Serum Vascular Endothelial Growth Factor Levels Correlate with Severity of Retinopathy in Diabetic Patients: A Systematic Review and Meta-Analysis

Table 2

Subgroup analysis of the included studies.

Subgroups	No. of studies	SMD (95% CI)		Test of heterogeneity
				Serum
Study location
Asia	13	0.74 (0.42-1.07)	<0.001	91.3%	<0.001
Europe	5	0.39 (−0.20-0.98)	0.199	81.5%	<0.001
Africa	1	3.22 (2.06-4.38)	<0.001	/	/
Study design
Cross-sectional	12	0.91 (0.54-1.29)	<0.001	92.5%	<0.001
Case-control	6	0.13 (−0.11-0.36)	0.283	25.0%	0.246
Cohort	1	3.22 (2.06-4.38)	<0.001	/	/
Plasma
Study location
Asia	7	0.09 (−0.14-0.31)	0.463	93.7%	<0.001
Europe	2	0.54 (−0.21-1.29)	0.156	0.0%	0.729
South America	1	−0.12 (−0.84-0.59)	0.734	/	/
Study design
Cross-sectional	8	0.54 (−0.12-1.20)	0.108	91.7	<0.001
Case-control	1	−0.38 (−0.88-0.12)	0.557	/	/
Cohort	1	0.07 (−0.17-0.31)	0.133	/	/