi: 10.1016/j.jped.2016.08.006Vigushin D.M., Pepys M.B., Hawkins P.N. Metabolic and scintigraphic studies of radioiodinated human C-reactive protein in health and disease. J. Clin. Invest., 1993, vol. 91, no. 4, pp. 1351–1357. doi: 10.1172/JCI116336Wang G., Wu C., Zhang Q., Wu F., Yu B., Lv J., Li Y., Li T., Zhang S., Wu C., Wu G., Zhong Y. C reactive protein level may predict the risk of COVID-19 aggravation. Open Forum Infect. Dis., 2020, vol. 7, no. 5: ofaa153. doi: 10.1093/ofid/ofaa153Wang L. C-reactive protein levels in the early stage of COVID-19. Med. Maladies Infect., 2020, vol. 50, no. 4, pp. 332–334. doi: 10.1016/j.medmal.2020.03.007Weatherhead J.E., Clark E.H., Vogel T.P., Atmar R.L., Kulkarni P.A. Inflammatory syndromes associated with SARS-CoV-2 infection: dysregulation of the immune response across the age spectrum. J. Clin. Invest., 2020, vol. 130, no. 12, pp. 6194–6197. doi: 10.1172/JCI145301.Wu Y., Potempa L.A., Kebir D.E., Filep J.G. C-reactive protein and inflammation: conformational changes affect function. Biol. Chem., 2015, vol. 396, no. 11, pp. 1181–1197. doi: 10.1515/hsz-2015-0149Xu X., Chang X.N., Pan H.X., Su H., Huang B., Yang M., Luo D.J., Weng M.X., Ma L., Nie X. Pathological changes of the spleen in ten patients with coronavirus disease 2019(COVID-19) by postmortem needle autopsy. Zhonghua Bing Li Xue Za Zhi., 2020, vol. 49, no. 6, pp. 576–582. doi: 10.3760/cma.j.cn112151-20200401-00278Xu Z., Shi L., Wang Y., Zhang J., Huang L., Zhang C., Liu S., Zhao P., Liu H., Zhu L., Tai Y., Bai C., Gao T., Song J., XiaP., Dong J., Zhao J., Wang F.-S. Pathological findings of COVID-19 associated with acute respiratory distress syndrome. Lancet Respir. Med., 2020, vol. 8, no. 4, pp. 420–422. doi: 10.1016/S2213-2600(20)30076-XYang X., Yu Y., Xu J., Shu H., Xia J., Liu H., Wu Y., Zhang L., Yu Z., Fang M., Yu T., Wang Y., Pan S., Zou X., Yuan S., Shang Y. Clinical course and outcomes of critically ill patients with SARS-CoV-2 pneumonia in Wuhan, China: a single-centered, retrospective, observational study. Lancet Respir. Med., 2020, vol. 8, no. 5, pp. 475–481. doi: 10.1016/S2213-2600(20)30079-5Yao X., Li T., He Z., Ping Y., Liu H., Yu S., Mou H., Wang L., Zhang H., Fu W., Luo T., Liu F., Guo Q.N., Chen C., Xiao H.L., Guo H.T., Lin S., Xiang D.F., Shi Y., Pan G.Q., Li Q.R., Huang X., Cui Y., Liu X.Z., Tang W., Pan P.F., Huang X.Q., Ding Y.Q., Bian X.W. A pathological report of three COVID-19 cases. Zhonghua Bing Li Xue Za Zhi., 2020, vol. 49, no. 5, pp. 411–417. doi: 10.3760/cma.j.cn112151-20200312-00193Yi K., Rong Y., Wang C., Huang L., Wang F. COVID-19: advance in laboratory diagnostic strategy and technology. Mol. Cell Biochem., 2021, vol. 476, no. 3, pp. 1421–1438. doi: 10.1007/s11010-020-04004-1Zhang T., Chen H., Liang S., Chen D., Zheng C., Zeng C., Zhang H., Liu Z. A non-invasive laboratory panel as a diagnostic and prognostic biomarker for thrombotic microangiopathy: development and application in a Chinese cohort study. PLoS One, 2014, vol. 9, no. 11: e111992. doi: 10.1371/journal.pone.0111992Zhou F., Yu T., Du R., Fan G., Liu Y., Liu Z., Xiang J., Wang Y., Song B., Gu X., Guan L., Wei Y., Li H., Wu X., Xu J., Tu S., Zhang Y., Chen H., Cao B. Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: a retrospective cohort study. Lancet, 2020, vol. 395, no. 10229, pp. 1054–1062. doi: 10.1016/S0140-6736(20)30566-3