Rationale for the evaluation of renal functional reserve in allogeneic stem cell transplantation candidates: a pilot study

Background: The main purpose of our study was to evaluate the ability of renal functional reserve (RFR) to stratify the risk of acute kidney injury (AKI) occurrence within 100 days of hematopoietic stem cell transplantation (HSCT) and to predict any functional recovery or the onset of chronic kidney disease. A secondary aim was to identify the clinical/laboratory risk factors for the occurrence of AKI.

Methods: The study design is prospective observational. We enrolled 48 patients with normal basal glomerular filtration rate (bGFR) who underwent allogenic HSCT. A multiparameter assessment and the Renal Functional Reserve Test (RFR-T) using an oral protein load stress test were performed 15 days before the HSCT.

Results: Different RFRs corresponded to the same bGFR values. Of 48 patients, 29 (60%) developed AKI. Comparing the AKI group with the group that did not develop AKI, no statistically significant difference emerged in any characteristic related to demographic, clinical or multiparameter assessment variables except for the estimated GFR (eGFR). eGFR ≤100 mL/min/1.73 m² was significantly related to the risk of developing AKI (Fisher's exact test, P = .001). Moreover, RFR-T was lower in AKI+ patients vs AKI- patients, but did not allow statistical significance (28% vs 40%). In AKI patients, RFR >20% was associated with complete functional recovery (one-sided Fisher's exact test, P = .041). The risk of failure to recover increases significantly when RFR ≤20% (odds ratio = 5.50, 95% confidence interval = 1.06-28.4).

Conclusion: RFR identifies subclinical functional deterioration conditions essential for post-AKI recovery. In our cohort of patients with no kidney disease (NKD), the degree of pre-HSCT eGFR is associated with AKI risk, and a reduction in pre-HSCT RFR above a threshold of 20% is related to complete renal functional recovery post-AKI. Identifying eGFR first and RFR second could help select patients who might benefit from changes in transplant management or early nephrological assessment.