Clinical characteristics of asymptomatic carriers of novel coronavirus disease 2019: A multi-center study in Jiangsu Province

Figures & data

Table 1. Clinical characteristics of the study subjects according to the disease severity of COVID-19

Characteristic	Disease severity of COVID-19				Statistic parameter
	Asymptomatic carriers (n = 50)	Mild cases (n = 81)	Ordinary cases (n = 486)	Severe or critical cases (n = 31)	F value/Chi-Square	P value
Mean (SD) age, years	41.37 ± 23.96 (n = 49)	39.85 ± 18.08 (n = 81)	46.03 ± 16.12 (n = 486)	60.84 ± 13.55 (n = 31)	12.543	< 0.001
Sex, male, n (%)	23/50 (46.0)	35/81 (43.2)	267/486 (54.9)	20/31 (64.5)	6.472	0.091
Smoker, n (%)	6/50 (12.0)	3/81 (3.7)	40/486 (8.2)	2/31 (6.5)	3.288	0.349
Exposure to source of transmission within 14 d before admission, n/total n (%)
Living in Wuhan	3/50 (6.0)	6/81 (7.4)	62/486 (12.8)	1/31 (3.2)	5.611	0.132
Contact with wildlife	0/50 (0)	0/81 (0)	1/486 (0.2)	0/31 (0)	0.334	0.954
Visited Wuhan recently	3/50 (6.0)	16/81(19.8)	90/486 (18.5)	4/31 (12.9)	5.682	0.128
Contact with Wuhan residents	14/50 (28.0)	14/81 (17.3)	121/486 (24.9)	4/31 (12.9)	4.748	0.191
Temperature on admission (°C)	36.65(36.40–36.80) (n = 48)	36.80 (36.53–37.28) (n = 80)	36.90 (36.50–37.50) (n = 475)	36.65 (36.50–37.20) (n = 30)	18.857	< 0.001
Fever	0/50 (0)	41/81 (50.6)	382/486 (78.6)	28/31 (90.3)	153.20	< 0.001
Symptoms on admission, n (%)
Conjunctival congestion	0/50 (0)	1/81 (1.2)	1/486 (0.2)	0/31 (0)	2.675	0.445
Nasal congestion	0/50 (0)	21/81 (25.9)	30/486 (6.2)	0/31 (0)	45.269	< 0.001
Headache	0/50 (0)	4/81 (4.9)	52/486 (10.7)	1/31 (3.2)	9.719	0.021
Cough	0/50 (0)	29/81 (35.8)	327/486 (67.3)	23/31 (74.2)	106.30	< 0.001
Sore throat	0/50 (0)	8/81 (9.9)	57/486 (11.7)	6/31 (19.4)	8.787	0.032
Sputum production	0/50 (0)	15/81 (18.5)	185/486 (38.1)	14/31 (45.2)	40.009	< 0.001
Fatigue	0/50 (0)	6/81 (7.4)	154/486 (31.7)	12/31 (38.7)	42.229	< 0.001
Hemoptysis	0/50 (0)	1/81 (1.2)	6/486 (1.2)	0/31 (0)	1.011	0.799
Shortness of breath	0/50 (0)	2/81 (2.5)	96/486 (19.8)	22/31 (71.0)	82.198	< 0.001
Nausea or vomiting	0/50 (0)	1/81 (1.2)	31/486 (6.4)	3/31 (9.7)	7.652	0.054
Diarrhea	0/50 (0)	5/81 (6.2)	56/486 (11.5)	8/31 (25.8)	15.541	0.001
Myalgia or arthralgia	0/50 (0)	9/81 (11.1)	83/486 (17.1)	4/31 (12.9)	11.639	0.009
Chills	0/50 (0)	2/81 (2.5)	65/486 (13.4)	6/31 (19.4)	16.809	0.001
Signs of infection on admission, n (%)
Throat congestion	0/50 (0)	17/81 (21.0)	60/486 (12.3)	2/31 (6.5)	14.102	0.029
Swollen tonsils	0/50 (0)	0/81 (0)	2/486 (0.4)	0/31 (0)	0.669	0.881
Lymph-node enlargement	0/50 (0)	0/81 (0)	0/486 (0)	0/31 (0)	NA	NA
Rash	0/50 (0)	0/81 (0)	1/486 (0.1)	1/31 (3.2)	9.147	0.027

SD: standard deviation; NA: not applicable.

