Additional markers include: urinary β2-microglobulin, N-acetyl-β-glucosaminidase (NAG), and L-FABP, which are markers of rejection in urine tests used in real clinical practice, with β2-microglobulin assessing proximal tubule injury [41], NAG serving as a sensitive marker of tubular injury [37], and L-FABP being a valuable biomarker for diagnosing acute kidney injury and predicting long-term graft outcomes in kidney-transplant patients [42]. This evidence concerns the gene FABP1 and acute kidney injury.