1. Wang C, Horby PW, Hayden FG, et al. A novel coronavirus outbreak of global health concern. Lancet 2020; 395(10223): 470-3.
2. Gao Z, Xu Y, Sun C, et al. A systematic review of asymptomatic infections with COVID-19. J Microbiol Immunol Infect 2021; 54(1): 12-6.
3. Chen N, Zhou M, Dong X, et al. Epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: a descriptive study. Lancet 2020; 395(10223): 507-13.
4. Lai CC, Shih TP, Ko WC, et al. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and coronavirus disease-2019 (COVID-19): The epidemic and the challenges. Int J Antimicrob Agents 2020; 55(3): 105924.
5. Lechien JR, Chiesa-Estomba CM, De Siati DR, et al. Olfactory and gustatory dysfunctions as a clinical presentation of mild-to-moderate forms of the coronavirus disease (COVID-19): a multicenter European study. Eur Arch Otorhinolaryngol 2020; 277(8): 2251-61.
6. Cheng L, Li H, Li L, et al. Ferritin in the coronavirus disease 2019 (COVID-19): A systematic review and meta-analysis. J Clin Lab Anal 2020; 34(10): e23618.
7. Vargas-Vargas M, Cortés-Rojo C. Ferritin levels and COVID-19. Rev Panam Salud Publica 2020; 44: e72.
8. Liu F, Li L, Xu M, et al. Prognostic value of interleukin-6, C-reactive protein, and procalcitonin in patients with COVID-19. J Clin Virol 2020; 127: 104370.
9. Tjendra Y, Al Mana AF, Espejo AP, et al. Predicting Disease Severity and Outcome in COVID-19 Patients: A Review of Multiple Biomarkers. Arch Pathol Lab Med 2020; 144(12): 1465-74.
10. Malik P, Patel U, Mehta D, et al. Biomarkers and outcomes of COVID-19 hospitalisations: systematic review and meta-analysis. BMJ Evid Based Med 2021; 26(3): 107-8.
11. Hermans C, Bernard A. Lung epithelium-specific proteins: characteristics and potential applications as markers. Am J Respir Crit Care Med 1999; 159(2): 646-78.
12. Jeon D, Chang EG, McGing M, et al. Pneumoproteins are associated with pulmonary function in HIV-infected persons. PLoS One 2019; 14(10): e0223263.
13. Kirkhus NE, Ulvestad B, Barregard L, et al. Pneumoproteins in Offshore Drill Floor Workers. Int J Environ Res Public Health 2019; 16(3).
14. Moon JY, Leitao Filho FS, Shahangian K, et al. Blood and sputum protein biomarkers for chronic obstructive pulmonary disease (COPD). Expert Rev Proteomics 2018; 15(11): 923-35.
15. Andreeva E, Pokhasnikova M, Lebedev A, et al. Inflammatory parameters and pulmonary biomarkers in smokers with and without chronic obstructive pulmonary disease (COPD). J Thorac Dis 2021; 13(8): 4812-29.
16. Salazar GA, Kuwana M, Wu M, et al. KL-6 But Not CCL-18 Is a Predictor of Early Progression in Systemic Sclerosis-related Interstitial Lung Disease. J Rheumatol 2018; 45(8): 1153-8.
17. Pramana Witarto A, Samarta Witarto B, Er Putra AJ, et al. Serum Krebs von den Lungen-6 for Predicting the Severity of COVID-19 Lung Injury: A Systematic Review and Meta-Analysis. Iran Biomed J 2021; 25(6): 381-9.
18. Naderi N, Rahimzadeh M. Krebs von den Lungen-6 (KL-6) as a clinical marker for severe COVID-19: A systematic review and meta-analyses. Virology 2022; 566: 106-13.
19. Stang A. Critical evaluation of the Newcastle-Ottawa scale for the assessment of the quality of nonrandomized studies in meta-analyses. Eur J Epidemiol 2010; 25(9): 603-5.
20. Higgins JPT, Green S, Cochrane Collaboration, 2008. Cochrane Handbook for Systematic Reviews of Interventions. Cochrane Book Series.Wiley-Blackwell, Chichester, England; Hoboken, NJ.
21. Higgins JP, Thompson SG, Deeks JJ, et al. Measuring inconsistency in meta-analyses. Bmj 2003; 327(7414): 557-60.
22. Schmidt FL, Oh IS, Hayes TL. Fixed- versus random-effects models in meta-analysis: model properties and an empirical comparison of differences in results. Br J Math Stat Psychol 2009; 62(Pt 1): 97-128.
23. Doi SA, Barendregt JJ, Khan S, et al. Advances in the meta-analysis of heterogeneous clinical trials II: The quality effects model. Contemp Clin Trials 2015; 45(Pt A): 123-9.