The data presented are the means (standard deviations), numbers (percentages), or the medians and the interquartile ranges. The denominators of the patients included in the analysis are provided if they differed from the overall numbers in the group. Rounding may mean the percentages do not total 100.

Table 2. Radiographic characteristics of the study subjects according to the disease severity of COVID-19

Characteristic	Disease severity of COVID-19				Statistic parameter
	Asymptomatic carriers (n = 50)	Mild cases (n = 81)	Ordinary cases (n = 486)	Severe or critical cases (n = 31)	Chi-Square	P value
Abnormalities on chest computed tomography images before admission n/total n (%)
Ground-glass opacity	2/14 (14.3)	3/18 (16.7)	133/302 (44.0)	8/20 (40.0)	9.672	0.022
Local patchy shadowing	3/14 (21.4)	2/18 (11.1)	63/302 (20.9)	1/20 (5.0)	3.876	0.275
Bilateral patchy shadowing	3/14 (21.4)	1/18 (5.6)	133/302 (44.0)	15/20 (75.0)	21.451	< 0.001
Interstitial abnormalities	1/14 (7.1)	0/18 (0)	12/302 (4.0)	0/20 (0)	2.003	0.572

The data presented are numbers (percentages).

Table 3. Laboratory measurements of the study subjects according to the disease severity of COVID-19

