Urinary Biomarkers and Kidney Injury in VA NEPHRON-D: Phenotyping Acute Kidney Injury in Clinical Trials

Rationale & Objective: Urinary biomarkers of injury, inflammation, and repair may help phenotype acute kidney injury (AKI) observed in clinical trials. We evaluated the differences in biomarkers between participants randomized to monotherapy or to combination renin-angiotensinaldosterone system (RAAS) blockade in VA NEPHRON-D, where an increased proportion of observed AKI was acknowledged in the combination arm. Study Design: Longitudinal analysis. Setting & Participants: A substudy of the VA NEPHRON-D trial. Predictor: Primary exposure was the treatment arm (combination [RAAS inhibitor] vs monotherapy). AKI is used as a stratifying variable. Outcome: Urinary biomarkers, including albumin, EGF (epidermal growth factor), MCP -1 (monocyte chemoattractant protein -1), YKL-40 (chitinase 3like protein 1), and KIM -1 (kidney injury molecule -1). Analytical Approach: Biomarkers measured at baseline and at 12 months in trial participants were compared between treatment groups and by AKI. AKI events occurring during hospitalization were predefined safety end points in the original trial. The results were included in a metaanalysis with other large chronic kidney disease trials to assess global trends in biomarker changes. Results: In 707 participants followed for a median of 2.2 years, AKI incidence was higher in the combination (20.7%) versus the monotherapy group (12.7%; relative risk [RR], 1.64 [95% CI, 1.16-2.3 0]). Compared with the monotherapy arm, in the combination arm the urine biomarkers at 12 months were either unchanged (MCP -1: RR, -3% [95% CI, -13% to 9%], Padj = 0.8; KIM -1: RR, -10% [95% CI, -20% to 1%], Padj = 0.2; EGF, RR -7% [95% CI, -12% to -1%], Padj = 0.08) or lower (albuminuria: RR, -24% [95% CI, -37% to -8%], Padj = 0.02; YKL: RR, -40% to -44% [95% CI, -58% to -25%], Padj < 0.001). Pooled meta -analysis demonstrated reduced albuminuria in the intervention arm across 3 trials and similar trajectories in other biomarkers. Limitations: Biomarker measurement was limited to 2 time points independent of AKI events. Conclusions: Despite the increased risk of serum creatinine-defined AKI, combination RAAS inhibitor therapy was associated with unchanged or decreased urinary biomarkers at 12 months. This suggests a possible role for kidney biomarkers to further characterize kidney injury in clinical trials.