Early subclinical rejection treated with low dose i.v. steroids is not associated to graft survival impairment: 13-years’ experience at a single center

The Value of Protocol Biopsy in Kidney Transplantation on Monitoring Transplant Outcomes: A Systematic Review and Meta-Analysis

BACKGROUND

There is a great debate about the role of biopsies per protocol in kidney transplant recipients, and the published studies show contradictory results. We aimed to assess the safety and effectiveness of protocol biopsies in kidney transplant recipients in improving short- and long-term outcomes.

METHODS

We conducted searches until July of 2023 to identify all randomized clinical trials (RCT). Studies were identified through search strategies for CENTRAL, MEDLINE, EMBASE, and LILACS. Titles and abstracts were screened independently by 2 authors; 2 authors independently assessed retrieved abstracts and the full text. Assessment of risk of bias was carried out using the Cochrane risk of bias tool. The outcomes of interest were: Acute rejection, graft loss, mortality, glomerular filtration rate, and safety outcomes. Meta-analysis was performed for variables of interest when appropriate. Quality of evidence was assessed using GRADE methodology.

RESULTS

We screened 5,695 records. Four trials met all eligibility criteria. No benefit of protocol biopsy was found in detecting acute rejection (3 studies RR: 2.0, 95% CI: 0.68-5.85, p = .2) or preventing graft loss at 12 months (2 studies, RR 0.33, 95% CI 0.06-1.72, p = .19). No differences were found between the groups in the glomerular filtration rate at 6 months post-transplantation (2 studies, MD 2.97, 95% CI 1.4-7.3, p = .18). A total of 23 safety events were present in the biopsy group compared to six in the control group.

CONCLUSION

No benefit was found in performing protocol biopsy following kidney transplantation.

Optimizing the approach to monitoring allograft inflammation using serial urinary CXCL10/creatinine testing in pediatric kidney transplant recipients

BACKGROUND

Urinary CXCL10/creatinine (uCXCL10/Cr) is proposed as an effective biomarker of subclinical rejection in pediatric kidney transplant recipients. This study objective was to model implementation in the clinical setting.

METHODS

Banked urine samples at a single center were tested for uCXCL10/Cr to validate published thresholds for rejection diagnosis (>80% specificity). The positive predictive value (PPV) for rejection diagnosis for uCXCL10/Cr-indicated biopsy was modeled with first-positive versus two-test-positive approaches, with accounting for changes associated with urinary tract infection (UTI), BK and CMV viremia, and subsequent recovery.

RESULTS

Seventy patients aged 10.5 ± 5.6 years at transplant (60% male) had n = 726 urine samples with n = 236 associated biopsies (no rejection = 167, borderline = 51, and Banff 1A = 18). A threshold of 12 ng/mmol was validated for Banff 1A versus no-rejection diagnosis (AUC = 0.74, 95% CI = 0.57-0.92). The first-positive test approach (n = 69) did not resolve a clinical diagnosis in 38 cases (55%), whereas the two-test approach resolved a clinical diagnosis in the majority as BK (n = 17/60, 28%), CMV (n = 4/60, 7%), UTI (n = 8/60, 13%), clinical rejection (n = 5/60, 8%), and transient elevation (n = 18, 30%). In those without a resolved clinical diagnosis, PPV from biopsy for subclinical rejection is 24% and 71% (p = .017), for first-test versus two-test models, respectively. After rejection treatment, uCXCL10/Cr level changes were all concordant with change in it-score. Sustained uCXCL10/Cr after CMV and BK viremia resolution was associated with later acute rejection.

CONCLUSIONS

Urinary CXCL10/Cr reliably identifies kidney allograft inflammation. These data support a two-test approach to reliably exclude other clinically identifiable sources of inflammation, for kidney biopsy indication to rule out subclinical rejection.

Prediction of very early subclinical rejection with machine learning in kidney transplantation

Protocol biopsy is a reliable method for assessing allografts status after kidney transplantation (KT). However, due to the risk of complications, it is necessary to establish indications and selectively perform protocol biopsies by classifying the high-risk group for early subclinical rejection (SCR). Therefore, the purpose of this study is to analyze the incidence and risk factors of early SCR (within 2 weeks) and develop a prediction model using machine learning. Patients who underwent KT at Samsung Medical Center from January 2005 to December 2020 were investigated. The incidence of SCR was investigated and risk factors were analyzed. For the development of prediction model, machine learning methods (random forest, elastic net, extreme gradient boosting [XGB]) and logistic regression were used and the performance between the models was evaluated. The cohorts of 987 patients were reviewed and analyzed. The incidence of SCR was 14.6%. Borderline cellular rejection (BCR) was the most common type of rejection, accounting for 61.8% of cases. In the analysis of risk factors, recipient age (OR 0.98, p = 0.03), donor BMI (OR 1.07, p = 0.02), ABO incompatibility (OR 0.15, p < 0.001), HLA II mismatch (two [OR 6.44, p < 0.001]), and ATG induction (OR 0.41, p < 0.001) were associated with SCR in the multivariate analysis. The logistic regression prediction model (average AUC = 0.717) and the elastic net model (average AUC = 0.712) demonstrated good performance. HLA II mismatch and induction type were consistently identified as important variables in all models. The odds ratio analysis of the logistic prediction model revealed that HLA II mismatch (OR 6.77) was a risk factor for SCR, while ATG induction (OR 0.37) was a favorable factor. Early SCR was associated with HLA II mismatches and induction agent and prediction model using machine learning demonstrates the potential to predict SCR.

