A recent observational analysis of the Chronic Renal Insufficiency Cohort (CRIC), which enrolled approximately 4000 patients with CKD in the United States (US), showed that serum MPO levels were associated with the risk of renal outcome, defined as initiation of RRT, 50% eGFR decline, or eGFR ≤ 15 mL/min/1.73 m2 [44]. This evidence concerns the gene MPO and chronic kidney disease.