Surveillance biopsies after paediatric kidney transplantation: A review

Detection of Subclinical Rejection in Pediatric Kidney Transplantation: Current and Future Practices

INTRODUCTION

The successes in the field of pediatric kidney transplantation over the past 60 years have been extraordinary. Year over year, there have been significant improvements in short-term graft survival. However, improvements in longer-term outcomes have been much less apparent. One important contributor has been the phenomenon of low-level rejection in the absence of clinical manifestations-so-called subclinical rejection (SCR).

METHODS

Traditionally, rejection has been diagnosed by changes in clinical parameters, including but not limited to serum creatinine and proteinuria. This review examines the shortcomings of this approach, the effects of SCR on kidney allograft outcome, the benefits and drawbacks of surveillance biopsies to identify SCR, and new urine and blood biomarkers that define the presence or absence of SCR.

RESULTS

Serum creatinine is an unreliable index of SCR. Surveillance biopsies are the method most utilized to detect SCR. However, these have significant drawbacks. New biomarkers show promise. These biomarkers include blood gene expression profiles and donor derived-cell free DNA; urine gene expression profiles; urinary cytokines, chemokines, and metabolomics; and other promising blood and urine tests.

CONCLUSION

Specific emphasis is placed on studies carried out in pediatric kidney transplant recipients.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT03719339.

Follow-up biopsies identify high rates of persistent rejection in pediatric kidney transplant recipients after treatment of T cell-mediated rejection

BACKGROUND

Incomplete resolution of T cell-mediated rejection (TCMR) after treatment may not be detected with serum creatinine monitoring and is associated with donor-specific antibodies and chronic rejection. We evaluate the utility of follow-up biopsies (FUB) to identify and characterize rates of persistent TCMR after treatment in pediatric kidney transplant patients.

METHODS

Patients from two pediatric transplant centers performing standard of care FUB at 1.5-2 months after treatment for TCMR were included. FUB were evaluated for extent of rejection resolution (complete vs. incomplete) and grade. Clinical data at time of FUB and later were reported, where available.

RESULTS

Fifty-eight patients underwent FUB, at mean of 1.7 months (SD 0.7) post-index biopsy. Rejection grade on index biopsy was Banff borderline (≥i1t1 and

CONCLUSIONS

FUB were effective at detecting persistent rejection, which was common among pediatric transplant patients after standard TCMR treatment. Until more effective rejection treatments or sensitive biomarkers are available, FUB may be effectively utilized to identify patients with ongoing rejection who would benefit from further treatment.

Collapse

Key Words

• biopsy
• pediatric
• rejection

Collapse

MESH Headings

• Humans
• Child
• Kidney Transplantation/adverse effects
• T-Lymphocytes
• Follow-Up Studies
• Biopsy
• Treatment Outcome
• Transplant Recipients
• Graft Rejection
• Kidney/pathology

Collapse

Grants

• R01 DK126807 NIDDK NIH HHS

Collapse

Affiliation(s)

Adina Landsberg Department of Medicine, University of Calgary, Calgary, AB, Canada
S. Sikandar Raza Department of Pediatrics, University of Alabama Heersink School of Medicine, Birmingham, AL, United States
Michael E. Seifert Department of Pediatrics, University of Alabama Heersink School of Medicine, Birmingham, AL, United States
Tom D. Blydt-Hansen BC Children’s Hospital, Division of Nephrology, Department of Pediatrics, University of British Columbia, Vancouver, BC, Canada

Collapse

Early surveillance biopsy utilization and management of pediatric renal allograft acute T cell-mediated rejection in Canadian centers: Observations from the PROBE multicenter cohort study

BACKGROUND

Early TCMR surveillance with protocol kidney biopsy is used differentially among pediatric kidney transplant centers. Little has been reported about actual center-based differences, and this variability may influence TCMR ascertainment, treatment, and monitoring more broadly.

METHODS

Data from the PROBE multicenter study were used to identify patients from centers conducting ESB or LSIB. ESB was defined as >50% of patients having at least 1 surveillance biopsy in the first 9 months. Patients were compared for number of biopsies, rejection episodes, treatment, and follow-up monitoring.

