Table 2.

Summary of selected studies analyzing levels of Vascular Endothelial Growth Factor (VEGF) in association with presence of varying stages of diabetic retinopathy.

Sample analyzed	Study design	Sample size	Key findings	Method of analysis
VEGF (plasma)	Cavusoglu et al., 2007/Cross sectional	N = 83 (31 NPDR, 34 PDR,18 healthy controls)	VEGF levels increased significantly between NPDR and PDR (P = 0.016) and also between diabetics with NPDR vs. healthy controls (p < 0.000) as well as between PDR and healthy controls (p < 0.000)	ELISA (Biosource) sensitive to VEGF-165
VEGF (serum)	Du et al., 2014/Cross sectional (see also Table 4)	N = 69 diabetic patients (30 NDR, 23 NPDR, 16 PDR)	Increasing serum VEGF trend between no DR, NPDR and PDR groups; higher levels of VEGF in PDR vs. NPDR and NDR (p = 0.007 and p < 0.001, respectively); VEGF levels in NPDR vs. NDR also significantly higher (p = 0.007)	ELISA (human VEGF ELISA kit, Rapid Bio Lab, Calabasas, CA, USA)
VEGF (serum)	Jain et al., 2013/cross sectional	N = 77 (19 NDR, 19 NPDR, 20 PDR, 19 healthy controls)	VEGF levels were significantly different between the study groups (p < 0.001) by ANOVA	Human VEGF ELISA kit, Invitrogen
VEGF (serum)	Ozturk et al., 2009/cross sectional	N = 156 (31 NDR, 49 NPDR, 46 PDR, 28 healthy controls)	VEGF levels higher in those with NPDR compared to controls (p = 0.01), and in PDR compared to controls (p = 0.02). No significant difference between NPDR and PDR (p = 0.87)	Luminex multiplex bead immunoassay (Human Cytokine LINCOplex kit; LINCO Research, St Charles, MO)

VEGF, Vascular Endothelial Growth Factor; NDR, diabetic with no retinopathy; NPDR, non-proliferative diabetic retinopathy; PDR, proliferative diabetic retinopathy.