The Protective Role of Protocol Biopsy for Allograft Kidney Maintenance in Kidney Transplantation

Many studies have reported that protocol biopsy (PB) may help preserve kidney function in kidney transplant recipients. Early detection and treatment of subclinical rejection may reduce the incidence of chronic antibody-mediated rejection and graft failure. However, no consensus has been reached regarding PB effectiveness, timing, and policy. This study aimed to evaluate the protective role of routine PB performed 2 weeks and 1 year after kidney transplantation. We reviewed 854 kidney transplant recipients at the Samsung Medical Center between July 2007 and August 2017, with PBs planned at 2 weeks and 1 year after transplantation. We compared the trends in graft function, chronic kidney disease (CKD) progression, new-onset CKD, infection, and patient and graft survival between the 504 patients who underwent PB and 350 who did not undergo PB. The PB group was again divided into 2 groups: the single PB group (n = 207) and the double PB group (n = 297). The PB group was significantly different from the no-PB group in terms of the trends in graft function (estimated glomerular filtration rate). The Kaplan-Meier curve showed that PB did not significantly improve graft or overall patient survival. However, in the multivariate Cox analysis, the double PB group had advantages in graft survival, CKD progression, and new-onset CKD. PB can play a protective role in the maintenance of kidney grafts in kidney transplant recipients.

Effects of antirejection therapies for early subclinical acute rejection in renal transplant protocol biopsies

Background

Although recently strengthened immunosuppression protocols have decreased the incidence of clinical acute rejection of renal transplants, subclinical acute rejection and borderline changes remain problematic. This study was performed to evaluate the effects of antirejection therapies for early subclinical acute rejection and borderline changes.

Methods

In total, 269 renal transplant patients who received 3-month and 1-year protocol biopsies after renal transplantation were enrolled this study and divided into those with normal findings (Group A) and those with ≥ borderline changes (Group B) according to the 3-month pathological results. Pathological changes, graft function, and graft survival were evaluated at 1 year.

Results

The 3-month protocol biopsy revealed normal findings in 166 patients (Group A) and borderline changes and subclinical acute rejection in 103 patients (Group B). In Group A, 65.1% (n = 108) of the patients maintained normal findings at 1 year, while 30.1% (n = 50) deteriorated to ≥ borderline changes. In Group B, 52.4% (n = 54) of patients improved to normal. Among patients with subclinical acute rejection, 25.0% (n = 5) maintained subclinical acute rejection at 1 year despite antirejection therapy. The mean estimated glomerular filtration rate decreased from 60.4 ± 24.5 to 58.3 ± 19.0 mL/min/1.73 m2 in Group A and from 57.2 ± 28.2 to 53.7 ± 20.3 mL/min/1.73 m2 in Group B (p = 0.417). The 3-, 5-, and 7-year graft survival rates were 99.4%, 99.4%, and 97.6% in Group A and 100.0%, 98.6%, and 98.6% in Group B, respectively (p = 0.709).

Conclusions

Subclinical acute rejection is likely to recur. However, intervention for subclinical acute rejection in the early period after transplantation may help to prevent subsequent histological changes.

Clinical Significance of Renal Allograft Protocol Biopsies: A Single Tertiary Center Experience in Malaysia

Background

The role of protocol renal allograft biopsy in kidney transplantation is controversial due to the concern with procedural-related complications; however, its role is slowly evolving. Recent evidence suggests that protocol biopsy is useful in detecting subclinical renal pathology. Early recognition and treatment of renal pathologies can improve long-term outcomes of renal allografts.

Methodology

A total of 362 renal allograft protocol biopsies were performed in adult recipients of kidney transplantation between 2012 and 2017. After excluding those with poor quality or those performed with a baseline serum creatinine level >200 umol/L, we analyzed 334 (92.3%) biopsies. Histology reports were reviewed and categorized into histoimmunological and nonimmunological changes. The immunological changes were subcategorized into the following: (1) no acute rejection (NR), (2) borderline changes (BC), and (3) subclinical rejection (SCR). Nonimmunological changes were subcategorized into the following: (1) chronicity including interstitial fibrosis/tubular atrophy (IFTA), chronic T-cell-mediated rejection (TCMR), unspecified chronic lesions, and arterionephrosclerosis, (2) de novo glomerulopathy/recurrence of primary disease (RP), and (3) other clinically unsuspected lesions (acute pyelonephritis, calcineurin inhibitors toxicity, postinfective glomerulonephritis, and BK virus nephropathy). Risk factors associated with SCR were assessed.

