Protocol Transplant Biopsies in Kidney Allografts: Why and When Are They Indicated?: Table 1

Approach to Kidney Allograft Dysfunction: A Brief Review

It is important for providers caring for kidney transplant recipients to be familiar with the common causes of allograft dysfunction. Early detection of allograft dysfunction leads to timely management, with the goal of preventing or delaying progression to allograft failure. Although transplant rejection is always a concern, the differential diagnoses for allograft dysfunction are broad and include perioperative complications, infections, recurrent disease, and calcineurin nephrotoxicity. In this review, we will go over early and late causes of allograft dysfunction and discuss the basic workup and principles of management for each condition.

Interpretation of LDH Values after Kidney Transplantation

Kidney transplantation is the gold-standard therapy for end-stage renal disease. However, in the early postoperative period following allograft kidney transplantation, insufficient graft function presents a diagnostic challenge to clinicians. Ischemic damage to the graft and/or an early autoimmune rejection may cause a decrease in function. Ischemic damage is a benign and transient condition, while acute immune rejection requires immediate therapy. A kidney graft ultrasound may produce a false negative result, and graft biopsy is invasive and slow to return results. Serum lactate dehydrogenase (LDH) is under examination as a possible tool for differential diagnosis between ischemic damage and immune rejection. Herein, we analyze the continuous lab results of four patients in the early post-transplantation period, showing patterns correlating with different clinical outcomes and prognoses. In our experience, a persistent elevated LDH accompanies ischemic damage. Immune rejection was, however, associated with a decrease in LDH. Hemodialysis was not a confounding factor, while packed red blood cell transfusion caused severe diagnostic problems.

Revisiting transplant immunology through the lens of single-cell technologies

Solid organ transplantation (SOT) is the standard of care for end-stage organ disease. The most frequent complication of SOT involves allograft rejection, which may occur via T cell- and/or antibody-mediated mechanisms. Diagnosis of rejection in the clinical setting requires an invasive biopsy as there are currently no reliable biomarkers to detect rejection episodes. Likewise, it is virtually impossible to identify patients who exhibit operational tolerance and may be candidates for reduced or complete withdrawal of immunosuppression. Emerging single-cell technologies, including cytometry by time-of-flight (CyTOF), imaging mass cytometry, and single-cell RNA sequencing, represent a new opportunity for deep characterization of pathogenic immune populations involved in both allograft rejection and tolerance in clinical samples. These techniques enable examination of both individual cellular phenotypes and cell-to-cell interactions, ultimately providing new insights into the complex pathophysiology of allograft rejection. However, working with these large, highly dimensional datasets requires expertise in advanced data processing and analysis using computational biology techniques. Machine learning algorithms represent an optimal strategy to analyze and create predictive models using these complex datasets and will likely be essential for future clinical application of patient level results based on single-cell data. Herein, we review the existing literature on single-cell techniques in the context of SOT.

Dynamics of Donor-Derived Cell-Free DNA at the Early Phase After Pediatric Kidney Transplantation: A Prospective Cohort Study

Background: Donor-derived cell-free DNA (ddcfDNA) has been suggested as an indicator of allograft injury in adult and pediatric kidney transplantation (KTx). However, the dynamics of ddcfDNA in pediatric KTx have not been investigated. In addition, it has not been demonstrated whether donor-recipient (D/R) size mismatch affect ddcfDNA level.

Methods: Pediatric KTx recipients with a single donor kidney were enrolled and followed up for 1 year. ddcfDNA, calculated as a fraction (%) in the recipient plasma, was examined longitudinally within 3 months post-transplant. D/R size mismatch degree was described as D/R height ratio. The 33rd percentile of D/R height ratio (0.70) was used as the cut-off to divide the patients into low donor-recipient height ratio group (<0.70) and high donor-recipient height ratio group (≥0.70). The dynamics of ddcfDNA were analyzed and the impact factors were explored. Stable ddcfDNA was defined as the first lowest ddcfDNA. ddcfDNA flare-up was defined as a remarkable elevation by a proportion of >30% from stable value with a peak value >1% during elevation.

