MolDX: Molecular Testing for Solid Organ Allograft Rejection

Title XVIII of the Social Security Act (SSA), §1862(a)(1)(A), states that no Medicare payment shall be made for items or services that “are not reasonable and necessary for the diagnosis or treatment of illness or injury or to improve the functioning of a malformed body member.”

42 CFR §410.32(a) Diagnostic x-ray tests, diagnostic laboratory tests, and other diagnostic tests: Conditions

CMS Internet-Only Manual, Pub. 100-02, Medicare Benefit Policy Manual, Chapter 15, §80 Requirements for Diagnostic X-Ray, Diagnostic Laboratory, and Other Diagnostic Tests, §80.1.1 Certification Changes

DEFINITIONS

For purposes of this policy the following definitions are used:

• AR – Acute Rejection
• ACR – Acute Cellular Rejection (also referred to as TCMR: T-cell mediated rejection)
• AMR – Antibody-Mediated Rejection
• AV – Analytical Validity
• CV – Clinical Validity
• cfDNA – Donor-Derived Cell-Free DNA
• GEP – Gene Expression Profiling
• SubAR - Subclinical acute rejection
• For-Cause – patient has clinical signs or symptoms of organ injury/rejection.
• Surveillance (Protocol) – patient is asymptomatic; no clinical signs or symptoms of organ injury/rejection.

This Medicare contractor will provide limited coverage for molecular diagnostic tests used in the evaluation and management of patients who have undergone solid organ transplantation. These tests can inform decision making along with standard clinical assessments in their evaluation of organ injury for active rejection (AR). These tests may be ordered by qualified physicians or providers operating within their scope of practice considering the diagnosis of AR, helping to rule in or out this condition and when assessing the need for or results of a diagnostic biopsy. They should be considered along with other clinical evaluations and results and may be particularly useful in patients with significant contraindications to invasive procedures.

Molecular diagnostic tests that assess a transplanted allograft for rejection status are covered when ALL of the following criteria are met:

• The test must provide information about at least one of the two following clinical status determinations:
• AR status
• Cellular or Antibody-mediated rejection (ACR or AMR) status
• The intended use of the test must be to inform clinical decision making as per the following:
• To assist in the evaluation of adequacy of immunosuppression or response to treatment, wherein a non-invasive or minimally invasive test can be used in lieu of a tissue biopsy, OR
• As a rule-out test for AR in validated populations of patients with clinical suspicion of rejection with a non-invasive or minimally invasive test to make a clinical decision regarding obtaining a biopsy, OR
• For further evaluation of allograft status for the probability of allograft rejection after a physician-assessed pretest review of clinical and biological factors concerning for risk of rejection, OR
• To assess rejection status in patients that have received a biopsy, but the biopsy results are inconclusive, unexpected given the patient’s clinico-laboratory presentation, or limited by insufficient material, OR
• To assess for subclinical rejection of an allograft (i.e., surveillance testing), according to a clinically validated cadence (in peer-reviewed published evidence or established national consensus guidelines) utilizing the minimum number of test timepoints that have demonstrated clinical utility appropriate for the specific transplant type.

• At this time, the current evidence supports a maximum number of surveillance timepoints for evaluation in the first-year post-transplantation as follows: Kidney (4), Heart (12), and Lung (12).
• After the first year, surveillance timepoints may continue at a decreased frequency of 2 per year.

• The test demonstrates analytical validity (AV), including an analytical and clinical validation for any given measured analytes, and has demonstrated equivalence or superiority for sensitivity or specificity (depending on intended use) of detecting allograft rejection to other already-accepted tests for the same intended use measuring the same or directly comparable analytes under this policy.

• Clinical validity (CV) of any analytes (or expression profiles) measured must be established through a study published in the peer-reviewed literature for the intended use of the test in the intended population. The degree of validity must be similar or superior to established and covered tests under this policy (see associated coverage Articles). If conducted with concordance to tissue histologic evaluation, the appropriate Banff Classification for renal allografts or other accepted criteria (if existing) must be used.

• The test is being used in a patient who is part of the population (disease and intended use) in which the test was analytically validated and has demonstrated CV.

• For a given patient encounter, only one molecular test for assessing allograft status may be performed. A test may include more than one assay; however, multianalyte and combination tests must demonstrate superiority and additive benefit when compared to respective single analytes or components.

• For minimally or non-invasive tests, the benefit to risk profile of the molecular test is considered by the ordering clinician to be more favorable than the benefit to risk profile of a tissue biopsy, or a tissue biopsy cannot be obtained, when the test and biopsy provide similar information. For example, this may be the case if a biopsy is considered medically contraindicated in a patient.

• The test successfully completes a MolDX Technical Assessment that will ensure that AV, CV, and clinical utility criteria set in this policy are met to establish the test as reasonable and necessary.