Characteristic	Disease severity of COVID-19				Statistic parameter
	Asymptomatic carriers (n = 50)	Mild cases (n = 81)	Ordinary cases (n = 486)	Severe or critical cases (n = 31)	F value/ Chi-Square	P value
Routine blood test
Hemoglobin (g/L)	141.00 (127.25–153.75) (n = 36)	135.00 (123.00–150.00) (n = 57)	140.00 (128.00–152.00) (n = 318)	129.50 (121.25–156.75) (n = 24)	3.379	0.337
Platelet count (× 10^9/L)	230.50(191.00–255.00) (n = 40)	209.00 (158.75–269.50) (n = 62)	178.00 (142.00–218.00) (n = 349)	141.00 (116.00–168.00) (n = 23)	40.939	< 0.001
White blood cell count (× 10^9/L)	6.35 (5.03–7.38) (n = 40)	5.44 (4.63–6.97) (n = 66)	4.65 (3.80–5.83) (n = 373)	4.58 (4.00–7.47) (n = 24)	31.543	< 0.001
Neutrophil count (× 10^9/L)	3.46 (2.40–4.52) (n = 38)	3.23 (2.48–4.57) (n = 62)	2.79 (2.09–3.87) (n = 367)	3.93 (2.71–6.76) (n = 23)	13.626	0.003
Monocyte count (× 10^9/L)	0.50 ± 0.23 (n = 11)	0.44 ± 0.16 (n = 12)	0.41 ± 0.18 (n = 109)	0.33 ± 0.18 (n = 13)	1.928	0.128
Eosinophil count (× 10^9/L)	0.04 (0.02–0.14) (n = 40)	0.03 (0.01–0.07) (n = 67)	0.01 (0.00–0.04) (n = 377)	0.01 (0.00–0.01) (n = 23)	35.756	< 0.001
Lymphocyte count (× 10^9/L)	1.74 (1.37–2.79) (n = 38)	1.64 (1.05–2.20) (n = 62)	1.18 (0.87–1.59) (n = 367)	0.64 (0.46–1.03) (n = 24)	64.581	< 0.001
Blood biochemistry indicators
Potassium (mmol/L)	3.98 (3.51–4.32) (n = 32)	3.83 (3.55–4.19) (n = 57)	3.80 (3.58–4.12) (n = 311)	3.65 (3.35–3.75) (n = 18)	10.543	0.014
Sodium (mmol/L)	139.80 (137.85–141.78) (n = 32)	138.90 (136.35–141.40) (n = 57)	138.20 (136.00–140.78) (n = 312)	135.38 (133.00–139.10) (n = 18)	11.626	0.009
Blood urea nitrogen (mmol/L)	4.24 (3.40–5.11) (n = 40)	3.90 (3.00–4.52) (n = 58)	3.80 (3.08–4.68) (n = 324)	5.29 (4.19–12.41) (n = 17)	14.798	0.002
Creatinine (µmol/L)	56.50 (45.00–75.20) (n = 40)	53.00 (44.40–63.00) (n = 59)	62.20 (50.00–75.00) (n = 361)	67.00 (32.00–78.75) (n = 21)	10.726	0.013
Total serum bilirubin (µmol/L)	10.50 (7.46–15.75) (n = 38)	8.50 (6.80–14.40) (n = 65)	10.90 (7.50–15.38) (n = 364)	13.20 (8.69–16.50) (n = 20)	6.255	0.100
Albumin (g/L)	45.15 (43.00–48.53) (n = 38)	44.40 (41.55–48.40) (n = 65)	42.30 (39.10–45.50) (n = 342)	39.90 (32.75–44.25) (n = 17)	29.493	< 0.001
Aspartate aminotransferase (U/L) (n = 390)	20.70 (16.60–23.00) (n = 27)	21.00 (16.60–27.00) (n = 47)	25.00 (19.40–33.40) (n = 297)	43.00 (28.00–50.00) (n = 19)	33.585	< 0.001
Alanine aminotransferase (U/L) (n = 464)	22.00 (16.50–31.70) (n = 37)	23.20 (16.00–31.50) (n = 63)	25.00 (17.30–38.00) (n = 347)	30.80 (25.10–50.60) (n = 17)	6.094	0.107
Alkaline phosphatase (U/L)	84.10 (63.00–107.50) (n = 37)	70.00 (51.00–90.50) (n = 65)	65.00 (53.00–79.00) (n = 346)	67.00 (59.25–73.95) (n = 16)	15.747	0.001
Lactate dehydrogenase (U/L)	209.00(172.50–277.75) (n = 36)	194.00 (164.00–314.00) (n = 61)	228.00 (181.00–317.50) (n = 340)	375.00 (248.00–458.50) (n = 17)	16.800	0.001
Hemostasis parameters
Prothrombin time (s)	12.00 (11.28–12.60) (n = 42)	11.90 (11.20–12.70) (n = 71)	12.20 (11.38–13.10) (n = 422)	12.80 (11.20–13.70) (n = 27)	10.980	0.012
Activated partial thromboplastin time (s)	29.90 (26.25–35.80) (n = 41)	29.60 (26.50–36.05) (n = 69)	31.85 (28.70–36.90) (n = 422)	33.60 (31.80–36.80) (n = 27)	10.552	0.014
Fibrinogen (g/L)	2.64 (2.17–3.03) (n = 38)	3.01(2.57–3.55) (n = 64)	3.62 (2.86–4.33) (n = 401)	4.53 (2.84–6.07) (n = 26)	47.472	< 0.001

Table 4. Levels of Inflammatory markers and lymphocyte subsets of the study subjects according to disease severity of COVID-19

