Association Between the Modified Renal Angina Index and Major Adverse Kidney Events at 90 Days in Critically Ill Adults: A Retrospective Cohort Study

Background/Objectives: Adult modified Renal Angina Index (mRAI) formulations predict acute kidney injury, but their association with major adverse kidney events at 90 days (MAKE90) remains unclear. We examined the association in critically ill adults without established chronic kidney disease (CKD). Methods: This retrospective cohort included 250 adults admitted to a tertiary intensive care unit (ICU) between December 2023 and April 2025. mRAI was calculated from data available at ICU admission. MAKE90 was defined as death, renal replacement therapy, or persistent renal dysfunction within 90 days. We used logistic regression, receiver operating characteristic analysis, and nested-model comparisons. Results: Admission mRAI was higher in patients with MAKE90 than in those without MAKE90 (median 10 [IQR 5–20] vs. 3 [IQR 1–6]; p < 0.001). After adjustment for SOFA score and sepsis, mRAI remained associated with MAKE90 (adjusted OR per point from the linear model, 1.073; 95% CI, 1.032–1.116). Spline analysis demonstrated a significant nonlinear association (p = 0.004), indicating that the per-point OR should be interpreted as a summary estimate rather than a constant effect across the score range. The AUC of mRAI was 0.752 (95% CI, 0.691–0.814), higher than that of admission AKI stage (0.653) and not significantly different from APACHE II (0.702) or SOFA (0.718). Adding mRAI to SOFA and sepsis raised the AUC from 0.735 to 0.782. Conclusions: In critically ill adults without established CKD, higher admission mRAI remained associated with MAKE90 after adjustment for SOFA score and sepsis and showed moderate discrimination. External validation in larger, independent cohorts is needed to confirm these findings.