Myeloperoxidase (MPO) is an oxidative stress biomarker, with elevated MPO levels linked to chronic kidney disease (CKD) progression. Metal exposure is a risk factor for CKD, and is also correlated to MPO expression, with specific MPO genotypes linked to MPO expression. Therefore, we examined whether MPO plasma levels or MPO polymorphisms were linked to CKD, and explored whether these factors modified associations between CKD and metal concentrations. Accordingly, we recruited 395 age- and sex-matched controls and 215 patients with CKD (persistent estimated glomerular filtration rate (eGFR) <
60 mL/min/1.73 m