| Coding | Source literature | Fasting c-peptide (ng/ml) | Reference range of fasting c-peptide (ng/ml) |
| 1 | Gaudy et al., 2015 [35] | Undetectable | Unknown |
| 2 | Mellati e t Al., 2015 [21] | 0.3 | 1.0~7.1 |
| 3 | Hughes et al., 2015 [22] | 0.5 | 1.1~4.4 |
| 4 | Thoreau et al., 2017 [36] | 0.08 | Unknown |
| 5 | Miyoshi et al., 2016 [37] | 0.23 | 0.8.~2.3 |
| 6 | Okamoto et al., 2016 [38] | <0.1 | 0.61~2.09 |
| 7 | Aleksova et al., 2016 [39] | 0.015 | 0.08~0.64 |
| 8 | Hofmann et al., 2016 [26] | 0.004 | 0.038~0.226 |
| 9 | Shah et al., 2016 [40] | 0.81 | Unknown |
| 10 | Farrell et al., 2017 [41] | Undetectable | Unknown |
| 11 | Ishikawa et al., 2017 [42] | <0.1 | 0.8.~2.5 |
| 12 | Zaied et al., 2018 [13] | 0.4 | 1.1~4.4 |
| 13 | Zeng et al., 2019 [43] | <0.01 | 0.78~1.89 |
| 14 | Cheng et al., 2018 [44] | <0.01 | 0.37~1.47 |
| 15 | Hickmott, et al. 2017 [45] | 0.65 | Unknown |
| 16 | Gu et al. 2020 [46] | Undetectable | Unknown |
| 17 | Wang et al., 2021 [47] | 0.2 | 1.1~5.0 |
| 18 | He et al., 2020 [48] | 0.01 | 0.78.~5.79 |
| 19 | Li et al., 2018 [49] | 0.51 | 1.1~4.4 |
| 20 | Wu et al., 2021 [50] | 0.07 | 0.78~5.19 |
| 21 | Code 1 | <0.02 | 1.1~4.4 |
| 22 | Code 4 | 0.74 | 1.1~4.4 |
| 23 | Code 5 | <0.02 | 1.1~4.4 |