Results: Twenty-one clinically stable recipients were enrolled. The median D/R height ratio was 0.83 (0.62–0.88). It took a median of 8 days for ddcfDNA to drop from day 1 and reach a stable value of 0.67% (0.46–0.73%). Nevertheless, 61.5% patients presented ddcfDNA>1% at day 30. Besides, 81.0% (17/21) of patients experienced elevated ddcfDNA and 47.6% (10/21) met the standard of ddcfDNA flare-up. Donor-recipient height ratio was an independent risk factor for ddcfDNA flare-up (odds ratio = 0.469 per 0.1, 95% CI 0.237–0.925, p = 0.029) and low donor-recipient height ratio (<0.70) was found to increase the risk of flare-up occurrence (odds ratio = 15.00, 95% CI 1.342–167.638, p = 0.028).

Conclusions: ddcfDNA rebounds in many stable pediatric KTx recipients without rejection. This may be induced by significant D/R size mismatch and may affect its diagnostic performance at the early phase after pediatric KTx in children.

Donor-derived cell-free DNA and renal allograft rejection in surveillance biopsies and indication biopsies

To evaluate the role of circulating dd-cfDNA in allograft surveillance in immunologically high-risk patients, a retrospective cross-sectional study of 261 kidney transplant recipients who underwent outpatient allograft biopsy at our center between September 2020 and August 2021 was performed. Of the 236 dd-cfDNA results included, 37 samples were obtained at the time of a surveillance biopsy in sensitized recipients and 199 at the time of a clinically indicated biopsy. The median serum creatinine at the time of the biopsy was 1.3 mg/dl and 2.1 mg/dl for surveillance biopsies and clinically indicated biopsies, respectively (p<0.001). Rejection was diagnosed in 27% of surveillance biopsies and 29% of clinically indicated biopsies. Among surveillance biopsies, sensitivity and specificity to detect rejection were 0% and 89%, respectively, and among clinically indicated biopsies they were 28% and 96%, respectively. The sensitivity and specificity to detect antibody-mediated rejection were 0% and 91% among surveillance biopsies and 50% and 94% among clinically indicated biopsies. Nine biopsies without rejection findings had corresponding dd-cfDNA of ≥1%. Our data does not support dd-cfDNA as a biomarker for kidney allograft rejection, even in immunologically high-risk patients in the absence of graft dysfunction. This article is protected by copyright. All rights reserved.

A joint transition model for evaluating eGFR as biomarker for rejection after kidney transplantation

The estimated glomerular filtration rate (eGFR) quantifies kidney graft function and is measured repeatedly after transplantation. Kidney graft rejection is diagnosed by performing biopsies on a regular basis (protocol biopsies at time of stable eGFR) or by performing biopsies due to clinical cause (indication biopsies at time of declining eGFR). The diagnostic value of the eGFR evolution as biomarker for rejection is not well established. To this end, we built a joint model which combines characteristics of transition models and shared parameter models to carry over information from one biopsy to the next, taking into account the longitudinal information of eGFR collected in between. From our model, applied to data of University Hospitals Leuven (870 transplantations, 2 635 biopsies), we conclude that a negative deviation from the mean eGFR slope increases the probability of rejection in indication biopsies, but that, on top of the biopsy history, there is little benefit in using the eGFR profile for diagnosing rejection. Methodologically, our model fills a gap in the biomarker literature by relating a frequently (repeatedly) measured continuous outcome with a less frequently (repeatedly) measured binary indicator. The developed joint transition model is flexible and applicable to multiple other research settings.