RESULTS

A total of 261 biopsies were performed on 97 patients over 1-2 years of follow-up. A total of 228 (87%) of biopsies were performed in ESB centers. Compared to LSIB centers, ESB centers had 7-fold more episodes of TCMR diagnosed on any biopsy [0.8 ± 1.2 vs 0.1 ± 0.4; P < .001] and a 3-fold higher rate from indication biopsies [0.3 ± 0.9 vs 0.1 ± 0.3; P = .04]. The proportion of rejection treatment varied based on severity: Banff borderline i1t1 (40%);>i1t1 and < Banff 1A (86%); and ≥ Banff 1A (100%). Biopsies for follow-up were performed after treatment in 80% of cases (n = 28) of rejection almost exclusively at ESB centers, with 17 (61%) showing persistence of TCMR (≥i1t1).

CONCLUSIONS

Practice variation exists across Canadian pediatric renal transplant centers with ESB centers identifying more episodes of rejection. Additionally, treatment of Banff borderline is not universal and varies with severity regardless of center type. Lastly, follow-up biopsies are performed inconsistently and invariably show persistence of rejection.

Yield and utility of surveillance kidney biopsies in pediatric kidney transplant recipients at various time points post-transplant

BACKGROUND

Due to a lack of consensus on SB for pediatric kidney transplant recipients, we evaluated the yield and clinical utility of SB findings at various time points post-transplant.

METHODS

Patients transplanted at a single institution between 2014 and 2020 with at least one SB at 1.5, 3, 6, 12, and 24 months post-transplant were included. Additional biopsies were done for indication (IB). TCMR was classified by Banff criteria (score ≥i1t1).

RESULTS

Forty-seven patients had 142 biopsies (SB = 113, IB = 29); 19 (40.4%) of whom experienced at least one TCMR episode in the first-year post-transplant. The greatest SB yield of any pathologic abnormality was at 6 months (57.1%; P < .001). Six months also had the highest yield for TCMR (42.9%), compared with 3.3%, 20.8%, 15.0%, and 9.1% at 1.5, 3, 12 months, and 24 months, respectively (P = .003). SB instigated intensification of immunosuppression (28.3% cases), reduction of immunosuppression (2.7% cases), and other non-immunosuppressant changes (1.8% cases). The 6-month SB led to the greatest number of changes in management (53.6%), compared with 1.5, 3, 12, and 24 months (13.3, 20.8, 25.0, and 36.4%, respectively; P = .012). There were no major biopsy-related complications.

CONCLUSIONS

SBs identify an important burden of subclinical rejection and other pathology leading to changes in clinical management. The greatest yield was at 6 months, whereas the least utility was at the 1.5 months. Selection of SB timing may be tailored such that the optimal yield is balanced against the procedural risk.

Donor-derived cell-free DNA (dd-cfDNA) for detection of allograft rejection in pediatric kidney transplants

In pediatric transplantation, acute rejection is a major contributor of graft failure. Current approaches include kidney biopsy in response to graft dysfunction and/or the emergence of donor-specific HLA antibodies (DSA). However, biopsy is associated with potential complications. Thus, there is a need for non-invasive diagnostics. Detection of donor-derived cell-free DNA (dd-cfDNA, AlloSure) > 1% is associated with rejection in adult kidney transplants. Here, we evaluate the utility of dd-cfDNA for identifying allograft rejection in pediatric patients. Between 10/2017 and 10/2019, 67 patients, who underwent initial testing with dd-cfDNA as part of routine monitoring or in response to clinical suspicion for rejection, were included. Biopsies were performed when dd-cfDNA > 1.0% or where clinical suspicion was high. Demographics, dd-cfDNA, antibody status, and biopsies were collected prospectively. Data were analyzed to determine predictive value of dd-cfDNA for identifying grafts at risk for rejection. 19 of 67 patients had dd-cfDNA testing as part of routine monitoring with a median dd-cfDNA score of 0.37 (IQR: 0.19-1.10). 48 of 67 patients who had clinical suspicion of rejection had median dd-cfDNA score of 0.47 (0.24-2.15). DSA-positive recipients had higher dd-cfDNA scores than those who were negative or had AT1R positivity alone (P = .003). There was no association between dd-cfDNA score and strength of DSA positivity. 7 of 48 recipients had a biopsy with a dd-cfDNA score <1%; two showed evidence of rejection. Neither DSA nor AT1R positivity was statistically associated with biopsy-proven rejection. However, dd-cfDNA >1% was diagnostic of rejection with sensitivity of 86% and specificity of 100% (AUC: 0.996, 0.98-1.00; P = .002). dd-cfDNA represents a non-invasive method for early detection of rejection in pediatric renal transplants. Our study shows dd-cfDNA to be highly predictive of histological rejection and superior to other indicators such as graft dysfunction or antibody positivity alone. Further studies are necessary to refine these initial observations.