Results

For the histoimmunological changes, 161 (48.2%) showed NR, 145 (43.4%) were BC, and 28 (8.4%) were SCR. These clinical events were more pronounced for the first 5 years; our data showed BC accounted for 59 (36.4%), 64 (54.2%), and 22 (40.7%) biopsies within <1 year, 1-5 years, and > 5 years, respectively (p = 0.011). Meanwhile, the incidence for SCR was 6 (3.7%) biopsies in <1 year, 18 (15.3%) in 1-5 years, and 4 (7.4%) in >5 years after transplantation (p=0.003). For the nonimmunological changes, chronicity, de novo glomerulopathy/RP, and other clinically unsuspected lesions were seen in 40 (12%), 10 (3%), and 12 (3.6%) biopsies, respectively. Living-related donor recipients were associated with decreased SCR (p=0.007).

Conclusions

Despite having a stable renal function, our transplant recipients had a significant number of subclinical rejection on renal allograft biopsies.

Long-term effects of delayed graft function duration on function and survival of deceased donor kidney transplants

Introduction:

Delayed graft function (DGF) is a frequent complication after deceased donor kidney transplantation with an impact on the prognosis of the transplant. Despite this, long-term impact of DGF on graft function after deceased donor kidney transplantation has not been properly evaluated.

Objective:

The main objective of this study was to evaluate risk factors for DGF and the impact of its occurrence and length on graft survival and function.

Methods:

A retrospective cohort study was performed in 517 kidney transplant recipients who received a deceased donor organ between January 2008 and December 2013.

Results:

The incidence of DGF was 69.3% and it was independently associated with donor's final serum creatinine and age, cold ischemia time, use of antibody induction therapy and recipient's diabetes mellitus. The occurrence of DGF was also associated with a higher incidence of Banff ≥ 1A grade acute rejection (P = 0.017), lower graft function up to six years after transplantation and lower death-censored graft survival at 1 and 5 years (P < 0.05). DGF period longer than 14 days was associated with higher incidence of death-censored graft loss (P = 0.038) and poorer graft function (P < 0.001). No differences were found in patient survival.

Conclusions:

The occurrence of DGF has a long-lasting detrimental impact on graft function and survival and this impact is even more pronounced when DGF lasts longer than two weeks.

Transplantomics: Toward Precision Medicine in Transplantation Research

Precision medicine is an emerging integrative approach for disease prevention, early detection, and treatment which takes into account individual variability in genetic and other molecular measurements, medical history, environmental exposures, and lifestyle. The development and availability of genomic and other molecular profiling technologies provide an unprecedented opportunity to apply precision medicine strategies in transplantation research. Developing integrative computational methods to analyze these diverse types of data provides new opportunities to impact diagnostics and therapeutics. In this article, we discuss ways we can leverage molecular data sets to develop new hypotheses for disease mechanisms, identify new disease biomarkers, and reposition drugs for diseases with unmet needs. We specifically discuss computational methods that can be applied to achieve these goals in the context of organ transplant.

Subclinical Rejection in Renal Transplantation: Reappraised

Short-term outcomes in renal transplantation have improved significantly in the past few years. However, the improvement in long-term outcomes has been modest. The reasons for graft failure beyond the first year of transplantation have been attributed to several different factors. We believe that subclinical rejection (SCR) may be 1 of the factors that contribute to graft loss in the long run. We also believe that there are data to suggest that SCR leads to progressive fibrosis and loss of graft function. This has been demonstrated even in patients who have mild degrees of subclinical inflammation. This review outlines the major studies that have been published on this important topic. It also outlines potential risk factors for the development of SCR. The current approach and diagnostic methods are discussed as well as their pros and cons. Newer noninvasive methods of diagnosis as well as molecular diagnostics and their merits and shortcomings are also discussed in some depth. Thus, the proposed state of the art review on SCR will create a renewed interest at all levels including transplant clinicians, transplant researchers, pharmaceutical industries as well as regulatory organizations.

Non-invasive approaches in the diagnosis of acute rejection in kidney transplant recipients, part II: omics analyses of urine and blood samples

Kidney transplantation (KTx) represents the best available treatment for patients with end-stage renal disease. Still, the full benefits of KTx are undermined by acute rejection (AR). The diagnosis of AR ultimately relies on transplant needle biopsy. However, such an invasive procedure is associated with a significant risk of complications and is limited by sampling error and interobserver variability. In the present review, we summarize the current literature about non-invasive approaches for the diagnosis of AR in kidney transplant recipients (KTRs), including in vivo imaging, gene-expression profiling and omics analyses of blood and urine samples. Most imaging techniques, such as contrast-enhanced ultrasound and magnetic resonance, exploit the fact that blood flow is significantly lowered in case of AR-induced inflammation. In addition, AR-associated recruitment of activated leucocytes may be detectable by 18F-fluorodeoxyglucose positron emission tomography. In parallel, urine biomarkers, including CXCL9/CXCL10 or a three-gene signature of CD3ε, CXCL10 and 18S RNA levels, have been identified. None of these approaches has yet been adopted in the clinical follow-up of KTRs, but standardization of analysis procedures may help assess reproducibility and comparative diagnostic yield in large, prospective, multicentre trials.