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The Real-life Experience of Developing and Commercializing TruGraf, a Validated Non-invasive Transplant Biomarker

Authors:
Sci Forschen
Open HUB for Sc i e n t if i c R e s e a r c h
Journal of Biochemistry and Analycal studies
ISSN 2576-5833
| Open Access
J Biochem Analyt Stud | JBAS
1
REVIEW ARTICLE
The Real-life Experience of Developing and Commercializing TruGraf, a Validated
Non-invasive Transplant Biomarker
M Roy First1,2*, Steven B Kleiboeker3, Stanley Rose1, John J Friedewald2, and Michael M Abecassis4
1Transplant Genomics Inc, USA
2Northwestern University, Comprehensive Transplant Center, USA
3Viracor Eurons Clinical Diagnoscs, USA
4University of Arizona College of Medicine-Tucson, USA
Received: 24 Apr, 2020 | Accepted: 11 May, 2020 | Published: 18 May, 2020
Volume 4 - Issue 2
severe rejection, such as fever, pain over the gra, or decreased
urine output may be present, but are infrequent ndings with
current immunosuppressive regimens. us, current non-invasive
monitoring only detects rejection when it is advanced and only
aer signicant, and potentially irreversible damage to the gra has
occurred. Indication or for cause biopsies are typically performed to
determine the cause of acute renal dysfunction.
Biopsies are expensive, invasive, and suer from signicant
variability in interpretation [12]. Moreover, biopsies put patients at
risk for signicant complications such as infection, bleeding, and
even gra loss, in addition to being painful and inconvenient [13].
However, indication biopsies remain essential in the management
of patients with renal dysfunction and are used ubiquitously
by transplant programs. In sharp contrast, while a number of
transplant programs have adopted the routine use of surveillance
biopsies to detect subclinical acute rejection (subAR) in patients
with stable renal function, several factors have discouraged other
programs from following suit. These include but are not limited to
all the issues stated above, but, in addition, stable patients undergo
indiscriminate biopsies resulting in negative (unnecessary)
invasive procedures the vast majority of the time. Thus, a non-
invasive monitoring strategy that replaces invasive protocol biopsies
is sorely needed and has been the focus of several investigators in the
past few years.
*Corresponding author: M Roy First, Transplant Genomics Inc, Northwestern University, Comprehensive Transplant Center, USA, Tel:
7736778682; E-mail: roy@transplantgenomics.com
Citaon: First MR, Kleiboeker SB, Rose S, Friedewald JJ, Abecassis MM (2020) The Real-life Experience of Developing and Commercializing TruGraf,
a Validated Non-invasive Transplant Biomarker. J Biochem Analyt Stud 4(2): dx.doi.org/10.16966/2576-5833.123
Copyright: © 2020 First MR, et al. This is an open-access arcle distributed under the terms of the Creave Commons Aribuon License, which
permits unrestricted use, distribuon, and reproducon in any medium, provided the original author and source are credited.
Abstract
Despite improvement in short-term outcomes, long-term results for kidney transplant recipients remain subopmal. Immunological rejecon is
a leading cause of gra failure and recent research points to undetected “silent” subclinical acute rejecon as a key component of this problem.
While biopsies remain the gold-standard method for detecng silent rejecon, non-invasive methods oer signicant advantages especially in terms
of paent safety and for serial monitoring of stable paents. This manuscript details the real-life challenges involved in the ulmately successful
development and commercializaon of TruGraf, a clinically validated, blood-based gene expression assay that oers the potenal to reduce the use
of surveillance (protocol) biopsies in renal transplant recipients with stable renal funcon.