• A test and biopsy cannot be performed simultaneously. However, in very high-risk patients with overt signs and symptoms of rejection, a molecular test and biopsy may be performed together in urgent situations ONLY when the information derived from the test is complementary to the biopsy, established to meet CV requirements outlined above for that information, and demonstrated to improve outcomes in patients when performed along with biopsies. We expect these situations to be extremely rare.

Covered tests with AV that is significantly below similar services may have coverage rescinded.

Allograft solid-organ transplantation has become a standard of care in patients with end-stage organ disease. In some patients, these treatments, along with other advances in care, have transformed fatal disease into treatable and preventable disease.^1-3 Transplant patients are placed on immunosuppressant drug therapy and are routinely monitored for indicators of rejection to prolong the survival of the donor allograft. Serologic and laboratory markers aid in monitoring graft function and in the early detection of AR which may occur as ACR or AMR.⁴ Transplant recipients may also undergo (a) surveillance biopsies to detect subclinical acute rejection (subAR) and other histologic changes that precede functional allograft decline and/or (b) for-cause biopsies when clinically indicated. With early intervention, these changes may still be amenable to treatment. Early detection of AR has led to significant improvement in allograft survival in the first 12 months post-transplantation.^5,6

The importance of graft rejection and immunosuppression was discovered early on following the development of transplantation, a challenge that started to be overcome with the availability of immunosuppressants, though with the current standard-of-care for managing solid organ transplant patients, rejection remains a common problem with a high frequency of graft failure at 5 and 10 years.^6-9 Though organ transplant recipients remain at risk for rejection indefinitely, the risk is highest in the first year post-transplant.^10-12 Graft assessment is also used clinically to assist in the management of immunosuppression; the clinical value it brings is that it allows modification of immunosuppressive therapy to maximize graft longevity, which is a focus of post-transplant care. Histology has traditionally been used, often in conjunction with clinical and laboratory markers, as a common graft assessment tool.^9,13-19 While histology is considered the gold standard of diagnosis at this point in time, it requires a biopsy, which is invasive and may be associated with significant risks, complications and access to care barriers.

The interpretation of relevant histopathologic findings for the purpose of guiding management also poses a challenge. For example, in kidney transplantation, there has been heterogeneity in the literature regarding the definition and treatment of borderline and subAR, making it challenging to compare results between studies.^20-25 Borderline rejection is a heterogeneous diagnosis and includes the broad range of mild “inconsequential” inflammation to clinically significant ACR that can lead to inferior graft function.²⁴ Further, subAR can be detected in up to 25% of surveillance biopsies performed in the first year following kidney transplantation (a number that may be decreasing as immunosuppressive regimens improve); however, the clinical relevance of finding borderline and subAR has been uncertain for many years.^26-28 Nevertheless, it is now generally accepted that subAR is associated with worse graft outcomes ^{20,23,26,29-31} that may be improved with early diagnosis and treatment.^32,33 In a study from the University of Wisconsin, where donor specific antibody (DSA)-based protocol biopsies were performed at months 3 and 12 for kidney transplant recipients, patients with treated subclinical acute AMR were found to have similar good outcomes as those who underwent protocol biopsy but who were without rejection.³² The treated subAR patients also fared significantly better than those who underwent a clinically indicated biopsy with or without AMR.³² Another study from Johns Hopkins University evaluated kidney transplant recipients though year 5 post-transplantation and found no statistically significant difference in graft loss for patients with treated subclinical AMR compared to their matched controls; however patients with subclinical AMR who did not receive treatment had a 3.34-fold (95% CI: 1.37–8.11; p = 0.008) higher risk of graft loss.³³ Protocol biopsies in this study, which demonstrate value for renal surveillance testing, were performed at 1, 3, 6 and 12 months following ABO- and HLA-incompatible live donor transplants.³³

Despite evidence supporting its value, up to 80% of transplant centers do not routinely perform surveillance biopsies after kidney transplantation because of the relatively low incidence of subAR, the risk–benefit ratio of protocol biopsies and the fact that protocol biopsies have not definitively been shown to improve outcomes.^23,27,28,34 Further, the most current KDIGO guidelines on the management of kidney transplant recipients (published in 2009) also do not recommend surveillance biopsies.¹² For those centers that do perform surveillance biopsies, the surveillance biopsy testing schedules are not standardized.^23,27 The current care model for monitoring patients after kidney transplantation ranges from not using surveillance biopsies at all, to using them selectively in “high-immunologic risk” patients, to routine use in all patients.^27,30,32,35 Though there is no one standard of practice regarding the performance of surveillance biopsies in kidney transplantation, some center protocols have been published.^27,36

For other transplant types such as heart and lung, surveillance biopsies have traditionally been performed more frequently for the majority of patients, given the heightened risk of rejection early in the post-transplant period, though variations in surveillance biopsy practices and interpretive histopathologic challenges of biopsy apply to these transplant types as well.^10,37-42 For example, International Society for Heart and Lung Transplantation (ISHLT) guidelines suggest that approximately 13 endomyocardial biopsies (EMBs) (or other non-invasive methods) should be performed in the first 12 months following heart transplantation.¹⁰ However, the multicenter prospective cohort study from the Genomic Research Alliance for Transplantation (GRAfT) reported that heart transplant recipients underwent approximately 8 EMBs over a median follow-up time of 17.7 months.⁴¹

