Objective To compare the diagnostic values of cystatin C (CysC), β₂-microglobulin (β₂-MG), neutrophil gelatinase-associated lipocalin (NGAL) and retinol-binding protein (RBP) in acute kidney injury (AKI) in elderly patients with acute myocardial infarction (AMI).

Methods One hundred and twenty older patients with AMI admitted to Affiliated Hospital of Jiangnan University were retrospectively enrolled from January 2021 to January 2022. The serum levels of CysC, β₂-MG, NGAL, RBP and creatinine on day 1, and creatinine level on day 3 after admission were collected. According to KDIGO diagnostic criteria, the patients were grouped into AKI group and non-AKI group. The receiver operating characteristics (ROC) curve was used to evaluate the diagnostic value of CysC, β₂-MG, NGAL, RBP in AKI, and the correlation between serum levels of each indicator and eGFR was analyzed.

Results Compared with non-AKI group, the serum levels of CysC, β₂-MG and NGAL were significantly increased in AKI group (P < 0.05), RBP level had no significant change. The areas under the ROC curve (AUC) of CysC+β₂-MG+NGAL+RBP, CysC+β₂-MG, CysC, β₂-MG, NGAL and RBP were 0.941, 0.910, 0.909, 0.873, 0.747 and 0.729, and the sensitivity and specificity of CysC or β₂-MG were higher than NGAL or RBP. The serum levels of CysC (r=﹣0.762, P < 0.001) and β₂-MG (r=﹣0.683, P < 0.001) were negatively correlated with eGFR. The consistent results of AUC and association were found after removing the low ejection fractio (EF) value (< 50%).

Conclusions Compared with NGAL and RBP, serum CysC and β₂-MG levels may have higher values in diagnosing AKI in elderly patients with AMI and have greater associations with eGFR; the diagnostic value of multiple indicators is superior to the single.