1Department of Laboratory Medicine, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China. 2Department of Infectious Diseases, Xixi Hospital of Hangzhou, Hangzhou, China. 3State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China. 4National Clinical Research Center for Infectious Diseases, Hangzhou, China. 5Zhejiang Provincial Key Laboratory for Diagnosis and Treatment of Aging and Physic-chemical Injury Diseases, Hangzhou, China
Up to now, little is known about the detailed immune profiles of COVID-19 patients from admission to discharge. In this study we retrospectively reviewed the clinical and laboratory characteristics of 18 COVID-19 patients from January 30, 2020 to February 21, 2020. These patients were divided into two groups; group 1 had a severe acute respiratory syndrome coronavirus 2 nucleic acid-positive duration for more than 15 days (n = 6) and group 2 had a nucleic acid-positive duration for less than 15 days (n = 12). Group 1 patients had lower level of peripheral blood lymphocytes (0.40 vs. 0.78 ×109/L, p = 0.024) and serum potassium (3.36 vs. 3.79 mmol/L, p = 0.043) on admission but longer hospitalization days (23.17 vs. 15.75 days, p < 0.001) compared to Group 2 patients. Moreover, baseline level of lymphocytes (r = -0.62, p = 0.006) was negatively correlated with the nucleic acid-positive duration. Additionally, lymphocytes (420.83 vs. 1100.56 /μL), T cells (232.50 vs. 706.78 /μL), CD4+ T cells (114.67 vs. 410.44 /μL), and CD8+ T cells (94.83 vs. 257.44 /μL) in the peripheral blood analyzed by flow cytometry were significantly different between Group 1and Group 2. Furthermore, there was also a negative correlation between lymphocytes (r = -0.54, p = 0.038) or T cells (r = -0.55, p = 0.034) at diagnosis and the nucleic acid-positive duration, separately. In conclusion, the patients with nucleic acid-positive ≥ 15 days had significantly decreased lymphocytes, T cell and its subsets compared to those who remained positive for less than 15 days.
Table 1 Characteristics of COVID-19 patients on admission.
Figure 1. Correlation analysis between lymphocytes count and the duration of nucleic acid-positive of COVID-19 patients. Lymphocytes count in peripheral blood (A) but not serum potassium level (B) at admission was negatively correlated with the SARS-CoV-2 nucleic acid-positive duration. Spearman correlation analysis was performed. p<0.05 as statistical significance.
Cytokines
Normal range
COVID-19 patients (n = 17)
Nucleic acid-positive < 15 days (n = 11)
Nucleic acid-positive ≥ 15 days (n = 6)
p value1
IFN-γ (pg/mL)
0.00-20.06
13.08 ± 15.96
9.06 ± 8.69
20.45 ± 23.75
0.302
IL-10 (pg/mL)
0.00-2.31
5.83 ± 4.91
4.15 ± 3.29
8.92 ± 6.14
0.052
IL-2 (pg/mL)
0.00-4.13
1.26 ± 0.55
1.08 ± 0.36
1.6 ± 0.71
0.143
IL-4 (pg/mL)
0.00-8.37
2.05 ± 1.93
1.50 ± 0.24
3.05 ± 3.14
0.281
IL-6 (pg/mL)
0.00-6.61
29.51 ± 19.10
23.82 ± 15.38
39.94 ± 22.20
0.097
TNF-α (pg/mL)
0.00-33.27
38.44 ± 41.46
22.49 ± 20.92
67.69 ± 55.14
0.103
Table 2 Characteristics of serum cytokines of COVID-19 patients at diagnosis.
Lymphocyte subsets
Normal range
COVID-19 patients (n = 15)
Nucleic acid-positive < 15 days (n = 9)
Nucleic acid-positive ≥ 15 days (n = 6)
p value†
At diagnosis
At discharge1
At diagnosis
At discharge2
At diagnosis
At discharge3
Lymphocytes (/μL)
1530-3700
828.67 ± 700.99
1301.53 ± 566.77*
1100.56 ± 784.76
1372.89 ± 558.81
420.83 ± 240.61
1194.50 ± 613.92*
0.035*
T cells (/μL)
955-2860
517.07 ± 496.82
906.87 ± 412.71*
706.78 ± 567.01
949.44 ± 424.35
232.50 ± 121.53
843.00 ± 425.02*
0.038*
CD3+CD4+CD8- T cells (/μL)
550-1440
292.13 ± 323.05
524.07 ± 294.16*
410.44 ± 375.48
548.67 ± 332.58
114.67 ± 60.32
487.17 ± 250.17*
0.047*
CD3+CD4-CD8+ T cells (/μL)
320-1250
192.40 ± 170.89
324.53 ± 186.26*
257.44 ± 191.84
339.33 ± 147.95
94.83 ± 62.08
302.33 ± 247.24
0.039*
CD4+/CD8+ ratio
0.71-2.78
1.69 ± 1.11
2.05 ± 1.18
1.81 ± 1.27
1.86 ± 1.13
1.51 ± 0.90
2.32 ± 1.30
0.629
B cells (/μL)
90-560
168.40 ± 135.75
221.73 ± 111.09*
219.44 ± 148.39
226.44 ± 131.06
91.83 ± 68.10
214.67 ± 83.52*
0.072
NK cells (/μL)
150-1100
120.13 ± 82.92
140.93 ± 123.40
148.56 ± 91.59
179.78 ± 118.71
77.50 ± 46.82
82.67 ± 115.31
0.106
Table 3 Lymphocyte subsets in COVID-19 patients at diagnosis and at discharge.
Figure 2. Correlation analysis between lymphocyte subset numbers and the nucleic acid-positive duration of COVID-19 patients. Lymphocytes count in peripheral blood (A) and T cells (B) at diagnosis were negatively correlated with the duration of SARS-CoV-2 nucleic acid-positive. CD4+ T cells (C) and CD8+ T cells (D) were not correlated with the duration of SARS-CoV-2 nucleic acid-positive. Spearman correlation analysis was performed. p<0.05 as statistical significance.
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