Comparative Assessment of uNGAL, uNAG and Cystatin C As Early Biomarkers in Renal Post-Transplant Patients

Urinary neutrophil gelatinase-associated lipocalin (uNGAL), urinary N-acetyl-bd-glucosaminidase (NAG), urinary α1-microglobulin/creatinine ratio and cystatin C have been suggested as potential early markers of delayed graft function (DGF) following kidney transplantation. We conducted a prospective study in 50 consecutive kidney transplant recipients to evaluate serial changes of these biomarkers within the first week after transplantation and assess their performance in predicting DGF (dialysis requirement during initial post-transplant week) and graft function throughout the first year. Urine samples were collected on post-transplantation days 0, 1, 2, 4, and 7. Statistical analysis: Linear mixed and multivariable regression models, receiver-operating characteristic (ROC), and areas under ROC curves were used. At all-time points, mean urinary NGAL levels were significantly higher in patients developing DGF. Shortly after transplantation (3-6 h), uNGAL and uNAG values were higher in DGF recipients (on average +242 ng/mL; NAG – 6.8 U/mmol creatinine, considering mean dialysis time of 4.1 years) and rose further in the following days, contrasting with prompt function recipients. On Day-1 uNGAL levels accurately predicted DGF (AUC-ROC = 0.93), with a performance higher than serum creatinine (AUC-ROC = 0.76), and similar to cystatin C (AUC-ROC = 0.95). Multivariable analyses revealed that uNGAL levels at days 4 and 7 were strongly associated with one-year serum creatinine level. Urinary NGAL, serum cystatin C is an early marker of graft injury and is independently associated with dialysis requirement within one week after transplantation and one-year graft function.