Diagnostic Accuracy of the Delta Neutrophil Index in Predicting Sepsis-Associated Acute Kidney Injury: A...

Sepsis-associated acute kidney injury (SA-AKI) is a worldwide health concern. It necessitates prompt and precise diagnosis of sepsis and renal dysfunction. The delta neutrophil index (DNI), C-reactive protein (CRP), procalcitonin, and serum lactate are potential biomarkers for early detection of SA-AKI. Hence, we conducted this study to evaluate the diagnostic accuracy of DNI in predicting SA-AKI among patients with sepsis and to calculate the area under the curve (AUC). We also compared the same with those of CRP, procalcitonin, and serum lactate.

This cross-sectional study was carried out at Kalinga Institute of Medical Sciences (KIMS), Bhubaneswar, India, from March 2024 to February 2026. We enrolled adult sepsis patients from the medicine intensive care unit (ICU) during this period. We excluded referred cases, patients with sepsis before ICU admission, and those with prior renal dysfunction. White blood cell (WBC) count, serum creatinine, estimated glomerular filtration rate (eGFR), CRP, procalcitonin, serum lactate, DNI, and the Sequential Organ Failure Assessment (SOFA) scores were evaluated on days 0, 1, 3, and 7. We calculated the sensitivity, specificity, and diagnostic accuracy of CRP, procalcitonin, serum lactate, DNI, and SOFA scores. We used R software version 4.6.1 (R Foundation for Statistical Computing, Vienna, Austria) for data analysis.

We enrolled 937 patients with sepsis. Their median age was 56.0 (48.0-67.0) years. The study population was predominantly male (569, 60.73%). Two hundred thirty-four (24.97%) participants had SA-AKI. The median WBC counts among participants without and with AKI on day 0 were 18.5 (16.9-20.7) x 10⁹/L and 20.4 (18.4-22.8) x 10⁹/L, respectively (p < 0.001). Their median baseline serum creatinine values were 1.05 (0.96-1.12) mg/dL and 1.06 (0.97-1.16) mg/dL, respectively (p = 0.063). The corresponding median baseline DNI values were 8.0 (7.1-8.6)% and 9.1 (8.2-10.2)%, respectively (p < 0.001). On day 7, the DNI values were 7.0 (6.4-7.7)% and 8.4 (7.6-9.0)%, respectively (p < 0.001). Their median CRP values were 17.1 (14.4-20.9) mg/dL and 26.2 (22.6-30.2) mg/dL, respectively (p < 0.001). The median procalcitonin values were 1.98 (1.68-2.34) ng/mL and 2.11 (1.91-2.36) ng/mL, respectively (p < 0.001). The median serum lactate values were 2.6 (2.0-3.2) mmol/L and 2.6 (1.9-4.6) mmol/L, respectively (p = 0.004). All these parameters decreased over time. The sensitivity values for CRP, DNI, procalcitonin, serum lactate, and SOFA scores were 0.799, 0.594, 0.880, 0.308, and 0.026, respectively. Their specificity values were 0.764, 0.804, 0.351, 0.920, and 0.982, respectively. The corresponding diagnostic accuracy values were 0.773, 0.752, 0.483, 0.767, and 0.743, respectively. The AUCs for CRP, DNI, procalcitonin, serum lactate, and SOFA scores were 0.855 (0.831-0.880), 0.753 (0.716-0.790), 0.593 (0.556-0.630), 0.562 (0.515-0.610), and 0.436 (0.393-0.479), respectively.

DNI values were significantly lower in patients with sepsis without AKI than in those with AKI. The diagnostic accuracy of DNI was comparable to CRP. Our results show that baseline DNI is a potential marker of SA-AKI, which can predict downstream risks of renal impairment in sepsis.