However, in our study, the RRI was not correlated with the CD34 PPA-total or CD34 PPA-peritubular capillary from CKD stages 2 to 5, a result that is attributable to the diverse composition of the study samples (the RRI values were ≤0.7 in all patients; patients with CKD4-5 were fewer; in the composition of patients with CKD, the glomeruli are mainly damaged or the glomeruli are invaded first). Here, CD34 is linked to chronic kidney disease.