The PRESERVE trial used a 2 × 2 factorial design to compare intravenous saline solution with intravenous sodium bicarbonate solution and oral N-acetylcysteine with placebo for the prevention of 90-day major adverse kidney events and death (MAKE-D) and contrast-associated acute kidney injury (CA-AKI) among patients with chronic kidney disease undergoing angiography. In this ancillary study, we evaluated the predictive capacities of preangiography injury and repair proteins in urine and plasma for MAKE-D, CA-AKI, and their impact on trial design.