The results of Pearson correlation analysis showed that the serum RBP4 level in the observation group was negatively correlated with GFR (r = −0.661, P < 0.001), that is, it was positively correlated with the condition of CKD; serum sRAGE level was positively correlated with GFR (r = 0.524, P = 0.019), that is, it was negatively correlated with the condition of CKD, as shown in Figure 3. Here, RBP4 is linked to chronic kidney disease.