Molecular diagnostic methods have emerged in an attempt to address limitations in current diagnostics including the measurement of donor-derived cell-free DNA (cfDNA) and gene expression profile (GEP) assays, which have been developed for a number of organ allografts including kidney, heart, liver, and lung.^43-50 The principle underlying cfDNA assays to assess rejection is that the transplantation of a new organ involves transplantation of new genetic material, and genetic material is shed into the bloodstream as part of rejection.⁵¹ The fraction of cfDNA in the blood-stream may serve as a marker of rejection.^46-49 While this is a straightforward principle, DNA concentration in the bloodstream is quite small, and therefore tests relying on cfDNA require advanced technological methods that can accurately capture and quantify the presence of cfDNA specific to the allograft.^46,49,51 GEP tests tend to quantify expression of numerous genes in the allograft recipient and use these data in algorithms developed with sophisticated modeling or machine learning to determine whether rejection is occurring.^50,52 Molecular tests can not only provide information about graft status in a minimally-invasive manner, but they can be sensitive enough to be able to detect AR before it is evident histologically or by other clinical and laboratory indicators.^41,42,51 For example, in kidney transplant recipients, cfDNA values of 0.5% or more were associated with a nearly three-fold increase in risk of developing de novo DSAs; cfDNA was elevated a median of 91 days prior to DSA detection, suggesting a role for cfDNA as an early identifier of AR.^36,53 Further, for various transplant types, an improvement in cfDNA has been reported in patients who receive treatment for rejection and have biopsy evidence of resolution.^25,41,49

Circulating Donor-Derived Cell-Free DNA tests have also demonstrated the ability to identify subclinical recurrence in a surveillance setting. The Circulating Donor-Derived Cell-Free DNA in blood for diagnosing Acute Rejection in Kidney Transplant Recipients (DART) study by Bloom et. al demonstrated the performance of cfDNA in detecting allograft injury and AR; however, this study was not able to estimate the performance of cfDNA to discriminate AR in patients who may have had subclinical rejection because there were only 34 surveillance biopsies and only one finding of active rejection.⁴⁷ The Assessing Donor-derived cell-free DNA Monitoring Insights of kidney Allografts with Longitudinal surveillance (ADMIRAL) study by Bu et. al subsequently compared 45 surveilled patients with findings of AR on protocol biopsy with cfDNA findings.³⁶ This study found that elevation of cfDNA (≥0.5%) was significantly correlated with clinical and subclinical allograft rejection in kidney transplants and that persistently elevated cfDNA predicted over a 25% decline in the estimated glomerular filtration rate (eGFR) over three years.³⁶ Mantios et. al, who tested cfDNA at months 1, 2, 3, and 5 post-transplantation also found that in a surveillance group, high levels of cfDNA from the second month post-kidney transplantation were correlated with non-increasing eGFR one year post-transplantation; moreover, in patients with AR, levels of cfDNA decreased substantially after initiation of treatment.⁵⁴ In a recent study of 2,882 kidney allograft recipients from 14 transplantation centers in Europe and the United States, Aubert et. al found that the inclusion of cfDNA to a standard-of-care prediction model showed improved discrimination (area under the curve (AUC) 0.777 - 0.821; P = 0.0011); results were confirmed in external validation cohorts (n = 1,748).⁵⁵ Importantly, cfDNA was able to detect any kind of rejection, including subclinical rejection, which the authors note “remains the most challenging diagnosis when using traditional kidney transplant markers alone.”⁵⁵ There were no statistically significant differences in cfDNA levels between AMR and ACR and higher levels of cfDNA were associated with higher degrees of severity of both AMR and ACR.⁵⁵ Importantly, the authors found that the independent association of cfDNA with AR remained significant when cfDNA was tested in the first 3 months post-transplantation (OR = 2.370; 95% CI 1.505–3.730, P < 0.001), between 3 months and 1 year post-transplantation (OR = 1.882; 95% CI 1.381–2.566, P < 0.001) and after 1 year post-transplantation (OR = 2.521; 95% CI 1.944–3.316, P < 0.001).⁵⁵

