Dynamic Plasma suPAR Levels For Predicting DGF And Early Warning Of Long-Term Renal Function Progression After Kidney Transplantation

To explore the predictive value of dynamically monitoring plasma soluble urokinase-type plasminogen activator receptor (suPAR) levels before and after surgery for delayed graft function (DGF) following allogeneic renal transplantation, and to analyze its correlation with long-term progression of graft function.

A retrospective cohort study was conducted, enrolling 195 patients who underwent allogeneic renal transplantation in our hospital from April 2018 to September 2021. Patients were divided into the DGF group (n=38) and the Immediate Graft Function (IGF) group (n=157) based on whether dialysis was required within 7 days after surgery. Using plasma samples stored in the hospital's biobank, suPAR levels were measured by Enzyme-Linked Immunosorbent Assay (ELISA) before surgery, and at 24 hours, 3 days, and 7 days after surgery. Renal function was followed up until 24 months postoperatively or until the occurrence of an endpoint event (a ≥30% decrease in estimated Glomerular Filtration Rate [eGFR] from baseline). Baseline characteristics and suPAR levels were compared between the two groups. Receiver Operating Characteristic (ROC) curves were used to evaluate the efficacy of suPAR in predicting DGF. Kaplan-Meier survival curves and log-rank tests were applied to analyze the relationship between suPAR and renal function progression.

There were statistically significant differences between the DGF group and the IGF group in terms of donor type (deceased donor proportion: 94.7% vs. 73.2%, P=0.004), pre-donation serum creatinine of donors (109.55±61.31 vs. 84.67±64.19 μmol/L, P<0.001), warm ischemia time (4.84±1.20 vs. 3.93±1.41 min, P<0.001), pre-operative serum creatinine of recipients (1117.24±394.65 vs. 977.97±315.93 μmol/L, P=0.013), and pre-operative white blood cell count (7.43±2.96 vs. 6.23±1.79×10⁹/L, P=0.017). The plasma suPAR levels in the DGF group were significantly higher than those in the IGF group at all time points. The areas under the ROC curves  of plasma suPAR for predicting DGF before surgery, at 24 hours, 3 days, and 7 days after surgery were 0.624 (95% confidence interval [CI]: 0.522-0.725, P=0.018), 0.696 (0.605-0.787, P<0.001), 0.756 (0.676-0.835, P<0.001), and 0.692 (0.601-0.783, P<0.001), respectively. The sensitivity/specificity under the corresponding optimal cut-off values were 36.8%/87.3%, 55.3%/81.5%, 81.6%/61.1%, and 44.7%/83.4%, respectively. Survival analysis showed that the risk of a 30% decrease in eGFR in the high suPAR level group was significantly higher than that in the low suPAR level group at 24 hours (hazard ratio [HR]=1.75, 95% CI: 1.03-2.99, P=0.039) and 7 days (HR=1.93, 95% CI: 1.13-3.31, P=0.016) after surgery. However, there were no statistically significant differences before surgery (HR=1.38, 95% CI: 0.81-2.32, P=0.233) and at 3 days after surgery (HR=1.20, 95% CI: 0.71-2.01, P=0.501).

Dynamic monitoring of plasma suPAR levels can serve as a biomarker for early identification of DGF after renal transplantation, with the 3-day post-operative measurement showing the best predictive value. Elevated plasma suPAR levels at 24 hours and 7 days postoperatively indicate an increased risk of long-term renal function progression, providing an important reference for early clinical intervention.