Keywords: Non-invasive transplant biomarker; TruGraf; Kidney transplantaon; Biopsies; Renal funcon
Introduction
Kidney transplantation is the optimal treatment for most patients
with chronic renal failure [1]. However, the long term success of kidney
transplantation is far from optimal [2]. In 2017, 10-year all-cause gra
failure was 49.7% for deceased donor kidney recipients and 34.1%
for living donor kidney transplants [3]. Immunological rejection,
a major cause of gra failure, is driven by attack of the gra by T
cells (T cell mediated rejection, or TCMR) or antibodies (antibody
mediated rejection, or ABMR), or in some cases a combination of
these two mechanisms (mixed rejection). A key early contributor to
long-term gra loss is subclinical immune injury that leads to chronic
damage of the renal allogra [4-8]. Until recently there have been no
commercially available fully validated non-invasive tests to monitor
patients with stable renal function for silent rejection [9]. As a result, a
signicant number of centers rely on surveillance (protocol) biopsies
to detect early silent rejection, whereas other centers who choose not
to perform these wait for clinical evidence of gra injury and damage
[10,11].
Situational Analysis
Standard non-invasive monitoring to detect kidney injury
secondary to rejection or other causes includes measuring serum
creatinine levels and immunosuppressive drug levels, both of
which are insensitive and nonspecic. Clinical manifestations of
Sci Forschen
Open HUB for Sc ie n t i f i c R e s e a r c h
Citaon: First MR, Kleiboeker SB, Rose S, Friedewald JJ, Abecassis MM (2020) The Real-life Experience of Developing and Commercializing
TruGraf, a Validated Non-invasive Transplant Biomarker. J Biochem Analyt Stud 4(2): dx.doi.org/10.16966/2576-5833.123 2
Journal of Biochemistry and Analycal studies
Open Access Journal
Previous investigators focused on developing non-invasive
biomarkers in the urine and blood to diagnose rejection in patients
with gra dysfunction (clinical acute rejection-cAR) in an attempt
to replace indication biopsies. ere are two major fallacies to this
approach: rst, while some patients with subAR develop cAR, others
exhibit ongoing subAR causing more chronic gra injury; second,
in the absence of paired biopsies for each sample, it is dicult to be
certain that bio-informatics approaches which yield positive results
from these samples are real. For this reason, we set out to develop a
biomarker specic for subAR by using only blood samples paired with
protocol biopsies in patients with stable renal function.
Development of a validated peripheral blood biomarker for
subAR
Identifying the need for a non-invasive replacement for biopsies in
stable patients, we set out to discover and validate a peripheral blood
biomarker to detect subAR in these patients as a “rule in” test, similar
to biopsies. While our clinical trials and sample collection regimens
were well designed, the evidentiary data and biomarker performance
that resulted caused us to rethink the context of use (COU) of the
biomarker.
Subclinical acute rejection (subAR), also referred to as “silent”
rejection, is histologically dened acute rejection characterized by
tubulointerstitial mononuclear cell inltration identied from a biopsy
specimen in a patient with normal or stable renal function [4-8]. In the
NIH-sponsored CTOT-08 study of 307 kidney transplant recipients
[7], the natural prevalence of subAR, based on surveillance biopsies,
was 20% at 3-6 months, and 25% at 12 and 24 months surveillance
biopsies, with an overall prevalence of 35% [7]. Of note, 80% of
the subAR was of the borderline variety when classied by central
pathology using the Ban criteria [14], and importantly, the biopsy
was normal in 75% of cases. At the two year time point, patients with
subAR on surveillance biopsies had worse outcomes than patients
who did not. is was based on a composite clinical endpoint (CCE)
consisting of biopsy-proven acute rejection (BPAR) on any “for-
cause biopsy” by central read, or a 24-month biopsy (central read)
showing evidence of chronic injury measured by interstitial brosis
and tubular atrophy (IFTA) of Ban grade ≥ II IFTA (ci ≥ 2 or ct ≥ 2),
or a decrease in estimated glomerular ltration rate (GFR) by >10mL/
min/1.73m2 between 4 and 24 months post-transplant [7]. SubAR was
also associated with a higher frequency of both class I and class II de
novo donor specic antibody (dnDSA) development [7,15].