Automated detection algorithm for C4d immunostaining showed comparable diagnostic performance to pathologists in renal allograft biopsy

A deep learning-based image analysis could improve diagnostic accuracy and efficiency in pathology work. Recently, we proposed a deep learning-based detection algorithm for C4d immunostaining in renal allografts. The objective of this study is to assess the diagnostic performance of the algorithm by comparing pathologists' diagnoses and analyzing the associations of the algorithm with clinical data. C4d immunostaining slides of renal allografts were obtained from two different institutions (100 slides from the Asan Medical Center and 86 slides from the Seoul National University Hospital) and scanned using two different slide scanners. Three pathologists and the algorithm independently evaluated each slide according to the Banff 2017 criteria. Subsequently, they jointly reviewed the results for consensus scoring. The result of the algorithm was compared with that of each pathologist and the consensus diagnosis. Clinicopathological associations of the results of the algorithm with allograft survival, histologic evidence of microvascular inflammation, and serologic results for donor-specific antibodies were also analyzed. As a result, the reproducibility between the pathologists was fair to moderate (kappa 0.36-0.54), which is comparable to that between the algorithm and each pathologist (kappa 0.34-0.51). The C4d scores predicted by the algorithm achieved substantial concordance with the consensus diagnosis (kappa = 0.61), and they were significantly associated with remarkable microvascular inflammation (P = 0.001), higher detection rate of donor-specific antibody (P = 0.003), and shorter graft survival (P < 0.001). In conclusion, the deep learning-based C4d detection algorithm showed a diagnostic performance similar to that of the pathologists.

Complications and Risks of Percutaneous Renal Biopsy

BACKGROUND

Renal biopsy performed in native and transplant kidneys is generally considered a safe procedure.

AIM

In this study, we evaluated renal biopsy complications and risk factors in one nephrology facility.

MATERIAL AND METHODS

We conducted a three-year retrospective study on patients who underwent renal biopsy between January 2014 and December 2016. Strict written biopsy protocol was followed. Clinical and laboratory data were obtained from medical charts. Complications were categorised as minor and major, according to the need for intervention. Minor complications included macrohematuria and/or hematoma that did not require intervention. Major complications included hematuria or hematoma with fall of hematocrit that required a blood transfusion, surgery or caused death. A binary logistic regression model was used to analyse the possible factors associated with complications after the biopsy.

RESULTS

We analysed 345 biopsies; samples were taken from patients aged from 15-81 years, of whom 61% were men. A total of 21 (6%) patients developed a complication, 4.4% minor and 1.7% major complications. There were no nephrectomy or death due to biopsy intervention. Overweight patients, as well as those with higher creatinine, lower hemoglobin, higher blood pressure and biopsy due to AKI had higher chances to develop complications (p = 0.037, p = 0.023, p = 0.032, p = 0.002, p = 0.002, respectively). The patients' age, gender, kidney dimension, number of passes and uninterrupted aspirin therapy were not found as significant predictors of complications. In the multivariate logistic model, body weight (OR = 1.031, 95%CI = 1.002-1.062), lower hemoglobin (OR = 0.973, 95%CI = 0.951-0.996) and hypertension (OR = 1.025, 95%CI = 1.007-1.044) increased the risk of complications in biopsied patients.

CONCLUSION

Renal biopsy is a safe procedure with a low risk of complications when strict biopsy protocol is observed. Correction of anaemia and blood pressure is to be considered before the biopsy.

Predicting Fibrosis Progression in Renal Transplant Recipients Using Laser-Based Infrared Spectroscopic Imaging

Renal transplants have not seen a significant improvement in their 10-year graft life. Chronic damage accumulation often leads to interstitial fibrosis and tubular atrophy (IF/TA) and thus graft function loss over time. For this reason, IF/TA has been the chief suspect for a potential prognostic marker for long term outcomes. In this study, we have used infrared spectroscopic (IR) imaging to interrogate the biochemistry of regions of fibrosis from renal transplant biopsies to identify a biochemical signature that can predict rapid progression of fibrosis. IR imaging represents an approach that permits label-free biochemical imaging of human tissues towards identifying novel biomarkers for disease diagnosis or prognosis. Two cohorts were identified as progressors (n = 5, > 50% fibrosis increase between time points) and non-progressors (n = 5, < 5% increase between time points). Each patient had an early time point and late time point biopsy. Collagen associated carbohydrate moieties (ν(C–O), 1035 cm⁻¹ and ν(C–O–C),1079 cm⁻¹) spectral ratios demonstrated good separation between the two cohorts (p = 0.001). This was true for late and early time point biopsies suggesting the regions of fibrosis are biochemically altered in cases undergoing progressive fibrosis. Thus, IR imaging can potentially predict rapid progression of fibrosis using histologically normal early time point biopsies.