Characterizing the frequency of modifiable histological changes observed on surveillance biopsies in pediatric kidney allograft recipients

BACKGROUND

Rejection is responsible for just under 50% of graft loss in the pediatric kidney transplant population. Early identification and treatment of allograft injury, specifically modifiable pathologies such as subclinical rejection (SCR), calcineurin inhibitor toxicity, and BK virus nephropathy, may improve allograft survival. Protocol surveillance biopsy (SB) currently offers the earliest opportunity for targeted interventions.

METHODS

This is a single-center retrospective review of 215 kidney SBs obtained from 2008 to 2016 in 97 pediatric kidney transplant recipients. SBs were obtained at 6, 12, and 24 months post-transplantation. Frequency of abnormal histologic findings, estimated glomerular filtration rate at time of SB, and SB-related complications were recorded. Data were analyzed to investigate possible time trends and the presence of demographic or clinical associations with abnormal histologic findings.

RESULTS

Potentially modifiable histologic findings were seen in 38.1% of all SBs. SCR was found with increasing frequency across all time points with an estimated 49% increase in the odds of a SCR finding per additional 6 months post-transplantation (aOR 1.49, 95% CI 1.06-2.09, p = 0.022). Among follow-up biopsies in patients who underwent treatment for SCR, 50% had no SCR and 18.8% showed histologic improvement. The complication rate associated with SB was 1.9% (4/215 SBs) and consisted of only minor complications.

CONCLUSIONS

SBs are safe and offer the opportunity to identify and treat modifiable histologic changes in the pediatric kidney transplant population. The performance of SBs for up to 2 years after transplantation can have meaningful clinical impact.

Pediatric kidney transplantation in Egypt: Results of 10-year single-center experience

Pediatric kidney transplantation is a multidisciplinary therapy that needs special consideration and experience. In this study, we aimed to present CUCH experience; over a 10-year period, as a specialized center of kidney transplantation in children. We studied 148 transplantations performed at a single center from 2009 to 2018. Pretransplant and follow-up data were collected and graft/patient survival rates were evaluated. A total of 48 patients developed at least one rejection episode during 688 patient-years of follow-up. Infections, recurrence of original disease, and malignancy were the most important encountered medical complications (20%, 2%, and 1.4%, respectively). One-year patient survival was 94.1%, while graft and patient survival was 91.9%. Graft/patient survival at 5, 7, and 9 years was 90%, 77%, and 58%, respectively. Infections were the main cause (69%) of mortality. Death with a functioning graft and CR were the main causes of graft loss (48% and 33%, respectively). Pediatric kidney transplantation in Egypt is still a challenging yet successful experience. Rejections and infections are the most frequent complications. Short-term outcomes surpass long-term ones and graft survival rates are similar to the international standard.

Pediatric Kidney Transplantation in Perú: A Single-Center Initial Experience

BACKGROUND

Pediatric kidney transplantation (PKTx) is the preferred therapy for children with end-stage renal disease (ESRD) worldwide. Regrettably, in Perú, access to PKTx is extremely difficult due to recipient/donor socio-economic status, health care structure and especially, scarcity of organs. Our center (the only pediatric institute in the country) has recently started a PKTx program with good midterm results. The aim of this study was to present our outcomes.

METHODS

Retrospective analysis of prospectively collected data between December 2017 and August 2019. Fourteen PKTx (< 18 years old) were achieved. As per our protocol: pre-implantation/protocol biopsies, antibody assessment (T/B cell flow cytometric plus HLA testing applying polymerase chain reaction-based technology), triple immunosuppression (tacrolimus, mycophenolate mofetil, steroids) and induction therapy was performed in every case.

