Table 2. Results of meta-analysis and subgroup analysis.

	No. of studies	OR(95%CI)	P-Value	Heterogeneity		Model used
				I²	Ph
Hypertension	6	2.29(1.69-3.10)	<0.001	4.0%	0.391	Fixed
ICU care	2	2.97(0.70-12.55)	<0.001	55.7%	0.133	Romdon
Clinical symptoms	4	2.03(1.45-2.85)	<0.001	0	0.947	Fixed
Diabetes	6	2.47(1.67-3.66)	<0.001	39.3%	0.144	Fixed
ICU care	2	1.24(0.07-22.98)	0.883	82.0%	0.018	Romdon
Clinical symptoms	4	2.66(1.73-4.10)	<0.001	0	0.429	Fixed
COPD	6	5.97(2.49-14.29)	<0.001	0	0.995	Fixed
ICU care	2	8.30(1.26-54.43)	0.027	0	0.885	Fixed
Clinical symptoms	4	5.37(1.99-14.46)	0.001	0	0.973	Fixed
Liver disease	5	0.67(0.30-1.49)	0.326	0	0.573	Fixed
ICU care	2	0.41(0.05-3.53)	0.713	0	0.416	Fixed
Clinical symptoms	3	0.74(0.31-1.75)	0.492	16.9%	0.300	Fixed
Malignancy	4	2.29(1.00-5.23)	0.049	0	0.627	Fixed
ICU care	2	1.67(0.49-5.61)	0.410	0	0.547	Fixed
Clinical symptoms	2	3.18(1.05-9.64)	0.041	0	0.370	Fixed
Renal disease	4	2.51(0.93-6.78)	0.070	0	0.501	Fixed
ICU care	1	2.94(0.40-21.69)	0.290	-	-	-
Clinical symptoms	3	2.38(0.76-7.50)	0.237	15.0%	0.308	Fixed
Cardiovascular disease	4	2.93(1.73-4.96)	<0.001	0	0.989	Fixed
ICU care	2	2.69(1.14-6.34)	0.023	0	0.924	Fixed
Clinical symptoms	2	3.10(1.59-6.02)	0.001	0	0.834	Fixed
Cerebrovascular disease	3	3.89(1.64-9.22)	0.002	44.8%	0.163	Fixed
ICU care	1	20.20(2.34-174.44)	0.006	-	-	-
Clinical symptoms	2	2.07(0.70-6.12)	0.189	0	0.852	Fixed