Despite the fact that elevated cfDNA may be a predictor of AR and decreased eGFR, some kidney transplant recipients with elevated cfDNA remain clinically stable and it is not clear how to differentiate them from those who will develop adverse outcomes.⁵⁶ Further, cfDNA has been reported to have a limited sensitivity for detecting borderline and early ACR, raising concern that reliance on this analyte could miss cases of rejection (though AMR is thought to be the more important cause of transplant failure).⁵⁷ cfDNA also has a limited positive predictive value (PPV) (approximately 50-60%), suggesting that routine surveillance could potentially result in the performance of unnecessary biopsies, though this impact has not been observed in clinical utility studies to-date.⁵⁶ Nevertheless, many transplant programs in the United States are routinely surveilling kidney transplant patients with cfDNA and treating both subclinical AMR and ACR, despite the fact that there continues to be significant heterogeneity in the classification and treatment of subclinical borderline and early ACR.²² cfDNA tests have been proposed to reduce variance in interpretive approaches in order to better identify those patients with subclinical borderline and early ACR who are at elevated risk of graft injury.⁵⁸ In a retrospective single-center study of kidney transplant recipients, addition of cfDNA to Banff biopsy scores provided better prognostic assessment over certain biopsy findings alone.⁵⁹ However, that study was limited by a number of factors including the lack of standardized treatment protocols and the potential for bias introduced by exclusion of cfDNA tests assessed without a biopsy.⁵⁹

In heart transplantation, molecular biomarker testing has been used for over a decade and, unlike the outdated Banff guidelines for kidney transplantation (at the time of this work), the ISHLT guidelines do recommend the use of molecular biomarker testing in the evaluation of heart transplant recipients.^10,60 Despite longstanding clinical experience with Allomap (CareDx, Brisbane, CA), ISHLT guidelines affirm that the impact of GEP-guided surveillance on long-term clinical outcomes in heart transplantation still needs further study.¹⁰ Additionally, the optimal monitoring schedule using molecular methods is unknown, though ISHLT-recommended schedules for heart transplantation have been published for the performance of DSA and biopsy “or other non-invasive methods as appropriate.”¹⁰ In recent years, cfDNA testing has become more widely utilized in heart and lung transplant recipients as studies have shown good performance for the detection of AR. Studies evaluating cfDNA have shown high sensitivity (78.5%-81%), specificity (76.9%-85%) and NPV (97.3%-99.2%) for AR in heart transplant recipients.^41,61 Importantly, these studies also showed good performance for clinically significant ACR, previously thought to be better detected by GEP tests. Further, they have shown that cfDNA levels may rise weeks to months before AR is diagnosed on biopsy.^41,42,62-64 For example, in the GRAfT study, 80% of cfDNA elevations in heart transplant recipients were associated with a negative EMB.⁴¹ Importantly, the majority of these (76%) were considered clinically significant because they were associated with allograft dysfunction or preceded histopathologic rejection by up to 3.2 months.⁴¹ In lung transplant recipients, higher cfDNA values were associated with a significantly higher hazard of chronic lung allograft dysfunction (CLAD) or death than those with lower levels.⁶⁵ Moreover, during the COVID-19 pandemic, a home-based surveillance program using plasma cfDNA instead of surveillance bronchoscopy identified early episodes of AR and infection that would not have been identified using a clinically indicated biopsy strategy alone.⁴⁰ As a result, some heart and lung transplant centers have adopted cfDNA for surveillance alongside reduction in the number of biopsies during the first years post-transplantation, when the risk of AR is highest and when levels of molecular markers such as cfDNA are predictable.^{10,11,39,40,42,64,66}

Given the acceptance of GEP testing, studies subsequently attempted to evaluate the value of adding cfDNA to GEP in heart transplant patients, as both approaches were thought to have different strengths and weaknesses in ACR vs AMR detection.⁴² In a single-center retrospective review of combined GEP and cfDNA testing for AR surveillance, Gondi et. al found that combination testing at 6 months post-transplant resulted in the cancellation of 83.9% EMBs as opposed to 71.2% using a GEP-only surveillance approach.⁶⁷ This decrease was driven primarily by the 87 GEP (+) and cfDNA (-) results that would have previously resulted in an EMB but were reassigned to a lower risk group with the addition of cfDNA. Notably, there were very few rejections in the cohort (two AMR and two grade 2 ACR), and cfDNA detected them all while GEP missed the cases with AMR.⁶⁷ Another single center, retrospective analysis by Henricksen et. al found that at one year post transplantation, there were no differences between the paired testing and GEP-only cohorts in terms of survival or rejection-free survival, though paired testing was associated with fewer EMBs. However, their study only had 3 episodes of clinically significant AR and there was not a standard protocol for reacting to the results of the noninvasive surveillance.⁶⁸ In a retrospective observational study of more than 400 samples from 112 unique heart transplant patients who underwent combination testing with both cfDNA and GEP, Rodgers et. al observed a significantly improved specificity without a significant change in sensitivity when using cfDNA instead of a combination testing approach (sensitivity: 36.8% cfDNA vs 50.5% combination testing, p=0.99; specificity: 86.3% cfDNA vs 46.8% combination testing, p < 0.0001); this study identified 13 samples associated with AR, 10 of which were ACR.⁶⁹ Based on their findings, the authors conclude that cfDNA testing without GEP is sufficient, agreeing with other reports that cfDNA alone has the potential to replace or significantly reduce the need for EMB.^{41,42,61,62,69} A prospective cohort study of 565 plasma samples collected longitudinally from 65 adult and pediatric transplant recipients also reported that cfDNA showed superior test performance when compared to AlloMap [AUC cfdDNA = 0.83; AUC AlloMap = 0.72];⁶² notably, they compared the performance of cfDNA from their study with that of AlloMap as reported in another study by Deng et. al.⁷⁰ Finally, the performance of combination testing for ACR surveillance was evaluated most recently in the Surveillance HeartCare Outcomes Registry (SHORE) study.⁷¹ The reported sensitivity, specificity, and likelihood ratio (LR) for combination testing was 32.3%, 91.7% and 3.90 (95% CI: 3.08-4.96); sensitivities, specificities and LRs for testing with GEP alone were 59%, 56.8% and 1.37 (95% CI: 1.20-1.56) and 44.7%, 84.6% and 2.91 (95% CI: 2.43-3.49) for cfDNA alone.⁷¹ Of the 156 grade 2 ACR events reported, only 31.4% were dual positive (49/156) while another 30% were dual negative (46/156) by molecular testing.⁷¹ The incidence of ACR in the GEP negative/ cfDNA negative group (1.5%; 95% CI: 1.1%-2.0%) was not significantly different from that of the GEP positive/cfDNA negative group (1.9%; 95% CI: 1.4%- 2.6%); however, in the GEP negative/ cfDNA positive and dual positive groups it was 4.3% (95% CI: 2.8%-6.6%) and 9.2% (95% CI: 7.1%-11.9%), respectively.⁷¹ Of the cfDNA positive tests (n=1026), 72 (7%) showed clinically significant ACR, similar to the dual positive tests. Notably, ACR was observed most frequently in the first 30 days post-transplant.

