Urinary retinol-binding protein as a risk factor of poor prognosis in acute-on-chronic renal injury.

BACKGROUND: Acute-on-chronic renal injury was commonly seen in clinical practice. Reversibility of acute-on-chronic renal injury had not yet been carefully explored. This study tested whether urinary biomarkers could be used as a noninvasive prognostic marker in patients with acute-on-chronic renal injury.

METHODS: 108 adult patients with pre-existing chronic kidney disease presenting with acute-on-chronic renal injury were included. Urinary retinol-binding protein (uRBP), N-Acetyl-b-D-Glucosaminidase (uNAG) and albumin (uALB) was quantified.

RESULTS: Reversibility of renal function was achieved in 43 patients of the 108 included patients. The levels of urinary retinol-binding protein, N-Acetyl-b-D-Glucosaminidase and albumin for non-recovery acute-on-chronic renal injury patients were much higher than recovery patients. The fourth quartiles of urinary retinol-binding protein were significantly associated with at least 1.055-fold odds of non-recovery and the urinary retinol-binding protein was an independent risk factor for outcome of acute-on-chronic renal injury patients by multivariate logistic regression analysis. Quartiles of both urinary N-Acetyl-b-D-Glucosaminidase and albumin had a graded relationship with the risk for un-recovery AKI. However, after a multivariate logistic analysis, the urinary N-Acetyl-b-D-Glucosaminidase and albumin was not associated with reversibility of acute-on-chronic renal injury.

CONCLUSION: In patients with acute-on-chronic renal injury, urinary retinol-binding protein was associated with the reversibility of kidney function. Quantification of urinary retinol-binding protein may be developed as a non-invasive tool for predicting outcome of acute-on-chronic renal injury patients.