Innovative Perspective: Gadolinium-Free Magnetic Resonance Imaging in Long-Term Follow-Up after Kidney Transplantation

Since the mid-1980s magnetic resonance imaging (MRI) has been investigated as a non- or minimally invasive tool to probe kidney allograft function. Despite this long-standing interest, MRI still plays a subordinate role in daily practice of transplantation nephrology. With the introduction of new functional MRI techniques, administration of exogenous gadolinium-based contrast agents has often become unnecessary and true non-invasive assessment of allograft function has become possible. This raises the question why application of MRI in the follow-up of kidney transplantation remains restricted, despite promising results. Current literature on kidney allograft MRI is mainly focused on assessment of (sub) acute kidney injury after transplantation. The aim of this review is to survey whether MRI can provide valuable diagnostic information beyond 1 year after kidney transplantation from a mechanistic point of view. The driving force behind chronic allograft nephropathy is believed to be chronic hypoxia. Based on this, techniques that visualize kidney perfusion and oxygenation, scarring, and parenchymal inflammation deserve special interest. We propose that functional MRI mechanistically provides tools for diagnostic work-up in long-term follow-up of kidney allografts.

Kidney allograft surveillance biopsy practices across US transplant centers: A UNOS survey

BACKGROUND

The approach to the diagnosis and management of subclinical rejection (SCR) in kidney transplant recipients remains controversial.

METHODS

We conducted a survey through UNOS across US transplant centers regarding their approach to surveillance biopsies and reasons for the nonperformance of surveillance biopsies.

RESULTS

Responses were obtained from 106/238 centers (45%), and only 18 (17%) of the centers performed surveillance biopsies on all patients and 22 (21%) performed biopsy for select cases. The most common time points for surveillance biopsies were 3 and 12  months post-transplant. The common reasons for not performing biopsies were low yield (n = 44, 65%) and the belief that it will not change outcome (n = 24, 36%). The incidence of SC-TCMR was ≥ 10% among 39% of centers. The mean serum creatinine was slightly worse by 0.06 mg/dL at 1 year and 0.07 mg/dL at 3 years among centers performing biopsy, P < .0001. The. 1-and 3-year Observed-Expected (O-E) graft survival was similar among centers performing biopsies vs. those not performing biopsy (P = .07, .88).

CONCLUSION

Only 17% of US centers perform surveillance biopsies, with another 21% performing surveillance biopsies in select cases (among centers that responded to the survey). Greater uniformity in the approach and management of this condition is of paramount importance.

To what extent estimated or measured GFR could predict subclinical graft fibrosis: a comparative prospective study with protocol biopsies

Monitoring of allograft function entails methods more accurate than serum creatinine and creatinine-based GFR equations (eGFR). This prospective trial aimed at investigating the diagnostic accuracy of creatinine- and cystatin C-based eGFR with measured GFR (mGFR) and compared them with graft fibrosis detected by protocol biopsies (PBx). Forty-four kidney transplant recipients were enrolled. PBx were obtained postengraftment and at 6th and 12th months. GFR was measured by Tc-99m DTPA at 3th, 6th, and 12th months after transplantation. Significant correlation existed between eGFR and mGFR at 3, 6, and 12 months (P < 0.0001). Cystatin C-based Hoek and Larsson equations had the lowest bias and highest accuracy. The sum of interstitial fibrosis and tubular atrophy score increased from implantation to 6th and 12th months (0.52 ± 0.79, 0.84 ± 0.88, 1.50 ± 1.35). This was accompanied by reduction of mGFR from 54.1 ± 15.2 to 49.9 ± 15.2 and 46.8 ± 16.5 ml/min/1.73 m(2) , while serum creatinine, cystatin C, and eGFR remained stable. Neither creatinine- nor cystatin C-based GFR equations are reliable for detecting insidious graft fibrosis. In the first year after transplantation, mGFR, with its best proximity to histopathology, can be used to monitor allograft function and insidious graft fibrosis.

