Int J Med Sci 2021; 18(1):29-41. doi:10.7150/ijms.49728 This issue

Research Paper

Longitudinal clinical and radiographic evaluation reveals interleukin-6 as an indicator of persistent pulmonary injury in COVID-19

Baolin Liao1,*, Zhipeng Liu2,*, Libo Tang2,*, Linghua Li1,*, Qingxin Gan1,*, Haiyan Shi1, Qian Jiao1, Yujuan Guan1, Min Xie1, Xi He1, Han Zhao1, Weilie Chen1, Yanxia Liu1, Liya Li1, Yaping Wang1, Yi Cao1, Yaling Shi1,#,✉, Yongyin Li2,#,✉, Chunliang Lei1,#,✉

1. Guangzhou Eighth People's Hospital, Guangzhou Medical University, Guangzhou, China
2. Department of Infectious Diseases, Nanfang Hospital, Southern Medical University, Guangzhou, China
* Baolin Liao, Zhipeng Liu, Libo Tang, Linghua Li, and Qingxin Gan are co-first authors
# Yaling Shi, Yongyin Li, and Chunliang Lei contributed equally.

This is an open access article distributed under the terms of the Creative Commons Attribution License ( See for full terms and conditions.
Liao B, Liu Z, Tang L, Li L, Gan Q, Shi H, Jiao Q, Guan Y, Xie M, He X, Zhao H, Chen W, Liu Y, Li L, Wang Y, Cao Y, Shi Y, Li Y, Lei C. Longitudinal clinical and radiographic evaluation reveals interleukin-6 as an indicator of persistent pulmonary injury in COVID-19. Int J Med Sci 2021; 18(1):29-41. doi:10.7150/ijms.49728. Available from

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Graphic abstract

Rationale: Previous studies of coronavirus disease 2019 (COVID-19) were mainly focused on cross-sectional analysis. In this study, we sought to evaluate the dynamic changes of immunological and radiographic features, and the association with the outcome of pulmonary lesions in COVID-19 patients.

Methods: Peripheral blood samples and radiographic data were collected longitudinally for up to 8 weeks from 158 laboratory-confirmed COVID-19 patients. The chest computed tomography (CT) scans were scored based on a semi-quantification assessment according to the extent of pulmonary abnormalities; the temporal change of the immunological and radiographic features was analyzed.

Results: Compared with mild and moderate patients, severe patients had significantly decreased counts of lymphocytes, CD4+ T cells, CD8+ T cells, and CD19+ B cells but dramatically elevated counts of neutrophils and levels of interleukin (IL)-6. Sequential monitoring showed a sustained increase in lymphocytes counts and significantly decreased levels of IL-6 in severe patients during the disease course. Notably, patients with persistent pulmonary lesions (CT score ≥ 5 in week 8) showed high levels of IL-6 during the follow-up period, compared with those with recovery lesions (CT score < 5 in week 8). More importantly, the peak expression of IL-6 prior to the aggravated lung injury was mainly found in patients with persistent lesions, and multivariate analysis showed that IL-6 level upon admission was an independent factor associated with the persistent pulmonary injury.

Conclusion: Prolonged elevation of IL-6 is associated with persistent pulmonary lesions in COVID-19 patients. Sequential monitoring and timely intervention of IL-6 may favor the clinical management of COVID-19.

Keywords: COVID-19, interleukin-6, pulmonary injury, chest CT, sequential monitoring