There is considerably limited evidence for combination testing using cfDNA and GEP in kidney transplantation.^72,73 For this reason, the American Society of Transplant Surgeons (ASTS) and the European Society of Organ Transplantation (including expert members from the United States) also do not support GEP or combination testing for this indication.^74,75

Just as there is no one standard of practice regarding the performance of surveillance biopsies, particularly in kidney transplantation, there is also not a standard practice for the performance of surveillance molecular tests, though some center protocols have been published in the literature.^36,76 Questions remain regarding which patients would benefit most from routine serial testing, how often to test, and the appropriate steps to further evaluate an elevated cfDNA.^25,77 Minimally invasive testing should “allow for a biomarker stratified approach for those at a higher risk of harboring subAR.”³⁰

Importantly, these molecular tests are not meant to be used in isolation. Rather, they are part of a constellation of clinico-laboratory data used to evaluate the patient.⁵⁷ Accordingly, the 2022 Banff-Canadian Society of Transplantation Joint Meeting and the Banff Minimally Invasive Diagnostics Working Group have concluded that these biomarkers should not be used alone to monitor patients in the setting of stable allograft function.^57,78

While these technologies are newer, large and multicenter studies have supported their use in renal, heart, and lung transplantation as minimally and non-invasive methods to assess allograft status, modify immunosuppression regimens, and avoid unnecessary biopsies.^{11,40,46,47,50} Evidence continues to develop for other transplant allograft organs and other analytes.^45,79-82

Contractor Advisory Committee (CAC) Summary

Kidney and Liver Allograft CAC

On November 16, 2022, Noridian and Palmetto jointly facilitated a CAC to discuss molecular testing for the diagnosis of acute rejection in kidney or liver transplant recipients where GEP, cfDNA, and multiomic tests were discussed. The subject matter experts (SMEs) expressed a high degree of certainty that there is sufficient evidence to support the use of molecular tests like cfDNA in kidney allograft patients.

Heart and Lung Allograft CAC

On November 17, 2022, Noridian and Palmetto jointly facilitated a CAC to discuss molecular testing for the diagnosis of acute rejection in heart or lung transplant recipients where GEP and cfDNA tests were discussed. The SMEs were unanimous that the evidence is sufficient to support the use of GEP and/or cfDNA for surveillance of acute organ injury to help replace an unnecessary biopsy. However, they also agreed that there is a lack of data to support the routine use of molecular combination testing. Moreover, they did not endorse the use of molecular diagnostic tests in lieu of biopsy in patients with a very high clinical and laboratory suspicion for acute rejection and who can also safely tolerate a biopsy. All SMEs agreed that these tests do not discern the etiology of organ injury, indicating that they had a high degree of confidence in the detection of allograft injury, but additional clinical testing was necessary to discern the cause.

Documents associated with the CAC meetings can be found here:

Contractor Advisory Committee (CAC) - JE Part B - Noridian (noridianmedicare.com)

Graft assessment is a well-accepted part of solid organ transplant management. Evidence clearly shows that patients are living with functioning organs transplanted from immunologically and genetically distinct individuals using current transplant management techniques, which may demonstrate significant heterogeneity among centers or even among individual physicians. For example, the CAC SMEs acknowledged that only approximately 18% of transplant centers perform routine surveillance biopsies in kidney transplant patients, because the evidence on the benefit of that practice is conflicting. Similarly, some centers have moved away from performing protocol biopsies in other transplant types due to the highly invasive nature of the procedures and the high risk of complications.