The short-term impact of protocol biopsies in a live-related renal transplant program using tacrolimus based immunosuppression

The aim of the study was to assess the impact of protocol biopsies in a live-related renal transplant program using tacrolimus-based immunosuppression in the short term. Eighty-three live-related transplant recipients were randomly allocated to protocol biopsy group (Group I, n = 40) and a control group (Group II, n = 43). Other immunosuppressants in these groups consisted of either mycophenolate mofetil or azathioprine and steroids. Protocol biopsies were conducted in biopsy group at 1, 6, and 12 months post-transplant. The non-biopsy group was followed by serial serum creatinine and biopsies in them were conducted as and when clinically indicated. Both groups were analyzed at 12 months with respect to graft function and survival. The two groups were similar with respect to age, number of dialysis pre-operatively, tacrolimus levels, induction therapy, donor age, and donor glomerular filtration rate. Forty protocol biopsies were conducted at 1 month, 31 at 6 months, and 26 at 12 months. The prevalence of sub-clinical rejection at 1, 6, and 12 months in these biopsies was 17.5%, 11.2%, and 10.3%, respectively. The prevalence of calcineurin inhibitor toxicity during same period was 15%, 15.5%, and 14.4%, respectively. The cumulative rejection rate in Group I and Group II at 12-month follow-up was 10.3% and 11.3% (P = 0.78), respectively, and cumulative calcineurin inhibitor toxicity at 12 months was 14.4% and 9.3% (P = 0.59), respectively, were not statistically significant. There was no difference in graft survival and function at 1 year. Protocol biopsies have a limited role in a well-matched renal transplant program with tacrolimus-based immunosuppression in the short term. However, the long-term impact of protocol biopsies needs further evaluation.

Surveillance biopsies in children post-kidney transplant

Surveillance biopsies are increasingly used in the post-transplant monitoring of pediatric renal allograft recipients. The main justification for this procedure is to diagnose early and presumably modifiable acute and chronic renal allograft injury. Pediatric recipients are theoretically at increased risk for subclinical renal allograft injury due to their relatively large adult-sized kidneys and their higher degree of immunological responsiveness. The safety profile of this procedure has been well investigated. Patient morbidity is low, with macroscopic hematuria being the most common adverse event. No patient deaths have been attributed to this procedure. Longitudinal surveillance biopsy studies have revealed a substantial burden of subclinical immunological and non-immunological injury, including acute cellular rejection, interstitial fibrosis and tubular atrophy, microvascular lesions and transplant glomerulopathy. The main impediment to the implementation of surveillance biopsies as the standard of care is the lack of demonstrable benefit of early histological detection on long-term outcome. The considerable debate surrounding this issue highlights the need for multicenter, prospective, and randomized studies.

Treatment of subclinical injuries detected by protocol biopsy improves the long-term kidney allograft function: a single center prospective randomized clinical trial

BACKGROUND

The long-term benefit of early treatment of subclinical disorders detected in kidney allografts by protocol biopsy is controversial. We collected 145 protocol biopsies from 113 recipients for comparison with 51 control patients in a single-center, prospective, randomized trial.

METHODS

Ultrasound-guided biopsies were performed in recipients with stable renal function. Samples were taken at 3 (n=66) and/or 12 months (n=79) after transplantation. The biopsies were evaluated according to the Banff scheme, and patients were treated based on the diagnosis. Changes in glomerular filtration rate (GFR) were compared with 51 patients who were randomized as a control group.