In addition to the CTOT-08 data shown above, a number of clinical
studies have also recently associated subAR with poor outcomes [4-
8,15-19]. A study in recipients with a rapid steroid withdrawal protocol
compared outcomes in patients with no inammation and those with
subclinical inammation on a 3-month surveillance biopsy. In the
patients with subclinical inammation, the serum creatinine levels were
signicantly higher at 24 months, and the allogra chronicity index
on biopsy, the rate of subsequent BPAR and development of dnDSA
were all signicantly increased at 12 months [16]. A large Australian
study compared outcomes in patients with normal biopsies, those with
borderline rejection, and those with T cell mediated acute rejection.
Compared to patients with normal biopsies, patients with borderline
rejection had worse renal function, more IFTA, subsequent acute
rejection, allogra failure and patient mortality [7]. A recent study
in 103 pediatric renal transplant recipients that examined subclinical
inammation phenotypes and long-term outcomes aer pediatric
kidney transplantation, highlights the importance and treatment of
subAR [18]. In this study, surveillance biopsies were performed in
rst 6 months and a composite endpoint (CEP) of acute rejection and
gra failure was measured at 5 years. e CEP was reached by 41%
for treated borderline rejection vs. 67% for untreated (p<0.001) [18].
Additionally, another recent publication has shown that borderline
early acute rejection is associated with the development of late acute
rejection and gra loss [19].
e Trials and Tribulations of a) developing and b)
commercializing a non-invasive biomarker for subAR
Development: e TruGraf® Blood Gene Expression Test
(Transplant Genomics, Inc, Manseld, MA) is a microarray-based
assay that analyzes gene expression proles (GEP) in the peripheral
blood. Our initial strategy was to develop a “rule in” test, whereby a
positive test would be highly predictive of a positive biopsy (subAR).
We used a locked support vector machine (SVM) based classier
with a bootstrap to prevent over-tting of the discovery set for
internal validation as the bio-informatics approach [20]. We found
two interesting observations: rst, at dierent thresholds, we traded
PPV for NPV to the point that a “rule in” test was not possible using
this approach. We then switched to Random Forest (RF) as the bio-
informatics approach [21] and used a dierent threshold, but again
it was evident that the intended use of the biomarker would need to
change. Because the performance metrics were better with RF, we
proceeded to use RF but picked thresholds more favourable for a “rule
out” test [21]. e product was a GEP classier that associates with
either a normal protocol kidney biopsy (Transplant eXcellence-TX)
or the absence of a normal biopsy (not-TX) in patients with stable
renal function. All aspects of discovery and external validation of the
TruGraf test were performed on blood samples paired with biopsies
from prevalent cohorts. For the purpose of validation, the model
derived from pre-selected bio-informatics and the threshold used to
test performance on the discovery cohort were locked. ese data
led us to use this approach for external validation in an early access
program (EAP) for patients [22]. e external clinical validation from
seven EAP transplant centers dened the key clinical performance
parameters for this assay, as summarized in table 1 and gure 1. In
this study, the high negative predictive value (NPV) of TruGraf was
demonstrated in clinical use, making it a strong rule-out test. Over
90% of stable patients who received a TX results were conrmed to
have an immune quiescent phenotype, meaning that a physician can
have a high degree of condence that a patient who tests as TX does
not harbour silent subclinical rejection. Importantly this study also
found that up to 65% of surveillance biopsies could be avoided in the
cohort tested. Unpublished data involving analysis of an additional
129 biopsy-conrmed blood samples provided by Northwestern
University (originally used for the CTOT-08 study) revealed identical
performance metrics for TruGraf (NPV of 90%). A fourth publication
described the impact of TruGraf results on physician decision
making for clinical decisions [23]. is study highlighted the high
degree of condence physicians place in the ability of TruGraf to
provide valuable, added information that could lead to avoidance of
unnecessary surveillance biopsies as summarized in table 2. In the
prospective study (n=45) 87.0% of physician responses indicated that
the result of the TruGraf test supported their management decision in
a patient with stable renal function, with a corresponding rate in the
retrospective study (n=192) of 87.5% [23].
