Table 2. The main characteristics of the included studies on the relationship of NLR and PLR to DR.
| First author | Year | Study design | Country | No. of patients |
Age mean/median | Male/female | NOS | ||
| Non-DR | NPDR | PDR | |||||||
| Akdoğan[26] | 2016 | Retrospective | Turkey | 158 | 120 | Non-DR: 57.3±12.2 | Non-DR: 59/99 | 7 | |
| DR: 59.8±9.2 | DR: 47/73 | ||||||||
| Ciray[50] | 2015 | Retrospective | Kazakhstan | 59 | 55 | Non-DR: 57.8±11.5 | NR | 6 | |
| DR: 61.8±10.8 | |||||||||
| Kuang[51] | 2015 | Retrospective | China | 62 | 44 | 22 | Non-DR: 60.73±11.24 | Non-DR: 29/33 | 6 |
| NPDR: 60.50±8.45 | NPDR: 17/27 | ||||||||
| PDR: 55.18±13.05 | PDR: 11/11 | ||||||||
| Öztürk[56] | 2013 | Retrospective | Turkey | 97 | 79 | NR | NR | NR | 5 |
| Shen[52] | 2016 | Retrospective | China | 118 | 134 | 58 | Non-DR: 55.19±5.51 | Non-DR: 63/55 | 6 |
| NPDR: 58.04±7.53 | NPDR: 73/61 | ||||||||
| PDR: 59.84±8.76 | PDR: 34/24 | ||||||||
| Ulu[53] | 2013 | Retrospective | Turkey | 34 | 24 | NR | NR | 5 | |
| Wei[42] | 2017 | Retrospective | China | 94 | 52 | 40 | Non-DR: 58.14±11.93 | Non-DR: 50/44 | 6 |
| DR: 58.42±12.09 | DR: 49/43 | ||||||||
| Wang[54] | 2015 | Retrospective | China | 138 | 131 | Non-DR: 60.3±6.0 | Non-DR: 65/73 | 7 | |
| DR: 66.6±5.8 | DR: 53/78 | ||||||||
| Yin[55] | 2015 | Retrospective | China | 64 | 28 | 36 | Non-DR: 56.83±9.01 | Non-DR: 35/29 | 6 |
| NPDR: 53.09±8.82 | NPDR:13/15 | ||||||||
| PDR: 53.16±10.64 | PDR:19/17 | ||||||||
| Yue[45] | 2015 | Retrospective | China | 125 | 62 | 59 | Non-DR: 56.00±3.75 | Non-DR: 73/52 | 6 |
| NPDR: 53.50±3.56 | NPDR: 34/28 | ||||||||
| PDR: 56.0±3 | PDR: 28/31 | ||||||||
| Zhou[46] | 2016 | Retrospective | China | 328 | 51 | Non-DR: 57±16 | Non-DR: 198/130 | 6 | |
| DR: 63±15 | DR: 34/17 | ||||||||
DR: Diabetic retinopathy; NR: Not reported; NPDR: Non-proliferative diabetic retinopathy; PDR: Proliferative diabetic retinopathy; NLR: Neutrophil to lymphocyte ratio; PLR: Platelet-lymphocyte ratio.