RESULTS

The findings on 38 samples (29%) were considered to be normal. Based on the pathology findings, such as subclinical acute rejection (n=23), calcineurin inhibitor toxicity (n=28), chronic rejection (n=6), and other specific pathologies (n=23), including polyoma virus nephropathy (n=2), induced treatment among 82 recipients (57%). Significantly better graft function was observed at 3-year follow-up among the biopsy group, compared with controls: GFR = 46.0 ± 13.8 vs 35 ± 15 mL/min (P=.002). The 5-year graft survival was significantly higher in the biopsy (81%) than in the control (55.6%) group (P=.0012).

CONCLUSION

Early detection and treatment of subclinical pathologies improved graft function and long-term survival. Protocol biopsies were a valuable tool for posttransplantation management.

Contrast-enhanced sonography of postbiopsy arteriovenous fistulas in kidney grafts

PURPOSE

To assess the usefulness of contrast-enhanced ultrasonography (CE-US) in the visualization of a kidney graft following a biopsy that was complicated by an arteriovenous fistula (AVF).

METHODS

Four postrenal transplant patients who had developed AVFs following graft biopsy were examined using standard US and CE-US. Additionally, follow-up examinations were conducted using CE-US, at 4-6 weeks and 10-12 weeks following fistula closure.

RESULTS

The fistulas were detected using color Doppler US, Power Doppler US, and B-flow technique. Reduced parenchymal flow was only detected in one case using standard flow visualization techniques. CE-US allowed for the visualization of regions of disturbed parenchymal perfusion that were not visible in the standard examinations. At follow-up, B-mode ultrasound and standard flow examinations appeared normal. However, all contrast-enhanced images showed clearly demarcated residual regions of reduced parenchymal perfusion, in areas where the fistulas had been previously present.

CONCLUSIONS

A posttraumatic AVF reduces parenchymal perfusion in the affected region. CE-US examination may help in monitoring fistulas during the active phase and following spontaneous closure.

Revisiting the Natural History of IF/TA in Renal Transplantation

Despite the decrease in incidence of early clinical and subclinical rejection and increased 1-year graft survival in renal transplant patients, the rate of graft loss after the first year has been only moderately improved. Protocol biopsies obtained in the first year have shown rapid increase in the prevalence of IF/TA. This finding has been correlated with later allograft dysfunction and loss, mostly in cases of concomitant interstitial inflammation and fibrosis (1). The landmark study by Nankivell et al., performed in recipients of organs from deceased young donors under early cysclosporin-based immunosuppression, suggested two distinct phases of injury involved in IF/TA: an early tubulo-interstitial damage from ischemic injury and allograft rejection and, beyond 1 year, microvascular, glomerular and additional tubulo interstitial injury interpreted as secondary CsA toxicity (2). Since this publication, chronic antibody-mediated rejection has been better identified as leading causes of late graft dysfunction. Moreover, a recent study showed that most cases of kidney graft loss have an identifiable cause that is not idiopathic IF/TA or CNI toxicity and that alloimmunity remains the most common mechanism leading to failure (3). Thus, with the current immunosuppressive regimens and the input of molecular phenotyping, one may question the natural history of IF/TA.

The pathology of chronic allograft dysfunction

Chronic allograft dysfunction is associated with a variety of fibrosing/sclerosing changes in the allograft. Fibrosis is multifactorial, a final pathway following varying types of injury. Using a range of diagnostic criteria, the pathologist can and should define specific lesions enabling identification of pathogenic processes affecting the allograft. Although some cases remain 'interstitial fibrosis and tubular atrophy, no specific cause', specific diagnoses can be made in most cases. Drug toxicity, bacterial or viral infection, hypertension, obstruction, recurrent or de novo renal diseases, and acute and chronic cell- and/or antibody-mediated rejection can be diagnosed in this setting. Of particular concern is a combination of persistent inflammation and fibrosis, which has repeatedly been shown to be correlated with poor graft outcomes. Identification of ongoing activity, and the stage of evolution of fibrosis/sclerosis provides important diagnostic and therapeutic information for patient management. Histological, immunohistological, ultrastructural, and molecular studies may be needed to adequately assess the kidney in the setting of chronic allograft dysfunction. Protocol biopsies may provide diagnostic insights in early stages of late graft deterioration, or even before evident dysfunction develops.