It is also well accepted within the transplant community that the management of immunosuppression is an important component of post-transplant care to both optimize graft longevity while avoiding side effects and toxicity of immunosuppressive therapies. Graft assessment is an important decision tool used to help clinicians optimize immunosuppressive treatment. The gold standard for assessing rejection or injury has historically been and remains a biopsy in conjunction with clinical and laboratory criteria. However, given the invasive nature and risks associated with a biopsy, tests that can potentially mitigate the need for a biopsy while still providing clinicians with actionable information that can be used to help optimize immunosuppressive therapy are reasonable and necessary. Additionally, studies have supported that cfDNA and GEP can accurately determine allograft status in several organ types, and that molecular characterization can both precede and enhance histologic and other laboratory findings of AR. As such, these approaches, as a service type, are reasonable and necessary for graft assessment.

Optimal outcomes of the use of molecular biomarkers in the context of allograft rejection monitoring include the reduction in the number of overall and negative biopsies and the accurate detection and exclusion of AR and subAR. Potential risks of using these biomarkers include missing subAR (particularly subclinical ACR) or other causes of graft injury and, on the other side, subjecting patients to the unnecessary risks of a negative surveillance biopsy because of a false positive result. Nevertheless, the evidence to-date has not shown an increase in such negative early outcomes. Rather, reports have shown that these tests can safely obviate the need for invasive biopsy in many cases. Further, the sensitivity of some of these molecular tests (i.e., cfDNA in heart transplantation) for the early detection of rejection events has challenged the gold-standard status of the biopsy altogether.

This contractor recognizes the newer literature supporting the use of surveillance biopsies as well as molecular testing for surveillance to identify subclinical rejection and allow for early intervention, even where surveillance using biopsy for the same purpose might not be worth the attendant risk and morbidity. However, the optimal interval of surveillance monitoring with molecular tests has not been defined for any transplant type and prospective studies are still ongoing to assess the impact of serial cfDNA surveillance in transplant recipients. An additional challenge is the wide variability in practice among transplant centers. Physicians know best how to manage the care of their patients. However, as a Medicare Administrative Contractor (MAC), we are required by statute to provide coverage for and reimburse services determined to be reasonable and necessary (R&N) according to the published medical evidence. As such, this contractor will issue coverage for molecular tests used for the purpose of surveillance according to a cadence that is R&N based on the prevalence of acute rejection for a given transplant type as well as the available (albeit limited) evidence on outcomes associated with surveillance testing approaches. There are several publications on surveillance testing, some of which include molecular tests or combined methodologies. For kidney transplantation, publications that have demonstrated improved outcomes as a result of surveillance testing included no more than 4 testing timepoints in the first-year post-transplantation. Though some publications (including DART) have performed testing exceeding this number, there is no evidence to suggest, nor is it a reasonable assumption, that those extra tests provided any additional clinical benefit. A similar logic follows for other covered transplant types such as heart and lung, for which the maximum allowable surveillance test limit is twelve in the first year post transplantation.^10,39-42 After the first year, surveillance testing may continue at a decreased frequency, as supported by evidence of analyte predictability and improved patient outcomes.^10,40,42,83 Given the limited but evolving evidence, molecular surveillance testing for allograft rejection is considered by this contractor to be a service comprised of multiple timepoint assays with evidence to support it as R&N. Should national consensus guidelines be generated to demonstrate that a cfDNA (or other molecular biomarker) could improve outcomes at a different schedule or with a different number of testing timepoints comprising the service, these altered schedules would be compliant with this policy without need for amendment as it would fulfill existing coverage requirements listed above.

Although the use of combined GEP and cfDNA testing in heart transplant patients has been previously covered and broadly used, it should be noted that initial coverage was set without supporting peer reviewed published evidence and, at this time in review of existing evidence, there is insufficient compelling evidence to support the routine use of molecular combination testing (i.e. with cfDNA and GEP) for any transplant type as the data support that cfDNA testing may be superior to GEP and any value from combined testing appears to be derived from benefits of cfDNA alone. While the ASTS position statement does support combination testing (in heart transplantation only), it does not supply compelling evidence of improved patient outcomes to support this recommendation.⁷⁴ Most of the studies that evaluated combination testing with both biomarkers compared that approach with testing by GEP alone. Some of those studies (such as the ones by Gondi et. al and Henricksen et. al) had very few episodes of AR and were underpowered to draw meaningful conclusions regarding an outcomes-based benefit from combination testing. Further, these studies failed to consider that testing by cfDNA alone could provide a superior alternative to GEP, though their data was consistent with this interpretation. This conclusion was also supported by other studies including Rodgers et. al who showed a decrease in specificity with no change in sensitivity or NPV when GEP was added to cfDNA testing for heart transplant recipients. cfDNA was also the apparent driver of improved performance in the SHORE registry study as the GEP-positive/ cfDNA-negative group did not perform any better than the dual negative group. Additionally, combination testing still missed the majority of ACRs (sensitivity was only 33%) without any clear benefit in specificity when compared to cfDNA alone. Of note, the prevalence of AR was highest in the first 30 days, making predictive values very different early versus later in the study, particularly when GEP is also not validated for use prior to 55 days post-transplant.

