CCN1 and diabetes mellitus: The areas under the receiver operating characteristic curves for DR were 0.730 (95% CI: 0.644–0.817), 0.713 (95% CI: 0.625–0.802), and 0.684 (95% CI: 0.593–0.775) for CCN1 levels, HbA1c levels, and duration of diabetes, respectively, whereas no significant differences were observed for age, urea, and BMI (all p > 0.05; Table 2; Figure 1).