Clinical significance of serum IgM and IgG levels in COVID-19 patients in Hubei Province, China

Zhenjiang Bai; Qing Li; Qinghui Chen; Changming Niu; Yu Wei; Hanpeng Huang; Wei Zhao; Nian Chen; Xin Yao; Qiang Zhang; Chuanyong Mu; Jian Feng; Chuanlong Zhu; Zhuo Li; Ming Ding; Binhui Feng; Chaochao Jin; Xiang Lu; Yi Yang; Shuiyan Wu; Xiaochen Shu; Lifang Hu; Haibo Qiu; YingZi Huang

doi:10.1016/j.jointm.2021.09.001

Clinical significance of serum IgM and IgG levels in COVID-19 patients in Hubei Province, China

J Intensive Med. 2021 Oct 4;2(1):32-38. doi: 10.1016/j.jointm.2021.09.001. eCollection 2022 Jan.

Authors

Zhenjiang Bai¹, Qing Li², Qinghui Chen³, Changming Niu⁴, Yu Wei⁵, Hanpeng Huang⁶, Wei Zhao⁷, Nian Chen⁸, Xin Yao⁹, Qiang Zhang¹⁰, Chuanyong Mu¹¹, Jian Feng¹², Chuanlong Zhu⁸, Zhuo Li¹³, Ming Ding¹⁰, Binhui Feng¹⁴, Chaochao Jin¹⁵, Xiang Lu¹⁶, Yi Yang², Shuiyan Wu¹, Xiaochen Shu¹⁷, Lifang Hu¹⁸, Haibo Qiu², YingZi Huang²

Affiliations

¹ Pediatric Intensive Care Unit, Children's Hospital of Soochow University, Suzhou, Jiangsu 215025, China.
² Department of Critical Care Medicine, Zhongda Hospital, School of Medicine, Southeast University, Nanjing, Jiangsu 210009, China.
³ Department of Infectious Diseases, Children's Hospital of Soochow University, Suzhou, Jiangsu 215025, China.
⁴ Department of Critical Care Medicine, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210011, China.
⁵ Department of Respirology, Jiangsu Province Hospital of TCM, Nanjing, Jiangsu 210046, China.
⁶ Department of Respirology, Affiliated Hospital of Jiangsu University, Zhenjiang, Jiangsu 212001, China.
⁷ Department of Critical Care Medicine, Sir Run Hospital Nanjing Medical University, Nanjing, Jiangsu 211112, China.
⁸ Department of Infectious Diseases, The Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 211103, China.
⁹ Department of Respiratory and Critical Care Medicine, The Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 211103, China.
¹⁰ Department of Respirology, Southeast University Zhongda Hospital, Nanjing, Jiangsu 210009, China.
¹¹ Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215006, China.
¹² Department of Respiratory and Critical Care Medicine, Affiliated Hospital of Nantong University, Nantong, Jiangsu 226019, China.
¹³ Department of Emergency, Children's Hospital of Nanjing Medical University, Nanjing, Jiangsu 210008, China.
¹⁴ Department of Critical Care Medicine, Huangshi Central Hospital, Huangshi, Hubei 435002, China.
¹⁵ Department of Oncology, Huangshi Hospital of TCM (Infectious Disease Hospital, Huangshi, Hubei 435002, China.
¹⁶ Department of Geriatric Medicine, Sir Run Hospital Nanjing Medical University, Nanjing, Jiangsu 211112, China.
¹⁷ Department of Epidemiology, School of Public Health, Medical College of Soochow University, Suzhou, Jiangsu 215031, China.
¹⁸ Jiangsu Key Laboratory of Neuropsychiatric Diseases and Institute of Neuroscience, Soochow University, Suzhou, Jiangsu 215031, China.

Abstract

Background: There have been many studies about coronavirus disease 2019 (COVID-19), but the clinical significance of quantitative serum severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2)-specific IgM and IgG levels of COVID-19 patients have not been exhaustively analyzed. We aimed to investigate the time profiles of these IgM/IgG levels in COVID-19 patients and their correlations with clinical features.

Methods: A multicenter clinical study was conducted from February 20 to March 5 2020. It involved 179 COVID-19 patients (108 males and 71 females) from five hospitals in Huangshi in Hubei Province, China. To detect SARS-CoV-2-specific IgM/IgG, quantitative antibody assays (two-step indirect immunoassays with direct chemiluminescence technology) based on the nucleocapsid protein (NP) and spike protein 1 (S1) were used. For normally distributed data, means were compared using the t-test, χ ²-test, or exact probability method. For categorical data, medians were compared using Mann-Whitney U test.

Results: The median age was 57 (44-69) years (58 [38-69] for males and 57 [49-68] for females). The median duration of positive nucleic acid test was 22.32 (17.34-27.43) days. The mortality rate was relatively low (3/179, 1.68%). Serum SARS-CoV-2-specific IgG was detected around week 1 after illness onset, gradually increased until peaking in weeks 4 and 5, and then declined. Serum IgM peaked in weeks 2 and 3, then gradually declined and returned to its normal range by week 7 in all patients. Notably, children had milder respiratory symptoms with lower SARS-CoV-2-specific IgM/IgG levels. The duration of positive nucleic acid test in the chronic obstructive pulmonary disease (COPD) group was 30.36 (18.99-34.76) days, which was significantly longer than that in the non-COPD group (21.52 [16.75-26.51] days; P = 0.025). The peak serum SARS-CoV-2-specific IgG was significantly positively correlated with the duration of positive nucleic acid test. The incidence rate of severe and critical cases in the IgM^hi group (using the median IgM level of 29.95 AU/mL as the cutoff for grouping) was about 38.0% (19/50), which was twice as much as that in the IgM^lo group (18.4%; 9/49). The patients with positive chest imaging and lymphocytopenia (<1 × 10⁹/L) had a higher SARS-CoV-2-specific IgM level.

Conclusions: Quantitative SARS-CoV-2-specific IgM and IgG levels are helpful for the diagnosis, severity classification, and management of COVID-19 patients, and they should be monitored in each stage of this disease.

Keywords: COVID-19; Clinical significance; Serum IgG; Serum IgM; Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2).