Characteristics of asymptomatic COVID-19 infection and progression: A multicenter, retrospective study

Figures & data

Figure 1. Flow chart of the cohort study.

Table 1. Demographics and baseline characteristics of the asymptomatic patients with COVID-19.

Characteristics	Value		P value
	Asymptomatic patients (n = 79)	Symptomatic patients (n = 1489)
Age
Median(IQR) (range)	60.00 (41.00,70.00) (9–96 yr)	60.00(49.00,68.00) (14–100 yr)	0.663
Age distribution (n, %)
<18 yr*	2(2.53)	6(0.40)	0.003
18–45 yr*	23(29.11)	270(18.10)
46–65 yr*	24(30.38)	712(47.82)
≥66 yr	30(37.97)	501(33.65)
Sex (n, %)
Male	32(40.51)	617(41.44)	0.870
Female	47(59.49)	872(58.56)
Coexisting disorder (n, %)
Respiratory disease	1(1.27)	83(5.57)	0.122
Coronary heart disease	3(3.80)	77(5.17)	0.781
Diabetes	16(20.25)	174(11.69)	0.023
Hypertension	17(21.52)	416(27.94)	0.214
Cerebrovascular disease	4(5.06)	50(3.36)	0.622
Chronic hepatopathy	1(1.27)	22(1.48)	1.000
Chronic renal disease	3(3.80)	15(1.00)	0.058
Cancer	5(6.33)	33(2.22)	0.039
Presence of no less than two comorbidities	14(17.72)	299(20.08)	0.668
Abnormalities on chest CT(n, %)
Unilateral	12(15.19)	207(13.90)	0.077
Bilateral	60(75.95)	1225(82.27)
No abnormalities*	7(8.86)	57(3.83)
Ground-glass opacity	19(24.05)	410(27.54)	0.498
Patchy shadowing	47(59.49)	985(66.15)	0.224
Interstitial abnormalities	7(8.86)	65(4.37)	0.113
Thickening of the adjacent pleura	11(13.92)	186(12.49)	0.708
Clinical classification (n, %)
Mild	7(8.86)	57 (3.83)	<0.001
Moderate	70(88.61)	1166(78.31)
Severe	2(2.53)	217(14.57)
Critical	0(0)	49(3.29)
Clinical outcome			0.505
Discharged	79(100.00)	1465(98.39)
Died	0(0)	24(1.61)

Data are presented as median (IQR) or n (%);*P < 0.05 vs. the symptomatic group; IQR: interquartile ranges; COVID-19: novel coronavirus disease 2019; CT: computed tomography.

Table 2. Laboratory findings of the asymptomatic patients with COVID-19.

