Lactate-to-Albumin Ratio for Predicting Post-Contrast Acute Kidney Injury After Contrast-Enhanced CT in the Emergency Department

Objective: To evaluate the association between the lactate-to-albumin ratio (LAR) and the development of post-contrast acute kidney injury (PC-AKI) in patients undergoing intravenous contrast-enhanced computed tomography (CT) in the emergency department (ED), and to compare its discriminative performance with other biomarker ratios. Methods: This retrospective observational study included adult patients who underwent contrastenhanced CT in a tertiary ED between January 2022 and January 2025. Patients with available baseline and 48-72-hour post-contrast serum creatinine measurements were analyzed. LAR, blood urea nitrogen-to-albumin ratio (BAR), C-reactive protein-to-albumin ratio (CAR), and neutrophil-tolymphocyte ratio (NLR) were calculated using laboratory values obtained at ED presentation. Logistic regression analyses were performed, and receiver operating characteristic curves were constructed. Results: A total of 695 patients were included, and PC-AKI occurred in 43 (6.2%). Patients with PCAKI were older and had higher hemoglobin, creatinine, blood urea nitrogen, C-reactive protein, and lactate levels, as well as lower albumin and estimated glomerular filtration rate values (all p<0.05). LAR, BAR, CAR, and NLR differed between groups. In multivariable analysis, LAR (OR=3.898; 95% CI: 2.799-5.430; p<0.001), BAR (OR=1.635; 95% CI: 1.171-2.283; p=0.004), and NLR (OR=1.820; 95% CI: 1.359-2.438; p<0.001) were associated with PC-AKI. LAR showed an area under the curve of 0.854, with a sensitivity of 88.4% and a negative predictive value of 98.9% at a cut-off of >0.51. Conclusion: LAR measured at ED presentation was associated with the development of PC-AKI following contrast-enhanced CT and demonstrated higher discriminative performance compared with other evaluated ratios. These findings suggest that LAR may be useful for risk stratification in this clinical context.