DLL4 and non-proliferative diabetic retinopathy: The serum DLL4 level was significantly greater in the NDR group (43.38 ± 16.23 pg/mL), NPDR group (56.57 ± 25.89 pg/mL), and PDR group (74.97 ± 25.28 pg/mL) than in the healthy controls (29.9 ± 8.92 pg/mL; all p < 0.05).