HAMP and acute kidney injury: In a pilot study of a nested cohort of 22 patients with AKI and 22 without AKI, Ho et al. [14] reported a greater postoperative signal/noise ratio for urine hepcidin levels in those patients who did not go on to develop AKI, suggesting that hepcidin may be the first clinically useful negative biomarker for AKI after CPB.