Urine albumin-to-creatinine ratio for early diagnosis and risk stratification of acute kidney injury in high-risk critically ill ICU patients: A prospective cohort study

Abstract

Background Acute kidney injury (AKI) is common in the intensive care unit (ICU) but is often detected only after creatinine rises or oliguria develops. Although novel biomarkers allow earlier detection, their cost limits use. The urine albumin-to-creatinine ratio (uACR) is inexpensive, yet its role in AKI risk stratification remains uncertain. Methods In a prospective single-centre cohort of mixed ICU patients, adults with existing AKI or at high risk (modified AKI Risk Based on Creatinine [ARBOC] score ≥ 3) were enrolled. uACR was measured at enrollment (uACR at Time 0) and 24 h (uACR at Time 1). Outcomes included the prevalence and prognostic value of elevated uACR (≥ 3.4 mg/mmol) for incident, progressive, or persistent AKI (> 48 h), and for ≥30% decline in estimated glomerular filtration rate (eGFR) at discharge. Predictive performance was assessed using the area under the receiver operating characteristic curve (AUC), change in AUC, net reclassification improvement (NRI), integrated discrimination improvement (IDI), and decision-curve analysis. Results Of 1010 patients screened, 203 were analysed (89 with and 114 without AKI at enrollm). Elevated uACR was frequent (72% with AKI; 52% without). In AKI patients, high uACR correlated with longer and more persistent AKI. Discrimination for incident AKI was modest (AUC 0.61 and 0.66 for uACR at Time 0 and uACR at Time 1) but higher for persistent AKI (both AUC 0.68). Adding uACR at Time 0 to ARBOC improved reclassification (NRI 0.48; IDI 0.04) and clinical net benefit. Conclusions uACR modestly identified incident AKI and more strongly predicted persistent AKI. As a simple biomarker, uACR may serve as a low-cost adjunct to existing ICU risk stratification tools, but requires further validation before consideration for routine clinical use.