Characteristic	Disease severity of COVID-19					Statistic parameter
	Asymptomatic carriers (n = 50)	Mild cases (n = 81)	Ordinary cases (n = 486)	Severe or critical cases (n = 31)		F value/Chi-Square	P value
Inflammatory marker
Erythrocyte sedimentation rate (mm/h)	7.00 (4.25–13.00) (n = 32)	11.00 (5.00–25.75) (n = 38)	18.00 (8.00–32.00) (n = 239)		58.00 (33.50–75.00) (n = 17)	37.498	< 0.001
C-reactive protein > 10.0 mg/L	7/39 (17.9)	12/62 (19.4)	173/359 (48.2)		23/26 (88.5)	49.374	< 0.001
Procalcitonin (ng/mL)	0.03 (0.02–0.10) (n = 23)	0.03 (0.02–0.05) (n = 38)	0.04 (0.02–0.08) (n = 241)		0.15 (0.06–0.28) (n = 14)	13.243	0.004
Interleukin-6 (pg/mL)	0.01 (0.01–0.02) (n = 11)	0.01 (0.01–2.32) (n = 21)	0.02 (0.01–0.04) (n = 92)		0.03 (0.03–0.15) (n = 5)	5.774	0.123
Lymphocyte subset
CD3 + T lymphocytes (/µL)	1411.54 ± 671.25 (n = 13)	1431.06 ± 577.90 (n = 16)	1045.06 ± 501.65 (n = 89)		486.60 ± 266.28 (n = 5)	6.219	0.001
CD4 + T lymphocytes (/µL)	782.69 ± 366.39 (n = 13)	712.56 ± 350.52 (n = 16)	577.25 ± 300.94 (n = 89)		307.80 ± 164.67 (n = 5)	3.803	0.012
CD8 + T lymphocytes (/µL)	451.00 (286.50–634.00) (n = 13)	532.00(329.25–663.50) (n = 16)	316.00(216.00–526.50) (n = 89)		144.00 (62.50–259.00) (n = 5)	15.533	0.001

CD: cluster of differentiation.

Table 5. Spearman correlations between disease severity of COVID-19 and age, laboratory characteristics

Variables	Disease severity of COVID-19
	Correlation coefficient	P value
Age (years) (n = 647)	0.178	< 0.001
White blood cell count (×10^9/L) (n = 503)	−0.214	< 0.001
Neutrophils count (×10^9/L) (n = 490)	−0.051	0.257
Eosinophils count (×10^9/L) (n = 507)	−0.259	< 0.001
Lymphocyte count (×10^9/L) (n = 491)	−0.357	< 0.001
Platelet count (×10^9/L) (n = 474)	−0.289	< 0.001
Monocytes count (×10^9/L) (n = 145)	−0.189	0.023
Hemoglobin (g/L) (n = 435)	0.002	0.961
Potassium (mmol/L) (n = 418)	−0.110	0.025
Sodium (mmol/L) (n = 419)	−0.157	0.001
Blood Urea nitrogen (mmol/L) (n = 439)	−0.040	0.409
Creatinine (umol/L) (n = 481)	0.121	0.008
Total serum bilirubin (umol/L) (n = 487)	0.090	0.046
Albumin (g/L) (n = 462)	−0.251	< 0.001
Aspartate aminotransferase (U/L) (n = 390)	0.286	< 0.001
Alanine aminotransferase (U/L) (n = 464)	0.107	0.021
Alkaline phosphatase (U/L) (n = 464)	−0.147	0.001
Lactate dehydrogenase (U/L) (n = 454)	0.159	0.001
Prothrombin time (s) (n = 562)	0.135	0.001
Activated partial thromboplastin time (s) (n = 559)	0.137	0.001
Fibrinogen (g/L) (n = 529)	0.294	< 0.001
Erythrocyte sedimentation rate (mm/h) (n = 326)	0.311	< 0.001
Procalcitonin (ng/mL) (n = 316)	0.165	0.003
Interleukin-6 (pg/ml) (n = 129)	0.183	0.038
CD3 + T lymphocytes (/ul) (n = 123)	−0.340	< 0.001
CD4 + T lymphocytes (/ul) (n = 123)	−0.290	0.001
CD8 + T lymphocytes (/ul) (n = 123)	−0.322	< 0.001

CD: cluster of differentiation.