As a result of these experiences, we changed the proposed COU
from replacing surveillance biopsies for detecting subAR, to reducing
the number of necessary biopsies in stable patients which should lead
to many less invasive procedures (Table 1) as well as signicantly less
negative or unnecessary biopsies. e COU proposed in the recent
approval from CMS states that “e TruGraf test is intended for use in
Sci Forschen
Open HUB for Sc ie n t i f i c R e s e a r c h
Citaon: First MR, Kleiboeker SB, Rose S, Friedewald JJ, Abecassis MM (2020) The Real-life Experience of Developing and Commercializing
TruGraf, a Validated Non-invasive Transplant Biomarker. J Biochem Analyt Stud 4(2): dx.doi.org/10.16966/2576-5833.123 3
Journal of Biochemistry and Analycal studies
Open Access Journal
kidney transplant recipients with stable renal function as an alternative
to surveillance biopsies in facilities that utilize surveillance biopsies”.
While primarily used to rule out subAR, it is expected that both centers
that perform or do not perform surveillance biopsies can use the test
to assess the need for a surveillance biopsy in stable patients [24].
Figure 2 illustrates a proposed approach for implementation of
TruGraf into clinical care for kidney transplant recipients. For
patients with stable renal function, a TruGraf result of “TX”
identifies those who have a high likelihood of immune quiescence
and a low likelihood of histologically defined rejection at the
borderline level or higher. A result of “Not-TX” identifies those
in whom silent rejection cannot be confidently ruled out, and
thus carry a higher risk of immune activation and borderline or
higher rejection. Patients with a “Not-TX” result might benefit
from further evaluation and possibly a change in therapy. Early
identification of these patients potentially allows better allocation
of physician resources, and potential reversal of the process before
permanent damage to the donated kidney occurs.
Pathway to commercialization of TruGraf: Developed in 2011, the
Molecular Diagnostic Services (MolDX) program is run by Palmetto
GBA, a centers for Medicare and Medicaid Services (CMS) Medicare
administrative contractor. It performs the following functions:
• Facilitates detailed and unique identication through registration
of molecular diagnostics tests to facilitate claims processing and
to track utilization.
• Establishes clinical utility expectations. Completes technical
assessments of published test data to determine clinical utility
and coverage.
CMS approved reimbursement for commercial TruGraf testing on
November 25, 2019.
A recently published study evaluated the clinical validity of serial
TruGraf testing in stable kidney transplant recipients in a center
not utilizing surveillance biopsies [25]. Serum creatinine levels and
TruGraf testing at multiple time points were correlated with clinical
follow-up in 28 patients. e concordance of TruGraf results, when
compared with independent clinical assessment of testing, was 77%
Adjusted to 24.5% subAR
prevalence % TX (biopsy
spared)
NSensivity Specicity PPV NPV PPV NPV
All samples 192 76.5% 73.4% 38% 93.5% 48% 91% 65%
Paired blood and biopsy
subset 99 70.8% 74.7% 47% 89% 48% 89% 64%
Table 1: Summary of TruGraf v1 performance characteriscs in a mulcenter, observaonal study [22].
NPV=negave predicve value;
PPV=posive predicve value.
Timing of Quesonnaire Clinical Ulity Feedback Yes No
Prospecve (n=45)
Did the TruGraf result support your decision on how to manage a paent with stable serum
creanine? 39(87%) 6(13%)
Does the TruGraf result encourage you to use TruGraf serial tesng in future paent
management? 42(93%) 3(7%)
Retrospecve (n=192)
Would this result have had any impact on your management of your paent in terms of
maintaining or changing immunosuppression, changing frequency of clinic visits, or deciding
on Whether to do a biopsy or not?
168(87.5%) 24(12.5%)
Table 2: Responses from principal invesgators to prospecve and retrospecve quesonnaires [22].
