CCL21 and type 2 diabetes mellitus: It was found that urinary small EVs derived CCL21 expression could discriminate patients with DN from patients with T2DM efficiently, with the area under the ROC curve (AUC) of 0.888 (95% CI 0.752–1) (Fig. 2E), which is more efficient than level of eGFR and proteinuria (AUC of eGFR, 0.225 with 95% CI 0.065–0.385, AUC of proteinuria, 0.748 with 95% CI 0.577–0.920).