Table 6. Association between disease severity of COVID-19 and laboratory characteristics by multiple regression analysis

Variable	Mild cases (n = 81)		Ordinary cases (n = 486)		Severe and critical cases (n = 31)
	OR(95%CI)	P value	OR(95%CI)	P value	OR(95%CI)	P value
Platelet count (×10^9/L) (n = 474)	0.997(0.992–1.002)	0.199	0.991(0.986–0.995)	< 0.001	0.979(0.969–0.989)	< 0.001
White blood cell count (×10^9/L) (n = 503)	0.923(0.779–1.093)	0.351	0.755(0.649–0.879)	< 0.001	0.913(0.725–1.149)	0.437
Lymphocyte count (×10^9/L) (n = 491)	0.794(0.564–1.118)	0.187	0.383(0.259–0.567)	< 0.001	0.029(0.007–0.114)	< 0.001
Potassium (mmol/L) (n = 418)	0.685(0.351–1.336)	0.267	1.010(0.836–1.221)	0.917	0.283(0.097–0.830)	0.021
Albumin (g/L) (n = 462)	0.953(0.877–1.036)	0.258	0.881(0.820–0.947)	0.001	0.837(0.754–0.930)	0.001
Aspartate aminotransferase (U/L) (n = 390)	0.987(0.933–1.045)	0.657	1.045(1.000–1.093)	0.052	1.071(1.021–1.124)	0.005
Alanine aminotransferase (U/L) (n = 464)	1.008(0.983–1.034)	0.517	1.018(0.996–1.040)	0.109	1.031(1.004–1.058)	0.024
Fibrinogen (g/L) (n = 529)	1.512(0.929–2.460)	0.096	2.514(1.661–3.888)	< 0.001	3.597(2.171–5.960)	< 0.001
Erythrocyte sedimentation rate (mm/h) (n = 326)	1.044(1.005–1.085)	0.028	1.047(1.011–1.084)	0.009	1.086(1.044–1.129)	< 0.001
C-reactive protein (mg/L) (n = 486)	0.882(0.305–2.549)	0.817	0.246(0.103–0.585)	0.002	0.042(0.010–0.186)	< 0.001
CD3 + T lymphocytes (/ul) (n = 123)	1.000(0.999–1.001)	0.777	0.999(0.998–1.000)	0.040	0.995(0.990–0.999)	0.024
CD4 + T lymphocytes (/ul) (n = 123)	0.999(0.997–1.001)	0.382	0.998(0.997–1.000)	0.050	0.994(0.987–1.000)	0.042
CD8 + T lymphocytes (/ul) (n = 123)	1.000(0.998–1.003)	0.717	0.999(0.996–1.001)	0.215	0.998(0.976–1.000)	0.047

CD: cluster of differentiation; OR: odds ratio; CI: confidence interval.

Table 7. Receiver operating characteristic curve analyses for diagnostic predictor of asymptomatic carriers of COVID-19