Figure 1: Individual site accuracy of TruGraf results (n=192) showing
concordance between a TruGraf TX result and paent clinical
phenotype at each of the seven study sites [22].
Figure 2: Suggested use of TruGraf for kidney transplant recipients
in the rst 5 years post-transplant. Frequency of tesng and clinical
use of results is based on expert opinion. TX=Transplant excellence,
indicang immunological quiescence in the transplanted kidney; Not-
Tx=abnormal result.
Sci Forschen
Open HUB for Sc ie n t i f i c R e s e a r c h
Citaon: First MR, Kleiboeker SB, Rose S, Friedewald JJ, Abecassis MM (2020) The Real-life Experience of Developing and Commercializing
TruGraf, a Validated Non-invasive Transplant Biomarker. J Biochem Analyt Stud 4(2): dx.doi.org/10.16966/2576-5833.123 4
Journal of Biochemistry and Analycal studies
Open Access Journal
(54/70) for all tests; 79% (22/28) for test 1, 75% (21/28) for test 2,
and 79% (11/14) for test 3. e NPV in this study was 98.0%, and
analysis of clinical utility indicated that 77% of TruGraf results would
have aided in patient management. ese results indicate the value of
serial TruGraf testing in those transplant centers that do not perform
surveillance biopsies as part of their standard of care. e high NPV
conrms immune quiescence with a high degree of probability in
patients with a TruGraf test result of TX without the need to perform
a biopsy.
Conclusions
Silent subclinical rejection is frequent and a signicant contributor
to worse long term outcomes for kidney transplant recipients. Until
now subAR could only be ruled in or out by invasive and risky per
protocol surveillance biopsies, resulting in a signicant number
of unnecessary biopsies and therefore unnecessary risk to patients
compromising safety. us, non-invasive tests are clearly needed to
identify patients with stable renal function who are harbouring subAR
in their gras. In response to this statement of need, we rst set out to
develop a “rule in” test to replace the routine use of protocol biopsies
as the context of use. However, based on the evidentiary performance
data of our biomarker, we determined that it is best used as a “rule
out” test and then revised the proposed COU as the reduction of a
large proportion of protocol biopsies in programs that currently utilize
these; in those that do not, subjecting far fewer patients to the risks
of biopsies together with a reduction in the number of unnecessary
(negative) biopsies may provide an attractive monitoring strategy [24].
To these ends, TruGraf is the rst and only non-invasive test designed
and validated for use in ruling out silent subclinical rejection in kidney
transplant recipients with stable renal function.
Non-invasive blood testing can be done more frequently than
surveillance kidney biopsies, is signicantly less invasive, less painful
and risky for patients, and may result in a considerable cost savings to
the health delivery system.
Conict of Interest
MRF, SBK and SR are full-time employees of Eurons-Transplant
Genomics, who developed the TruGraf test described in this
manuscript. JJF and MMA are consultants to Eurons-Transplant
Genomics.
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TruGraf, a Validated Non-invasive Transplant Biomarker. J Biochem Analyt Stud 4(2): dx.doi.org/10.16966/2576-5833.123 5
Journal of Biochemistry and Analycal studies
Open Access Journal
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Commonly available clinical parameters fail to predict early acute cellular rejection (EAR, occurring within 6 months after transplant), a major risk factor for graft loss after kidney transplantation. We performed whole-blood RNA sequencing at the time of transplant in 235 kidney transplant recipients enrolled in a prospective cohort study (Genomics of Chronic Allograft Rejection [GoCAR]) and evaluated the relationship of pretransplant transcriptomic profiles with EAR. EAR was associated with downregulation of NK and CD8+ T cell gene signatures in pretransplant blood. We identified a 23-gene set that predicted EAR in the discovery (n = 81, and AUC = 0.80) and validation (n = 74, and AUC = 0.74) sets. Exclusion of recipients with 5 or 6 HLA donor mismatches increased the AUC to 0.89. The risk score derived from the gene set was also significantly associated with acute cellular rejection after 6 months, antibody-mediated rejection and/or de novo donor-specific antibodies, and graft loss in a cohort of 154 patients, combining the validation set and additional GoCAR patients with surveillance biopsies between 6 and 24 months (n = 80) posttransplant. This 23-gene set is a potentially important new tool for determination of the recipient's immunological risk before kidney transplantation, and facilitation of an individualized approach to immunosuppressive therapy.
