Association of FIB-4 and APRI with Contrast-Associated Acute Kidney Injury in Patients with Non-ST-Segment Elevation Myocardial Infarction Undergoing Coronary Angiography

Background/Objectives: In patients with non-ST-segment elevation myocardial infarction (NSTEMI), contrast-associated acute kidney injury (CA-AKI) is a clinically important complication of coronary angiography. Whether the Fibrosis-4 (FIB-4) index and aspartate aminotransferase-to-platelet ratio index (APRI) relate to CA-AKI in this setting is unclear. We compared the associations of both indices with CA-AKI. Methods: We retrospectively analyzed 771 patients with NSTEMI who underwent coronary angiography from May 2020 to May 2025. CA-AKI was identified from changes in serum creatinine 48–72 h after contrast administration. Both indices were derived from admission laboratory values. Associations were evaluated using separate multivariable logistic regression models. Discrimination was compared using the paired DeLong test, and the incremental performance of FIB-4 beyond the Mehran score was explored. Results: Overall, 97 patients (12.6%) developed CA-AKI. In the primary adjusted model, FIB-4 was associated with CA-AKI (odds ratio 1.19, 95% confidence interval 1.04–1.36; p = 0.013), but APRI was not. FIB-4 showed modest discrimination but a significantly higher area under the receiver operating characteristic curve (AUC) than APRI (0.614 versus 0.535; DeLong p < 0.001). Adding FIB-4 to the Mehran score improved model fit (likelihood-ratio p = 0.009), but the increase in AUC from 0.646 to 0.666 was not statistically significant (DeLong p = 0.100). Sensitivity analyses showed that the association varied with covariate adjustment. Conclusions: FIB-4 was associated with CA-AKI in the primary adjusted model and showed higher discrimination than APRI. These findings support further investigation of FIB-4 as a potential adjunct to renal risk assessment, although its modest discrimination and uncertain incremental clinical value require independent validation.