24. Egger M, Davey Smith G, Schneider M, et al. Bias in meta-analysis detected by a simple, graphical test. Bmj 1997; 315(7109): 629-34
25. Alay H, Laloglu E. The role of angiopoietin-2 and surfactant protein-D levels in SARS-CoV-2-related lung injury: A prospective, observational, cohort study. J Med Virol 2021; 93(10): 6008-15.
26. Awano N, Inomata M, Kuse N, et al. Serum KL-6 level is a useful biomarker for evaluating the severity of coronavirus disease 2019. Respir Investig 2020; 58(6): 440-7.
27. Bergantini L, Bargagli E, d'Alessandro M, et al. Prognostic bioindicators in severe COVID-19 patients. Cytokine 2021; 141: 155455.
28. Chen H, Qin R, Huang Z, et al. Clinical relevance of serum Krebs von den Lungen-6 levels in patients with coronavirus disease 2019. Cytokine 2021; 148: 155513.
29. d'Alessandro M, Cameli P, Refini RM, et al. Serum KL-6 concentrations as a novel biomarker of severe COVID-19. J Med Virol 2020; 92(10): 2216-20.
30. d'Alessandro M, Bergantini L, Cameli P, et al. Peripheral biomarkers' panel for severe COVID-19 patients. J Med Virol 2021; 93(3): 1230-2.
31. Deng K, Fan Q, Yang Y, et al. Prognostic roles of KL-6 in disease severity and lung injury in COVID-19 patients: A longitudinal retrospective analysis. J Med Virol 2021; 93(4): 2505-12.
32. Frix AN, Schoneveld L, Ladang A, et al. Could KL-6 levels in COVID-19 help to predict lung disease? Respir Res 2020; 21(1): 309.
33. Gomes AMC, Farias GB, Dias-Silva M, et al. SARS-CoV2 pneumonia recovery is linked to expansion of innate lymphoid cells type 2 expressing CCR10. Eur J Immunol 2021; 51(12): 3194-201.
34. He L, Lu L, Zong M, et al. The significance of KL-6 as prognosis monitoring biomarker in patients with severe COVID-19 from stabilized stage toward convalescence. 2021.
35. Herr C, Mang S, Mozafari B, et al. Distinct Patterns of Blood Cytokines Beyond a Cytokine Storm Predict Mortality in COVID-19. J Inflamm Res 2021; 14: 4651-67.
36. Kerget B, Kerget F, Koçak AO, et al. Are Serum Interleukin 6 and Surfactant Protein D Levels Associated with the Clinical Course of COVID-19? Lung 2020; 198(5): 777-84.
37. Kerget F, Kerget B, Iba Yilmaz S, et al. Same virus, different course: The relationship between monocyte chemoattractant protein-1 and surfactant protein-a levels and clinical course and prognosis of COVID-19. Flora 2021; 26(3): 410-8.
38. Khadzhieva MB, Gracheva AS, Ershov AV, et al. Biomarkers of air-blood barrier damage in covid-19. Obshchaya Reanimatologiya 2021; 17(3): 16-31.
39. Lim A, Radujkovic A, Weigand MA, et al. Soluble receptor for advanced glycation end products (sRAGE) as a biomarker of COVID-19 disease severity and indicator of the need for mechanical ventilation, ARDS and mortality. Ann Intensive Care 2021; 11(1): 50.
40. Manoppo AF, Veterini AS, Winariani. The correlation between surfactant protein-d (sp-d) serum level and intubation time on covid-19 patients in indonesia. Teikyo Medical Journal 2021; 44(4): 995-1004.
41. Peng DH, Luo Y, Huang LJ, et al. Correlation of Krebs von den Lungen-6 and fibronectin with pulmonary fibrosis in coronavirus disease 2019. Clin Chim Acta 2021; 517: 48-53.
42. Saito A, Kuronuma K, Moniwa K, et al. Serum surfactant protein A and D may be novel biomarkers of COVID-19 pneumonia severity 2020.
43. Scotto R, Pinchera B, Perna F, et al. Serum KL-6 Could Represent a Reliable Indicator of Unfavourable Outcome in Patients with COVID-19 Pneumonia. Int J Environ Res Public Health 2021; 18(4).
44. Shao H, Qin Z, Geng B, et al. Impaired lung regeneration after SARS-CoV-2 infection. Cell Prolif 2020; 53(12): e12927.
45. Spadaro S, Fogagnolo A, Campo G, et al. Markers of endothelial and epithelial pulmonary injury in mechanically ventilated COVID-19 ICU patients. Crit Care 2021; 25(1): 74.
46. Suryananda TD, Yudhawati R. Association of serum KL-6 levels on COVID-19 severity: A cross-sectional study design with purposive sampling. Ann Med Surg (Lond) 2021; 69: 102673.
47. Tong M, Xiong Y, Zhu C, et al. Serum surfactant protein D in COVID-19 is elevated and correlated with disease severity. BMC Infect Dis 2021; 21(1): 737.
