Third, although we excluded patients with known CKD stage 4 or 5 from enrollment because baseline CKD can result in elevated baseline NGAL concentrations, our inclusion of patients with known CKD stage 3 could lead to some confounding because CKD Stage 3 has been associated with elevated baseline NGAL concentrations in elderly patients who developed AKI after iodinated contrast administration (mean 150.8 ± 77.8 ng/ml).35 The gene discussed is LCN2; the disease is chronic kidney disease.