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The pathological diagnosis of borderline rejection (BL‐R) denotes possible T cell mediated rejection (TCMR), but its clinical significance is uncertain. This single‐centre, cross‐sectional cohort study compared the functional and histological outcomes of consecutive BL‐R diagnoses (n=146) against normal controls (n=826) and acute TCMR (n=55) from 551 renal transplant recipients. BL‐R was associated with: contemporaneous renal dysfunction, acute tubular necrosis and chronic tubular atrophy (P<0.001); progressive tubular injury with fibrosis by longitudinal sequential histology (45.3% at 1 year); increased subsequent acute rejection (39.4%), allograft failure (P<0.001), and patient mortality (P=0.007). BL‐R detected by biopsy indicated for impaired function was followed by suboptimal functional recovery (46.3%), persistent inflammation (27.2%), and acute rejection episodes (50.0%) despite anti‐rejection treatment in 83.3%. By one year after BL‐R, the incidence of new‐onset microvascular inflammation (9.3%), C4d staining (22.3%), transplant glomerulopathy (13.3%), and de novo donor specific antibodies (31.5%) exceeded normal controls (P<0.05‐0.001). BL‐R inflammation in protocol biopsy persisted in 28.0% and progressed to acute rejection in 32.6%, however resolved in 61.6% of the untreated cases. In summary, BL‐R is a heterogeneous diagnostic grouping, ranging from mild inconsequential inflammation to clinically‐significant TCMR, which is capable of immune‐mediated tubular injury resulting in inferior functional, immunological and histological consequences. This article is protected by copyright. All rights reserved.
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The implementation of surveillance biopsies in pediatric kidney transplantation remains controversial. Surveillance biopsies detect subclinical injury prior to clinical dysfunction, which could allow for early interventions that prolong allograft survival. We conducted a single‐center retrospective cohort study of 120 consecutive pediatric kidney recipients, of whom 103 had surveillance biopsies ≤ 6 months post‐transplant. We tested the hypothesis that subclinical inflammation (borderline or T cell‐mediated rejection without clinical dysfunction) is associated with a 5‐year composite endpoint of acute rejection and allograft failure. Overall, 36% of subjects had subclinical inflammation, which was associated with increased hazard for the composite endpoint [adjusted hazard ratio 2.89 (1.27, 6.57); P<0.01]. Subjects with treated versus untreated subclinical borderline rejection had a lower incidence of the composite endpoint (41% versus 67%; P<0.001). Subclinical vascular injury (subclinical inflammation with Banff arteritis score > 0) had a 78% incidence of the composite endpoint versus 11% in subjects with no major surveillance abnormalities (P<0.001). In summary, we showed that subclinical inflammation phenotypes were prevalent in pediatric kidney recipients without clinical dysfunction and were associated with increased acute rejection and allograft failure. Once prospectively validated, our data would support implementation of surveillance biopsies as standard of care in pediatric kidney transplantation. This article is protected by copyright. All rights reserved.