48. Wang HY, Chen LC, Zhang Y, et al. Detection of serum KL-6 and SARS-CoV-2 antibody in patients with coronavirus disease 2019 and the diagnostic value in severe disease 2021.
49. Xue M, Zheng P, Bian X, et al. Exploration and correlation analysis of changes in Krebs von den Lungen-6 levels in COVID-19 patients with different types in China. Biosci Trends 2020; 14(4): 290-6.
50. Xue M, Zhang T, Chen H, et al. Krebs Von den Lungen-6 as a predictive indicator for the risk of secondary pulmonary fibrosis and its reversibility in COVID-19 patients. Int J Biol Sci 2021; 17(6): 1565-73.
51. Yalcin Kehribar D, Cihangiroglu M, Sehmen E, et al. The receptor for advanced glycation end product (RAGE) pathway in COVID-19. Biomarkers 2021; 26(2): 114-8.
52. Yamaya T, Hagiwara E, Baba T, et al. Serum Krebs von den Lungen-6 levels are associated with mortality and severity in patients with coronavirus disease 2019. Respir Investig 2021; 59(5): 596-601.
53. Fukuda Y, Homma T, Inoue H, et al. Downregulation of type III interferons in patients with severe COVID-19. J Med Virol 2021; 93(7): 4559-63.
54. Sohrabi C, Alsafi Z, O'Neill N, et al. World Health Organization declares global emergency: A review of the 2019 novel coronavirus (COVID-19). Int J Surg 2020; 76: 71-6.
55. Yao Y, Wang H, Liu Z. Expression of ACE2 in airways: Implication for COVID-19 risk and disease management in patients with chronic inflammatory respiratory diseases. Clin Exp Allergy 2020; 50(12): 1313-24.
56. Calkovska A, Kolomaznik M, Calkovsky V. Alveolar type II cells and pulmonary surfactant in COVID-19 era. Physiol Res 2021; 70(S2): S195-s208.
57. Barreda D, Santiago C, Rodríguez JR, et al. SARS-CoV-2 Spike Protein and Its Receptor Binding Domain Promote a Proinflammatory Activation Profile on Human Dendritic Cells. Cells 2021; 10(12).
58. Kumar A, Narayan RK, Prasoon P, et al. COVID-19 Mechanisms in the Human Body-What We Know So Far. Front Immunol 2021; 12: 693938.
59. Andersen KG, Rambaut A, Lipkin WI. The proximal origin of SARS-CoV-2 Nat Med. 2020; 26(4): 450-2.
60. Hoffmann M, Kleine-Weber H, Schroeder S, et al. SARS-CoV-2 Cell Entry Depends on ACE2 and TMPRSS2 and Is Blocked by a Clinically Proven Protease Inhibitor. Cell 2020; 181(2): 271-80.e8.
61. Li S, Jiang L, Li X, Lin F, Wang Y, Li B, et al. Clinical and pathological investigation of patients with severe COVID-19. JCI Insight 2020; 5(12).
62. Gerosa C, Fanni D, Cau F, et al. Immunohistochemical findings in the lungs of COVID-19 subjects: evidence of surfactant dysregulation. Eur Rev Med Pharmacol Sci 2021; 25(13): 4639-43.
63. Ji Y, Bourke SJ, Spears M, et al. Krebs von den Lungen-6 (KL-6) is a pathophysiological biomarker of early-stage acute hypersensitivity pneumonitis among pigeon fanciers. Clin Exp Allergy 2020; 50(12): 1391-9.
64. Ko UW, Cho EJ, Oh HB, et al. Serum Krebs von den Lungen-6 level predicts disease progression in interstitial lung disease. PLoS One 2020; 15(12): e0244114.
65. Tagami Y, Hara Y, Murohashi K, et al. Comparison of Clinical Features between the High and Low Serum KL-6 Patients with Acute Exacerbation of Interstitial Lung Diseases. Can Respir J 2021; 2021: 9099802.
66. Watson A, Madsen J, Clark HW. SP-A and SP-D: Dual Functioning Immune Molecules With Antiviral and Immunomodulatory Properties. Front Immunol 2020; 11: 622598.
67. Khaket TP, Kang SC, Mukherjee TK. The Potential of Receptor for Advanced Glycation End Products (RAGE) as a Therapeutic Target for Lung Associated Diseases. Curr Drug Targets 2019; 20(6): 679-89.
68. Oczypok EA, Perkins TN, Oury TD. All the "RAGE" in lung disease: The receptor for advanced glycation endproducts (RAGE) is a major mediator of pulmonary inflammatory responses. Paediatr Respir Rev 2017; 23: 40-9.
69. Milne S, Li X, Hernandez Cordero AI, et al. Protective effect of club cell secretory protein (CC-16) on COPD risk and progression: a Mendelian randomisation study. Thorax 2020; 75(11): 934-43.
70. Dickens JA, Lomas DA. CC-16 as a biomarker in chronic obstructive pulmonary disease. Copd 2012; 9(5): 574-5.