Post-transplant monitoring of renal allografts: are we there yet?

Transplantation has emerged as the therapy of choice for many patients with end organ failure. One of the major goals is to tailor immunosuppressive therapy to the individual needs of every patient to balance the risk for rejection and over-immunosuppression. This will require diagnostic tools that can detect harmful processes in the allograft early, and that can be measured repeatedly. This review will consider recent advances in our understanding of the molecular nature of these processes and how this information is being utilized to design novel diagnostic assays to non-invasively monitor allografts. Highlighted is the need for large-scale prospective multi-centre studies to validate assays that show early promise in single centre studies.

The renal biopsy

CONTEXT

The first renal biopsy was carried out more than a century ago, but its widespread introduction into clinical use, beginning in the 1950s, helped develop nephrology into the powerful subspecialty of internal medicine that it is today. In the past 25 years, the use of the spring-loaded biopsy gun, in combination with newer visualization techniques, including ultrasound and computed axial tomography scanning, has led to greater tissue yield and to a much lower risk of complication. During this same time, our understanding of renal pathology has increased many fold. Correct fixation and processing of renal biopsy tissue is critical, and the laboratory must be skilled with renal biopsy light microscopy, immunohistochemistry, and transmission electron microscopy preparation.

OBJECTIVES

To provide an overview of the renal biopsy, including the techniques and its complications, and to summarize proper laboratory methods for processing renal biopsy tissue.

DATA SOURCES

This article is based on a review of the literature and on the experience of the author.

CONCLUSIONS

The experienced nephropathologist, knowledgeable in both renal medicine and pathology and thus able to correlate subtle tissue-derived information with appropriate clinical data, remains the most important key to the development of an accurate clinicopathologic diagnosis.

Noninvasive prediction of organ graft rejection and outcome using gene expression patterns

Development of predictive, diagnostic, and prognostic biomarkers of allograft status and outcome is important and challenging, and may be rewarded with individualized therapy for the organ graft recipient. Herein, we summarize noninvasive messenger RNA profiling studies for ascertaining allograft status and outcome. Nucleic acid-based biomarkers of allograft status have been developed by several laboratories, but the studies have primarily been single center investigations. Ongoing multicenter trials including the Clinical Trials in Organ Transplantation (https://www.ctotstudies.org) should help further to define the clinical utility of noninvasively developed messenger RNA profiles as biomarkers of allograft status and outcome.

Lack of benefit of early protocol biopsies in renal transplant patients receiving TAC and MMF: a randomized study

We conducted a randomized, multicenter study to determine whether treatment of subclinical rejection with increased corticosteroids resulted in beneficial outcomes in renal transplant patients receiving tacrolimus (TAC), mycophenolate mofetil (MMF) and prednisone. One hundred and twenty-one patients were randomized to biopsies at 0,1,2,3 and 6 months (Biopsy arm), and 119 to biopsies at 0 and 6 months only (Control arm). The primary endpoint of the study was the prevalence of the sum of the interstitial and tubular scores (ci + ct)> 2 (Banff) at 6 months. Secondary endpoints included clinical and subclinical rejection and renal function. At 6 months, 34.8% of the Biopsy and 20.5% of the Control arm patients had a ci + ct score >or= 2 (p = 0.07). Between months 0 and 6, clinical rejection episodes were 12 in 10 Biopsy arm patients and 8 in 8 Control arm patients (p = 0.44). Overall prevalence of subclinical rejection in the Biopsy arm was 4.6%. Creatinine clearance at 6 months was 72.9 +/- 21.7 in the Biopsy and 68.90 mL/min +/- 18.35 mL/min in the Control arm patients (p = 0.18). In conclusion, we found no benefit to the procurement of early protocol biopsies in renal transplant patients receiving TAC, MMF and prednisone, at least in the short term. This is likely due to their low prevalence of subclinical rejection.