Characteristics	Value		P value
	Asymptomatic patients (n = 79)	Symptomatic patients (n = 1489)
Blood routine test
Leukocyte (×10⁹/L; normal range 3.50–9.50)	5.60 (4.70,7.10)	5.60 (4.70,6.70)	0.778
Neutrophils (×10⁹/L; normal range 1.80–6.30)	3.39 (2.73,4.63)	3.41 (2.64,4.36)	0.985
Lymphocyte (×10⁹/L; normal range 0.10–3.20)	1.64 (1.32,2.04)	1.60 (1.26,2.00)	0.579
Monocyte (×10⁹/L; normal range 0.10–0.60)	0.35 (0.27,0.45)	0.38 (0.30,0.47)	0.046
Platelet (×10⁹/L; normal range 125.00–350.00)	210.00 (184.00,247.00)	218.00 (179.00,261.00)	0.596
Blood biochemistry
Albumin (g/L; normal range 35.00–52.00)	38.70 (36.43,41.68)	38.80 (36.10,41.10)	0.596
Alanine aminotransferase (U/L; normal range 0.00–55.00)	15.00 (10.20,26.10)	21.00 (13.70,34.20)	<0.001
Aspartate aminotransferase (U/L; normal range 5.00–34.00)	15.20 (12.40,20.10)	16.20 (12.80,22.60)	0.244
Total bilirubin (μmol/L; normal range 0.00–21.00)	9.25 (6.82,13.72)	9.50 (7.40,12.80)	0.764
Blood urea nitrogen (mmol/L; normal range 3.10–8.80)	4.47 (3.72,5.68)	4.56 (3.73,5.59)	0.771
Serum creatinine (μmol/L; normal range 49.00–90.00)	63.90 (54.70,72.10)	63.85 (55.00,75.80)	0.474
Creatine kinase (U/L; normal range 0.00–190.00)	60.00 (44.50,106.75)	56.00 (41.00,79.00)	0.302
Myoglobin (ng/mL; normal range 0.00–146.90)	34.60 (24.88,58.65)	33.50 (25.70,45.10)	0.268
Glucose (mmol/L; normal range 3.89–5.83)	4.64 (4.25,5.89)	4.80 (4.36,5.52)	0.342
Coagulation function
Activated partial thromboplastin time (s; normal range 21.00–37.00)	32.60 (29.95,35.75)	31.70 (29.60,34.10)	0.132
Prothrombin time (s; normal range 9.20–15.00)	11.60 (10.70,12.10)	11.40 (10.90,12.00)	0.938
D-dimer (mg/L; normal range 0.00–0.55)	0.26 (0.15,0.56)	0.34 (0.21,0.77)	0.077
Infection-related biomarkers
Procalcitonin (ng/mL; normal range 0.00–0.050)	0.04 (0.04,0.05)	0.04 (0.04,0.06)	0.149
Erythrocyte sedimentation rate (mm/h; normal range 0.00–15.00)	24.00 (12.00,66.00)	26.00 (12.00,55.00)	0.987
C-reactive protein (mg/L; normal range 0.00–10.00)	0.94 (0.40,2.15)	1.50 (0.56,4.00)	0.019
PLR	98.40 (131.43,162.10)	132.88 (103.25,176.24)	0.414
NLR	2.06 (1.57,2.83)	2.08 (1.58,2.90)	0.636
LMR	4.60 (3.48,6.38)	4.30 (3.24,5.50)	0.071

Data are presented as median (IQR) or n (%). IQR: interquartile ranges; COVID-19: novel coronavirus disease 2019; CT: computed tomography. PLR: platelet-to-lymphocyte ratio; NLR: neutrophil-to-lymphocyte ratio; LMR: lymphocyte-to-monocyte ratio

Table 3. The clinical features of the presymptomatic patients and the completely asymptomatic patients with COVID-19.

