MO366: Renal Functional Reserve as a Marker to Stratify the Risk of Kidney Injury in Hematopoietic Stem Cell Transplantation
Authors: Mancianti Nicoletta , Guarnieri Andrea , Lenoci Mariapia , Toraldo Francesca , Paola Salvo Domenica , Belluardo Massimo , Marotta Giuseppe , Garosi Guido 
Published: May 2022

Abstract

BACKGROUND AND AIMS
Haematopoietic stem cell transplantation (HSCT) is an effective treatment for myelo-lymphoproliferative disorders. Acute kidney injury (AKI) is a major complication of HSCT (incidence ≈15%–60%), usually occurs in the first 100 days post-transplant, and is associated with a significant increase in mortality and morbidity. In addition, it can lead to chronic renal failure (CKD). There are no scores to predict which patients will develop AKI or CKD post-HSCT. Routine pre-HSCT evaluation only considers the estimated glomerular filtrate value (eGFR) without examining the renal functional reserve (RFR). RFR is defined as the ability of the kidney to increase its glomerular filtration rate in response to higher functional demand (as in the case of HSCT).

METHOD
This prospective study aimed to evaluate the ability of RFR in HSCT candidate patients to stratify the risk of AKI incidence within 100 days of transplantation and predict eventual functional recovery. The secondary purpose was to identify the risk factors for the onset of AKI.
A total of 41 HSCT candidate patients with normal baseline GFR (bGFR) were included in the study. A total of 15 days before the HSCT, a multiparametric nephrological evaluation and RFR test (RFR-T) were performed using an oral protein load (1–1.2 g/kg) with freeze-dried products (Prother®) and 10 mL/kg of oral hydration. GFR after protein loading (glomerular stress filtration rate, sGFR) and bGFR were measured with body surface corrected endogenous creatinine clearance (CrCl). Blood samples were taken at predefined time intervals concerning oral protein load (120–180–240 min). RFR was defined as the difference between the maximum value of sGFR and bGFR expressed as a percentage (normal RFR &gt; 25%).

RESULTS
No correlation was found between bGFR and RFR values. Consistent with the literature, 25 of 41 patients (61%) developed AKI. Comparing the group that developed AKI with those that did not, no statistically significant differences emerged related to demographic, clinical, or multiparameter screening characteristics. RFR was lower in AKI + patients than in AKI- patients, with a value at the borderline of statistical significance (P = 0.06). Among the 25 patients who developed AKI, 7 patients (30%) recovered normal renal function in the follow-up, while 18 patients (70%) developed CKD. 71% of patients who recovered renal function demonstrated an RFR value&gt;25%; no demographic and multiparameter screening variables correlated with the development of post-HSCT CKD.

CONCLUSION
RFR is a dynamic parameter with respect to the bGFR. It allows the identification of conditions of subclinical functional deterioration, capable of affecting both the onset of AKI and CKD post-HSCT. No other multiparameter screening variable has shown potential utility in this type of predictive assessment. The stratification of the risk of kidney injury through RFR represents the most promising marker in this sense. A reliable prediction of the risk of renal complication in these patients could lead to accurate multidisciplinary management able to improve the prognosis quoad vitam (severe in the case of AKI post-HSCT) and quoad valetudinem (severe in case of CKD post-HSCT).