Surveillance renal transplant biopsies and subclinical rejection at three months post-transplant in pediatric recipients

Subclinical acute rejection (SCR) has been increasingly recognized in adult renal transplant recipients with the advent of surveillance biopsies. However, in children, surveillance biopsies are not routinely performed at most centers. Therefore, the incidence, predisposing factors, treatment, and clinical outcomes of SCR remain unclear in children. From August 2004 to December 2005, we performed 36 protocol biopsies at three months post-transplantation. All patients had received induction therapy with basiliximab and were maintained on prednisone, MMF, and tacrolimus. Sixteen cases of SCR were detected by biopsy (44%). Age, gender, race, donor source, or serum creatinine did not discriminate between children with SCR and those with normal biopsies. All cases of SCR were treated with high doses of methylprednisolone. At one yr post-transplant, renal function was similar in children with SCR to those with normal surveillance biopsies (p = 0.62). Because of the high incidence of SCR, the maintenance dose of MMF was increased by 50% in 20 children transplanted after December 2005. This resulted in a significant decline in the incidence of SCR from 44 to 15% (p < 0.05). However, the incidence of polyomavirus (BK) viremia also increased significantly in these children (p < 0.005).

CONCLUSION

A high incidence of SCR was found on surveillance biopsies at three months post-transplant and could not be predicted by age, gender, race, donor source, or serum creatinine. The occurrence of SCR declined significantly by increasing the dose of MMF, but resulted in an increase in BK viremia. We conclude that surveillance biopsies provide valuable information in the management of pediatric renal transplant recipients. Increasing immunosuppression to avoid SCR should be weighed against the risk for infection.

Low incidence of adverse events in outpatient pediatric renal allograft biopsies

In 1999, our center implemented a policy of outpatient protocol biopsies as standard practice for the clinical management of pediatric renal allograft recipients. In order to determine the safety of this procedure, we conducted a retrospective chart audit of all outpatient renal allograft biopsies performed at our center. Biopsies were performed under conscious (midazolam) or procedural (propofol/fentanyl) sedation. Localization of the lower pole of the renal allograft was achieved with renal ultrasound. Using a Biopty gun with a 16-gauge needle, two cores were obtained. Patients were discharged four h post-biopsy. Patient demographics, hospital length of stay (LOS), specimen adequacy (per Banff criteria) and major and minor adverse events were recorded in a central database. Data were expressed as mean +/- SD. From June 1999 to July 2004, we performed 162 biopsies in 43 pediatric renal allograft recipients. Most patients underwent extraperitoneal transplantation (42/43, 97.7%) and were greater than five yr of age at biopsy (129/131 biopsies, 98.5%). The majority of these procedures (131/162, 80.9%) were conducted in the outpatient department, with 113 of 131 (86.3%) being obtained for protocol (n = 89) and one-month follow-up acute rejection therapy (n = 24) indications. Patients underwent 3.7 +/- 2.7 biopsies (range = 1-11). Specimen adequacy was achieved in 119 of 124 (96.0%) of documented cases. The overall incidence of adverse events was 12 of 131 (9.2%) biopsies, all of which were minor in severity. Macroscopic hematuria was the most common minor adverse event, occurring after 11 of 131 (8.4%) biopsies. While macroscopic hematuria prolonged LOS (adverse events vs. no adverse events: 23.0 +/- 26.0 vs. 8.6 +/- 4.1 h, p = 0), none of these episodes required major surgical or radiographic interventions. We conclude that in patients greater than five yr of age with extraperitoneal renal allografts, outpatient protocol biopsies using a 16-gauge needle are sufficiently safe to justify their inclusion in the routine clinical management of pediatric renal allograft recipients and in pediatric clinical trials.