	Value
Characteristics	Presymptomatic patients (n = 34)	Completely asymptomatic patients (n = 45)	P value
Age
Median (IQR) (range)	68.50(49.00,80.50) (16–96 yr)	55.00(37.50,64.00) (9–85 yr)	0.002
Distribution -(n, %)
<18 yr	1 (2.94)	1 (2.22)	0.008
18–45 yr	7 (20.59)	16 (35.56)
46–65 yr*	6 (17.65)	18 (40.00)
≥66 yr*	20 (58.82)	10 (22.22)
Sex(female) (n, %)			0.135
Male	17 (50.00)	15 (33.33)
Female	17 (50.00)	30 (66.67)
Coexisting disorder (n, %)
Asthma	0 (0)	1 (2.22)	1.000
Diabetes	10 (29.41)	6 (13.33)	0.078
Hypertension	15 (44.12)	2 (4.44)	<0.001
Coronary heart disease	3 (8.82)	0 (0)	0.076
Cerebrovascular disease	2 (5.88)	2 (4.44)	1.000
Chronic renal disease	3 (8.82)	0 (0)	0.076
Cancer	3 (8.82)	2 (4.44)	0.647
Total with≥2 comorbidity	11 (32.35)	3 (6.67)	0.003
Abnormalities on chest CT (n, %)
Unilateral	7 (20.59)	5 (11.11)	0.185
Bilateral	25 (73.53)	35 (77.78)
No abnormalities	2 (5.88)	5 (11.11)
Ground-glass opacity	6 (17.65)	13 (28.89)	0.247
Patchy shadowing	23 (67.65)	24 (53.33)	0.199
Interstitial abnormalities	4 (11.76)	4 (8.89)	0.720
Thickening of the adjacent pleura	6 (17.65)	5 (11.11)	0.615
Blood routine test
Leukocytes (× 10⁹ per L; normal range 3.50–9.50)	5.50 (60,7.20)	5.70 (4.75,7.10)	0.801
Neutrophils (× 10⁹ per L; normal range 1.80–6.30)	3.25 (2.67,4.81)	3.42 (2.75,4.41)	0.972
Lymphocytes (× 10⁹ per L; normal range 1.10–3.20)	1.58 (1.31,1.95)	1.69 (1.31,2.12)	0.461
Monocyte (× 10⁹ per L; normal range 0.10–0.60)	0.39 (0.28,0.48)	0.35 (0.27,0.44)	0.349
Platelets (×10⁹per L; normal range 125.00–350.00)	204.50 (177.25,237.50)	213.00 (187.00,250.00)	0.223
Neutrophil percentage (%; normal range 40.00–75.00)	62.00 (57.50,66.45)	59.00 (52.15,67.85)	0.744
lymphocytes percentage (%; normal range 20.00–50.00)	29.90 (23.45,33.23)	30.70 (23.95,36.50)	0.329
Monocytes percentage (%; normal range 3.00–10.00)	6.15 (4.88,7.55)	6.10 (5.15,7.25)	0.988
Blood biochemistry
Albumin (g/L; normal range 35.00–52.00)	37.75 (35.40,39.28)	40.20 (37.60,41.80)	0.004
Alanine aminotransferase (U/L; normal range0.00–55.00)	14.90 (8.50,21.30)	15.35 (10.30,27.80)	0.309
Aspartate aminotransferase (U/L; normal range5.00–34.00)	16.10 (13.80,23.38)	14.25 (12.10,19.33)	0.090
Total bilirubin (μmol/L; normal range 0.00–21.00)	10.70 (6.13,13.55)	8.80 (7.13,13.95)	0.592
Blood urea nitrogen (mmol/L; normal range 3.10–8.80)	4.58 (3.74,6.27)	4.43 (3.71,5.22)	0.592
Serum creatinine (μmol/L; normal range 49.00–90.00)	67.05 (60.05,80.55)	59.50 (52.80,65.70)	0.008
Glucose (mmol/L; normal range 3.89–5.83)	4.64 (4.28,6.94)	4.55 (4.17,5.28)	0.287
Infection-related biomarkers
C-reactive protein (mg/L; normal range 0.00–10.00)	1.14 (0.50,4.56)	0.89 (0.23,1.92)	0.112
PLR	133.10(99.10,151.22)	129.50 (97.70,167.90)	0.905
NLR	2.10 (1.60,3.00)	1.94 (1.55,2.80)	0.411
LMR	4.17 (3.15,5.11)	5.42 (3.49,7.02)	0.069
Nucleic acid qPCR test
Nucleic acid positive duration	14.00 (7.00,25.00)	12.00 (5.00,24.00)	0.749
Redetected qPCR+	3 (8.82)	5 (11.11)	1.000
Incubation period	8.00 (5.00,12.00)
Treatment
TraditionalChinese medicine	34 (100.00)	45 (100.00)
antiviral therapy	32 (94.12)	38 (84.44)	0.286

Data are presented as median (IQR) or n (%); *P < 0.05 vs. the symptomatic group; IQR: interquartile ranges; COVID-19: novel coronavirus disease 2019; CT: computed tomography; qPCR: quantitative polymerase chain reaction; PLR: platelet-to-lymphocyte ratio; NLR: neutrophil-to-lymphocyte ratio; LMR: lymphocyte-to-monocyte ratio.

Table 4. Multivariate analysis of the presymptomatic patients and the completely asymptomatic patients with COVID-19.

Variable	B	SE	Wald	P value	OR	OR 95% CI
Age	1.629	0.766	4.528	0.033	5.100	1.137–22.870
Hypertension	2.150	0.854	6.334	0.012	8.583	1.609–45.785

B: partial regression coefficient; SE: standard error: Wald: Wald test statistic: OR: odds ratio; CI: confidence interval; COVID-19: novel coronavirus disease 2019.