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The kidney sessions of the 2017 Banff Conference focused on two areas: clinical implications of inflammation in areas of interstitial fibrosis and tubular atrophy (i-IFTA) and its relationship to T cell-mediated rejection (TCMR), and the continued evolution of molecular diagnostics, particularly in the diagnosis of antibody-mediated rejection (ABMR). In confirmation of previous studies, it was independently demonstrated by two groups that i-IFTA is associated with reduced graft survival. Furthermore, these groups presented that i-IFTA, particularly when involving >25% of sclerotic cortex in association with tubulitis, is often a sequela of acute TCMR in association with under-immunosuppression. The classification was thus revised to include moderate i-IFTA plus moderate or severe tubulitis as diagnostic of chronic active TCMR. Other studies demonstrated that certain molecular classifiers improve diagnosis of ABMR beyond what is possible with histology, C4d, and detection of donor-specific antibodies (DSA), and that both C4d and validated molecular assays can serve as potential alternatives and/or complements to DSA in the diagnosis of ABMR. The Banff ABMR criteria are thus updated to include these alternatives. Finally, the present report paves the way for the Banff scheme to be part of an integrative approach for defining surrogate endpoints in next generation clinical trials. This article is protected by copyright. All rights reserved.
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An e-mail-based market research survey focused on high-volume US adult transplant centers was developed and implemented to assess surveillance based on United Network for Organ Sharing/Scientific Registry of Transplant Recipients data: 51 to 100 transplants, 101 to 200 transplants, and more than 200 transplants. Eighty-three centers responded to the survey. Respondent centers represented 13,837/21,167 (65%) of the total kidney transplants in 2018. In total, 38/83 (46%) centers reported the use of surveillance biopsies—20 centers in all patients and 18 in select patients. Surveillance biopsies were performed in 37% (7/19) of centers performing 51 to 100 transplants annually, in 44% (15/34) doing 101 to 200 transplants, and in 53% (16/30) of centers doing more than 200 transplants. Of the 20 centers doing surveillance biopsies in all patients, 17/20 (85%) perform more than 100 annual transplants, and 3/20 (15%) perform less than 100 annual transplants. Of the 45 centers not currently doing surveillance biopsies, 13 (29%) used surveillance biopsies in the past; discontinuation was primarily due to patient inconvenience, adverse events, and cost. Using survey percentages, it is estimated that surveillance biopsies are performed in approximately 34% of kidney transplant recipients and that 74% of all surveillance biopsies occur in centers performing more than 100 kidney transplants per year.
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Background: We investigated the effect of clinical and subclinical T cell-mediated rejection (C-TCMR and SC-TCMR) on allograft histology, function, and progression. Methods: Adult kidney recipients with 2 protocol biopsies were divided into No-TCMR on biopsies (n = 104), SC-TCMR (n = 56), and C-TCMR (n = 32) in at least 1 biopsy. Chronicity (ci + ct + cg + cv) scores, renal function, and the burden of renal disease measured by area under the curve (serum creatinine, mg mo/dL) were compared. Results: Baseline characteristics were similar except for mean donor age and Kidney Donor Profile index scores. Patients with C-TCMR had higher mean serum creatinine, lower mean estimated glomerular filtration rate, and higher area under the curve with 95% confidence interval (75.2 [67.7-82.7]) as opposed to patients with SC-TCMR and No-TCMR (58.3 [53.6-62.9], 65.1 [58.8-71.5]), P = 0.0004. Chronicity scores were higher at 3 months in C-TCMR (2.30 ± 1.58) compared with SC-TCMR (2.02 ± 1.42) and No-TCMR (1.31 ± 1.18), P = 0.0001 and also at 12 months. At last follow-up, 18.8% patients with C-TCMR had ≥50% decline in estimated glomerular filtration rate from 3 months compared with 7% and 1% among No-TCMR and SC-TCMR groups (P = 0.038). Multivariate analyses revealed higher odds of Δ-creatinine ≥ 0.5 mg/dL from 3 months to last follow-up for C-TCMR (3.39 [95% confidence interval, 1.25-9.20]) versus No-TCMR (P = 0.016). Conclusions: Kidney transplant recipients with C-/SC-TCMR have heightened early allograft chronicity and worse renal function compared with those with No-TCMR. Progressive renal dysfunction was noted among patients with C-TCMR as opposed to SC-TCMR and No-TCMR.