Studies evaluating cfDNA alone have shown high sensitivity, specificity and NPV for AR as well as ACR in heart transplant recipients; further, they have also shown that cfDNA can detect clinically significant but histologically silent allograft injury.^41,42,61-64 These studies affirm that cfDNA can independently and significantly reduce the need for surveillance biopsies, and potentially replace such biopsies altogether. In sum, the evidence developed shows that cfDNA is, at a minimum, non-inferior to GEP for the detection of allograft injury and rejection and that the addition of GEP to cfDNA does not provide additional value; none of the papers reviewed contradict this. Though GEP will continue to be covered in heart transplantation only as it has become a standard of practice, providers should be aware that they may be performing an inferior service. Should evolving literature clearly support cfDNA as superior to GEP for non-invasive testing in heart transplantation and demonstrate no clear value for GEP testing, this coverage decision will be modified to reflect the new evidence.

Non-invasive graft assessment remains an actively evolving area of medicine as does the assessment of graft rejection via histology. As such, this contractor will continue to monitor new evidence that may impact this coverage decision.

1. The United States Renal Data System (USRDS) 2021 Annual Data Report (ADR). https://usrds-adr.niddk.nih.gov/2021/end-stage-renal-disease/7-transplantation. Accessed 1/3/2025.
2. Ponikowski P, Voors AA, Anker SD, et al. 2016 ESC guidelines for the diagnosis and treatment of acute and chronic heart failure: the Task Force for the diagnosis and treatment of acute and chronic heart failure of the European Society of Cardiology (ESC). Developed with the special contribution of the Heart Failure Association (HFA) of the ESC. Eur J Heart Fail. 2016;18(8):891-975. doi:10.1002/ejhf.592
3. Yancy CW, Jessup M, Bozkurt B, et al. 2013 ACCF/AHA guideline for the management of heart failure: a report of the American College of Cardiology Foundation/American Heart Association Task Force on practice guidelines. J Am Coll Cardiol. 2013;62(16):e147-e239. doi:10.1016/j.jacc.2013.05.019
4. McManigle W, Pavlisko EN, Martinu T. Acute cellular and antibody-mediated allograft rejection. Semin Respir Crit Care Med. 2013;34(3):320-335. doi:10.1055/s-0033-1348471
5. Serón D, Arns W, Chapman JR. Chronic allograft nephropathy—clinical guidance for early detection and early intervention strategies. Nephrol Dial Transplant. 2008;23(8):2467-2473. doi:10.1093/ndt/gfn130
6. Lamb KE, Lodhi S, Meier-Kriesche HU. Long-term renal allograft survival in the United States: a critical reappraisal. Am J Transplant. 2011;11(3):450-462. doi:10.1111/j.1600-6143.2010.03283.x
7. United States Government Accountability Office. End-Stage Renal Disease: Characteristics of Kidney Transplant Recipients, Frequency of Transplant Failures, and Cost to Medicare. GAO-07-1117. Published: 2007.
8. Stegall MD, Gaston RS, Cosio FG, Matas A. Through a glass darkly: seeking clarity in preventing late kidney transplant failure. J Am Soc Nephrol. 2015;26(1):20-29. doi:10.1681/asn.2014040378
9. Stehlik J, Kobashigawa J, Hunt SA, Reichenspurner H, Kirklin JK. Honoring 50 years of clinical heart transplantation in Circulation: in-depth state-of-the-art review. Circulation. 2018;137(1):71-87. doi:10.1161/circulationaha.117.029753
10. Velleca A, Shullo MA, Dhital K, et al. The International Society for Heart and Lung Transplantation (ISHLT) guidelines for the care of heart transplant recipients. J Heart Lung Transplant. 2023;42(5):e1-e141. doi:10.1016/j.healun.2022.10.015
11. Khush KK, Patel J, Pinney S, et al. Noninvasive detection of graft injury after heart transplant using donor-derived cell-free DNA: a prospective multicenter study. Am J Transplant. 2019;19(10):2889-2899. doi:10.1111/ajt.15339
12. Kidney Disease: Improving Global Outcomes (KDIGO) Transplant Work Group. KDIGO clinical practice guideline for the care of kidney transplant recipients. Am J Transplant. 2009;9 Suppl 3:S1-S155. doi:10.1111/j.1600-6143.2009.02834.x
13. Haas M, Loupy A, Lefaucheur C, et al. The Banff 2017 Kidney Meeting Report: revised diagnostic criteria for chronic active T cell-mediated rejection, antibody-mediated rejection, and prospects for integrative endpoints for next-generation clinical trials. Am J Transplant. 2018;18(2):293-307. doi:10.1111/ajt.14625