Variables	AUC (95% CI)	P value	Cutoff	Sensitivity	Specificity	Youden index
White blood cell count (×10^9/L) (n = 503)	0.715(0.647–0.782)	< 0.001	5.015	0.811	0.571	0.382
Lymphocyte count (× 10^9/L) (n = 491)	0.740(0.665–0.814)	< 0.001	1.365	0.784	0.598	0.382
Eosinophils count (×10^9/L) (n = 507)	0.720(0.651–0.789)	< 0.001	0.015	0.792	0.548	0.340
Neutrophils count(×10^9/L) (n = 490)	0.585(0.506–0.663)	0.048	3.5	0.549	0.654	0.203
Platelet count (×10^9/L) (n = 474)	0.696(0.626–0.766)	0.036	190.5	0.755	0.582	0.337
Hemoglobin (g/L) (n = 435)	0.520(0.434–0.607)	0.651	121.5	0.894	0.178	0.072
Monocytes count (×10^9/L) (n = 145)	0.632(0.473–0.790)	0.147	0.365	0.818	0.5	0.318
Potassium (mmol/L) (n = 418)	0.632(0.545–0.720)	0.003	3.885	0.681	0.604	0.285
Sodium (mmol/L) (n = 419)	0.648(0.579–0.718)	0.001	139.17	0.681	0.594	0.275
Blood Urea nitrogen (mmol/L) (n = 439)	0.574(0.498–0.651)	0.077	3.995	0.648	0.561	0.209
Creatinine (umol/L) (n = 481)	0.425(0.339–0.512)	0.074	15.1	0.981	0.047	0.028
Aspartate aminotransferase (U/L) (n = 390)	0.358(0.271–0.445)	0.004	13.55	1	0.028	0.028
Total serum bilirubin(umol/L) (n = 487)	0.481(0.400–0.562)	0.658	5.95	0.904	0.136	0.04
Alanine-aminotransferase (U/L) (n = 464)	0.449(0.367–0.532)	0.237	6.40	1	0.007	0.007
Alkaline phosphatase (U/L) (n = 464)	0.695(0.611–0.778)	< 0.001	82.70	0.569	0.797	0.366
Albumin (g/L) (n = 462)	0.692(0.627–0.758)	< 0.001	42.65	0.846	0.52	0.366
Lactate dehydrogenase (U/L) (n = 454)	0.425(0.348–0.501)	0.082	142.00	1	0.052	0.052
Activated partial thromboplastin time (s) (n = 559)	0.401(0.322–0.481)	0.015	273.00	0.018	1	0.018
Prothrombin time (s) (n = 562)	0.444(0.378–0.510)	0.166	1.025	1	0.101	0.101
Fibrinogen (g/L) (n = 529)	0.234(0.173–0.295)	< 0.001	1.895	1	0.025	0.025
Procalcitonin (ng/mL) (n = 316)	0.393(0.287–0.499)	0.042	0.1815	0.147	0.872	0.019
Interleukin-6 (pg/ml) (n = 129)	0.253(0.143–0.363)	< 0.001	4.98	0.048	0.963	0.011
Erythrocyte sedimentation rate (mm/h) (n = 326)	0.275(0.201–0.349)	< 0.001	-	-	-	-
CD3^+ T lymphocytes (/ul) (n = 123)	0.678(0.545–0.811)	0.008	1416.5	0.522	0.82	0.342
CD4^+ T lymphocytes (/ul) (n = 123)	0.640(0.507–0.773)	0.036	501.0	0.783	0.53	0.313
CD8^+ T lymphocytes (/ul) (n = 123)	0.671(0.550–0.792)	0.011	421.0	0.696	0.65	0.346

AUC: area under the curve; CI: confidence interval; CD cluster of differentiation.

Figure 1. Receiver operating characteristic curve analyses of leukocytes, lymphocytes, eosinophils, and platelets as diagnostic predictors of asymptomatic carriers of COVID-19. ROC: receiver operating characteristic; WBC: white blood cell; PLT: platelet

Figure 2. Receiver operating characteristic curve analyses of interleukin-6 and procalcitonin as diagnostic predictors of asymptomatic asymptomatic carriers of COVID-19. ROC: receiver operating characteristic; IL-6: interleukin-6; PCT: procalcitonin

Figure 3. Receiver operating characteristic curve analyses of aspartate aminotransferase, albumin, potassium, and sodium as diagnostic predictors of asymptomatic asymptomatic carriers of COVID-19. ROC: receiver operating characteristic; AST: aspartate aminotransferase; ALB: albumin; K: potassium; Na: sodium

Figure 4. Receiver operating characteristic curve analyses of the activated partial thromboplastin time and fibrinogen as diagnostic predictors of asymptomatic asymptomatic carriers of COVID-19. ROC: receiver operating characteristic; APTT: activated partial thromboplastin time; FIB: fibrinogen

Figure 5. Receiver operating characteristic curve analyses of cluster of differentiation (CD)3+, CD4+, and CD8+ lymphocyte levels as diagnostic predictors of asymptomatic asymptomatic carriers of COVID-19. ROC: receiver operating characteristic; CD: cluster of differentiation