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Non‐invasive biomarkers are needed to monitor stable patients following kidney transplantation (KT), as sub‐clinical acute rejection (subAR), currently detectable only with surveillance biopsies can lead to chronic rejection and graft loss. We conducted a multi‐center study to develop a blood‐based molecular biomarker for subAR using peripheral blood paired with surveillance biopsies and strict clinical phenotyping algorithms for discovery and validation. At a predefined threshold, 72‐75% of KT recipients achieved a negative biomarker test correlating with the absence of subAR (NPV: 78‐88%), while a positive test was obtained in 25‐28% correlating with the presence of subAR (PPV: 47‐61%). The clinical phenotype and biomarker independently and statistically correlated with a composite clinical endpoint (renal function, biopsy‐proven acute rejection, >grade 2 interstitial fibrosis and tubular atrophy), as well as with de novo donor‐specific antibodies. We also found that <50% showed histological improvement of subAR on follow up biopsies despite treatment, and that the biomarker could predict this outcome. Our data suggest that a blood‐based biomarker that reduces the need for the indiscriminate use of invasive surveillance biopsies, and that correlates with transplant outcomes could be used to monitor KT recipients with stable renal function, including after treatment for subAR, potentially improving KT outcomes. This article is protected by copyright. All rights reserved.
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The impact of Sub-Clinical Inflammation (SCI) noted on early kidney allograft biopsies remains unclear. This study evaluated the outcome of SCI noted on 3-month biopsy. A total of 273/363 (75%) kidney transplant recipients with a functioning kidney underwent allograft biopsies 3-months post-transplant. Among those with stable allograft function at 3 months, 200 biopsies that did not meet the Banff criteria for rejection were identified. These were Group I: No Inflammation (NI, n=71) and Group II: Subclinical Inflammation (SCI, n=129). We evaluated differences in kidney function at 24-months and allograft histology score at 12-month biopsy. SCI patients had a higher serum creatinine (1.6+0.7 vs 1.38+0.45;p=0.02) at 24-months post-transplant, and at last follow up at a mean of 42.5 months (1.69±0.9 vs 1.46±0.5 mg/dl; p=0.027). The allograft chronicity score (ci+ct+cg+cv) at 12-months post-transplant was higher in the SCI group (2.4 +1.35 vs.1.9+1.2;p=0.02). The incidence of subsequent rejections within the first year in SCI and NI groups was 24% vs 10%, respectively (p=0.015). De novo DSA within 12 months was more prevalent in the SCI group (12/129 vs 1/71, p=0.03). SCI is likely not a benign finding and may have long-term implications for kidney allograft function. This article is protected by copyright. All rights reserved.
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Background: The approach to the diagnosis and management of Sub-Clinical 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 non-performance 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<0.0001. The 1 and 3-year Observed - Expected [O-E] graft survival was similar among centers performing biopsies vs. those not performing biopsy (p=0.07, 0.88) 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 This article is protected by copyright. All rights reserved.
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Renal transplant biopsies to diagnose transplant pathology are routinely performed using ultrasound guidance. Few large studies have assessed the rate and risk factors of major biopsy complications. This study is a single-center 5-year retrospective cohort analysis of 2514 biopsies. Major complications occurred in 47 of 2514 patients (1.9%) and included hospitalization, transfusion of blood products, operative exploration and interventional radiology procedures. The complication rate among "cause" biopsies was significantly higher than in "protocol" biopsies (2.7% vs. 0.33%, p < 0.001). Complications presented on postbiopsy days 0-14, with the majority diagnosed on the same day as the biopsy and manifested by hematocrit drop, although the presence of such delayed presentation of complications occurring >24 h after the biopsy on days 2-14 is previously unreported. Specific patient characteristics associated with increased risk of a complication were increased age and blood urea nitrogen, decreased platelet count, history of prior renal transplant, deceased donor transplant type and use of anticoagulant medications but not aspirin. © 2015 The American Society of Transplantation and the American Society of Transplant Surgeons.