Association between inflammatory burden index combined with D-dimer and acute kidney injury in elderly patients

Background The interplay between inflammation and coagulation is central to the pathophysiology of acute kidney injury (AKI). This study aimed to explore the association between IBI and the incidence of AKI in the elderly, as well as the intricate connections between IBI, D-dimer, and AKI. Methods The data came from the clinical records of patients aged ≥ 65 years hospitalized at Wuhan Tongji Hospital between January 2018 and December 2022. We evaluated the predictive efficacy of IBI and other inflammatory indicators for AKI by receiver operating characteristic (ROC) analysis. Restricted cubic spline (RCS) and Logistic regression models were employed to examine the correlation between IBI, D-dimer, and AKI risk. Furthermore, ROC analysis, integrated discrimination improvement (IDI), and net reclassification improvement (NRI) were performed to assess the predictive value of the combined IBI-D-dimer index. The bidirectional mediating effects of IBI and D-dimer in AKI were validated using the bootstrap method. Results This study involved 69,738 participants. The median age was 71.24 (67.75, 76.46) years, and 25,831 (37.0%) were female. During hospitalization, 3,755 (5.4%) elderly patients developed AKI. ROC analysis demonstrated that, compared to conventional inflammatory indicators, Log IBI had superior predictive value for AKI in elderly patients (AUC = 0.719, 95% CI 0.711–0.727, p < 0.001). In multivariate analyses, the highest quartile of Log IBI (OR = 2.526, 95% CI 2.193–2.918, p < 0.001) and D-dimer levels (OR = 2.493, 95% CI 2.184–2.854, p < 0.001) were independently linked to an elevated risk of AKI. A significant multiplicative interaction between Log IBI and D-dimer was observed ( p -interaction < 0.001). The combined index further improved risk reclassification, with participants exhibiting concurrent elevations of both markers conferring the highest AKI risk (OR = 2.640, 95% CI 2.328–3.002, p < 0.001). Mediation analysis revealed bidirectional effects: D-dimer mediated 31.30% ( p < 0.001) of Log IBI’s association with AKI, while Log IBI mediated 6.18% ( p < 0.001) of D-dimer’s effect. Conclusion Concurrent elevation of IBI and D-dimer was associated with the greatest risk of elderly AKI. The dynamic monitoring of IBI and D-dimer may help identify high-risk elderly patients for AKI.