RESULTS

The recipient's mean age at the time of PKTx was 14.14 ± 2.62, 8/14 (57.14%) were male, 50% developed ESRD due to undetermined etiology, 11/14 (78.57%) received a deceased donor allograft, and 9/14 (64.28%) required induction with thymoglobulin. Postoperative complications included: delayed graft function (1/14, 7.14%), 1 (7.14%) developed gross hematuria associated with allograft disfunction post-protocol allograft biopsy that was managed conservatively and 1 recipient (7.14%) developed grade II oligoastrocytoma, at 10 months post PKTx.

CONCLUSIONS

PKTx is the best therapeutic option for children with ESRD. Our group demonstrated that even in countries with limited resources like Perú, good midterm results can be achieved. Emphasis should be given to improve access to transplantation especially in the setting of pediatric recipients.

Benefits and risks of protocol biopsies in pediatric renal transplantation

Protocol biopsies are defined as sampling of allograft tissue at predetermined times regardless of function. This procedure can be justified due to the lack of non-invasive methods to reliably diagnose rejection (acute or subclinical). Changes in creatinine are not seen with subclinical rejection or early acute rejection and do not always correlate with efficacy of treatment. Parents and providers are still hesitant to pursue protocol biopsy due to the potential complications and lack of definitive evidence of a benefit from doing this procedure. Importantly, the rate of transplant renal biopsy complications requiring additional intervention is low. It is unclear if detection and treatment of subclinical rejection detected on protocol biopsy will lead to improved graft survival. Our goal is to review the literature on this topic and share some of the experience in our center. Definition, indications, and complications of diagnostic transplant renal biopsies are not included in this review.

Protocol biopsies in pediatric renal transplantation: a precious tool for clinical management

BACKGROUND

Kidney transplantation is the best treatment for children with end-stage kidney disease. Early results have improved, but late graft loss is still a major problem. Non-invasive, fully reliable early biomarkers of acute rejection are currently missing.

METHODS

Our aim was to evaluate the efficacy of protocol biopsies (PBXs) in a pediatric population. During 11 years, 209 renal transplantations were performed in 204 pediatric patients. Biopsies were performed 3-6 months, 1 year, and 5 years after transplantation. Procedure-related complications were systematically looked for by means of ultrasound scans.

RESULTS

Unexpected findings (mainly subclinical rejections) requiring therapeutic intervention were found in 19.3% biopsies performed at 3-6 months, in 18.4% in 12-month biopsies and in none of those performed after 5 years. The 13.6% patients at 12-month biopsies and 23.6% at 5-year biopsies showed calcineurin inhibitor (CNI) toxicity. Interstitial fibrosis and tubular atrophy (IF/TA) was found in 17.6 and 83.6% of patients at 12-month and 5-year biopsies, respectively. Complications of the PBX were infrequent. Five-year estimated glomerular filtration rate (GFR) was not significantly different in patients who received treatment for any cause and patients with normal histology.

CONCLUSIONS

Although we do not have a control group, we may speculate that patients who received treatment returned to a "standard" condition possibly improving final outcome. Protocol biopsies are a powerful diagnostic tool for the management of pediatric renal transplant recipients. In view of the lack of evidence that biopsies taken 5 years after transplantation lead to any therapeutic change, their use should be reconsidered.

Relationship between cytotoxic T-lymphocyte antigen 4 -318C/T (rs5742909) gene polymorphism and the risk of acute rejection in renal transplantation

Results on the relationship between CTLA4 -318C/T (rs5742909) gene polymorphism and risk of acute rejection in renal transplantation are still conflicting. This meta-analysis was performed to update the association between CTLA4 -318C/T and risk of acute rejection in renal transplantation. The association investigations were identified from PubMed and Cochrane Library, and eligible studies were included and synthesized using meta-analysis method. Twelve reports were included in this meta-analysis for the association of CTLA4 -318C/T gene polymorphism with acute rejection risk in renal transplantation, consisting of 728 acute rejection patients and 1628 non-acute rejection controls. The association between CTLA4 -318C/T gene polymorphism and acute rejection risk in renal transplantation for overall populations was not found in this meta-analysis (T allele: OR=0.96, 95% CI: 0.60-1.54, P=.88; TT genotype: OR=0.90, 95% CI: 0.47-1.71, P=.74; CC genotype: OR=1.00, 95% CI: 0.62-1.59, P=.98). Interestingly, T allele was associated with the risk of acute rejection in renal transplantation in African population. In conclusion, CTLA4 -318C/T gene polymorphism is not associated with the risk of acute rejection in renal transplantation in overall populations.