Queen's University School of Medicine
Non-invasive differentiation of non-rejection kidney injury from acute rejection in pediatric renal transplant recipients
Ben Archdekin1, Atul Sharma2, Ian W. Gibson3, David Rush4, David S. Wishart5, Tom D. Blydt-Hansen6.
1Faculty of Health Sciences, Queen's University, Kingston, ON, Canada; 2Department of Pediatrics and Child Health, University of Manitoba, Children's Hospital at Health Sciences Center, Winnipeg, MB, Canada; 3Department of Pathology, University of Manitoba, Health Sciences Center, Winnipeg, MB, Canada; 4Department of Medicine, University of Manitoba, Health Sciences Center, Winnipeg, MB, Canada; 5The Metabolomics Innovation Center, University of Alberta, Edmonton, AB, Canada; 6Department of Pediatrics, University of British Columbia, BC Children's Hospital, Vancouver, BC, Canada
Introduction: Acute kidney injury (AKI) is a major concern in pediatric kidney transplant recipients 1-4, where non-alloimmune causes must be distinguished from rejection. We sought to identify a urinary metabolite signature associated with non-rejection kidney injury (NRKI) in pediatric kidney transplant recipients.
Methods: Urine samples (n=396) from 60 pediatric transplant participants were obtained at time of kidney biopsy and quantitatively assayed for 133 metabolites by mass spectrometry. Metabolite profiles were analyzed via projection on latent structures discriminant analysis. Mixed effects regression identified laboratory and clinical predictors of NRKI and distinguished NRKI from T-cell-mediated rejection (CMR), antibody-mediated rejection (AMR), and mixed CMR-AMR. Urine samples (n=199) without rejection were split into NRKI (n=26; ΔSCr ≥25%), Pre-AKI (n=35; ΔSCr ≥ 10% and < 25%), and No AKI (n=138; ΔSCr < 10%) groups. See Tables 1 and 2 for patient characteristics.
Results: The NRKI discriminant score (dscore) was able to distinguish between NRKI and No AKI (AUC) =0.86; 95% CI = 0.79-0.94). See Figure 1a. This was confirmed by leave-one-out cross-validation (AUC=0.79; 95% CI = 0.68-0.89). The NRKI dscore also distinguished between NRKI and Pre-AKI (AUC=0.82; 95% CI = 0.71-0.93). See Figure 1b.
In a linear mixed-effects regression model to account for repeated measures, the NRKI dscore was independent of concurrent rejection, but there was a non-statistical trend for higher dscores with rejection severity.
The NRKI discriminant equation was applied to previously excluded samples with sub-clinical rejection (n= 140) and clinical rejection (n=36), The difference in mean scores between groups was significant (ANOVA p<0.05) and pairwise testing confirmed significant differences between NRKI and each of No AKI, sub-clinical rejection, and clinical rejection. See Figure 2a.
The discriminant equation was also applied to samples with pure CMR (n=86), pure AMR (n=27), and Mixed CMR/AMR (n=62). The difference between groupings was significant (ANOVA p<0.05), and in pairwise comparison the mean NRKI dscore for the NRKI group was significantly higher than pure CMR, pure AMR, and Mixed CMR/AMR. See Figure 2b.
A second exploratory classifier developed to distinguish NRKI from clinical rejection had similar test characteristics (LOOCV AUC = 0.65 (95% CI = 0.51-0.79).
Conclusion: This study demonstrates the potential of a urine metabolite classifier that could be used to detect NRKI in pediatric kidney transplant patients, as well as non-invasively discriminate NRKI from rejection.
We are grateful for the participation of the children and their parents, and the support and dedication of the clinical team that have made this research possible.. Tom Blydt-Hansen received grant funding for this project by the Canadian Institutes of Health Research (CIHR) (grant 274755), the Manitoba Institute of Child Health, and the BC Children’s Hospital Research Institute..
 Mehrotra A, Rose C, Pannu N, Gill J, Tonelli M, Gill JS. Incidence and consequences of acute kidney injury in kidney transplant recipients. Am J Kidney Dis. 2012;59(4):558-565.
 Mammen C, Al Abbas A, Skippen P, Nadel H, Levine D, Collet JP, et al. Long-term risk of CKD in children surviving episodes of acute kidney injury in the intensive care unit: a prospective cohort study. Am J Kidney Dis. 2012;59(4):523-30.
 Askenazi DJ, Feig DI, Graham NM, Hui-Stickle S, Goldstein SL. 3-5 year longitudinal follow-up of pediatric patients after acute renal failure. Kidney Int. 2006;69(1):184-9.
 Bresolin N, Bianchini AP, Haas CA. Pediatric acute kidney injury assessed by pRIFLE as a prognostic factor in the intensive care unit. Pediatr Nephrol. 2013;28(3):485-92.
18:30 - 20:00
|Poster Session 1||Non-invasive differentiation of non-rejection kidney injury from acute rejection in pediatric renal transplant recipients||Exhibit-Poster Area|