14. Solez K, Axelsen RA, Benediktsson H, et al. International standardization of criteria for the histologic diagnosis of renal allograft rejection: the Banff working classification of kidney transplant pathology. Kidney Int. 1993;44(2):411-422. doi:10.1038/ki.1993.259
15. Bruneval P, Angelini A, Miller D, et al. The XIIIth Banff Conference on Allograft Pathology: The Banff 2015 Heart Meeting Report: improving antibody-mediated rejection diagnostics: strengths, unmet needs, and future directions. Am J Transplant. 2017;17(1):42-53. doi:10.1111/ajt.14112
16. Stewart S, Fishbein MC, Snell GI, et al. Revision of the 1996 working formulation for the standardization of nomenclature in the diagnosis of lung rejection. J Heart Lung Transplant. 2007;26(12):1229-1242. doi:10.1016/j.healun.2007.10.017
17. Stewart S, Winters GL, Fishbein MC, et al. Revision of the 1990 working formulation for the standardization of nomenclature in the diagnosis of heart rejection. J Heart Lung Transplant. 2005;24(11):1710-1720. doi:10.1016/j.healun.2005.03.019
18. Mehra MR. Heart transplantation at 50. Lancet. 2017;390(10111):e43-e45. doi:10.1016/s0140-6736(17)33093-3
19. Nankivell BJ, Alexander SI. Rejection of the kidney allograft. N Engl J Med. 2010;363(15):1451-1462. doi:10.1056/NEJMra0902927
20. Seifert ME, Agarwal G, Bernard M, et al. Impact of subclinical borderline inflammation on kidney transplant outcomes. Transplant Direct. 2021;7(2):e663. doi:10.1097/txd.0000000000001119
21. Seron D, Rabant M, Becker JU, et al. Proposed definitions of T cell-mediated rejection and tubulointerstitial inflammation as clinical trial endpoints in kidney transplantation. Transpl Int. 2022;35:10135. doi:10.3389/ti.2022.10135
22. Loupy A, Haas M, Roufosse C, et al. The Banff 2019 Kidney Meeting Report (I): updates on and clarification of criteria for T cell- and antibody-mediated rejection. Am J Transplant. 2020;20(9):2318-2331. doi:10.1111/ajt.15898
23. Rush DN, Gibson IW. Subclinical inflammation in renal transplantation. Transplantation. 2019;103(6):e139-e145. doi:10.1097/TP.0000000000002682
24. Nankivell BJ, Agrawal N, Sharma A, et al. The clinical and pathological significance of borderline T cell-mediated rejection. Am J Transplant. 2019;19(5):1452-1463. doi:10.1111/ajt.15197
25. Gupta G, Moinuddin I, Kamal L, et al. Correlation of donor-derived cell-free DNA with histology and molecular diagnoses of kidney transplant biopsies. Transplantation 2022;106(5):1061-1070. doi:10.1097/tp.0000000000003838
26. Naesens M, Friedewald J, Mas V, Kaplan B, Abecassis MM. A practical guide to the clinical implementation of biomarkers for subclinical rejection following kidney transplantation. Transplantation. 2020;104(4):700-707. doi:10.1097/TP.0000000000003064
27. Mehta R, Cherikh W, Sood P, Hariharan S. Kidney allograft surveillance biopsy practices across US transplant centers: a UNOS survey. Clin Transplant. 2017;31(5):10.1111/ctr.12945. doi:10.1111/ctr.12945
28. Rush D, Arlen D, Boucher A, et al. Lack of benefit of early protocol biopsies in renal transplant patients receiving TAC and MMF: a randomized study. Am J Transplant. 2007;7(11):2538-45. doi:10.1111/j.1600-6143.2007.01979.x
29. Ortiz F, Gelpi R, Helanterä I, et al. Decreased kidney graft survival in low immunological risk patients showing inflammation in normal protocol biopsies. PLoS One. 2016;11(8):e0159717. doi:10.1371/journal.pone.0159717
30. Friedewald JJ, Kurian SM, Heilman RL, et al. Development and clinical validity of a novel blood-based molecular biomarker for subclinical acute rejection following kidney transplant. Am J Transplant. 2019;19(1):98-109. doi:10.1111/ajt.15011
31. Mehta R, Bhusal S, Randhawa P, et al. Short-term adverse effects of early subclinical allograft inflammation in kidney transplant recipients with a rapid steroid withdrawal protocol. Am J Transplant. 2018;18(7):1710-1717. doi:10.1111/ajt.14627
32. Parajuli S, Joachim E, Alagusundaramoorthy S, et al. Subclinical antibody-mediated rejection after kidney transplantation: treatment outcomes. Transplantation. 2019;103(8):1722-1729. doi:10.1097/tp.0000000000002566
33. Orandi BJ, Chow EHK, Hsu A, et al. Quantifying renal allograft loss following early antibody-mediated rejection. Am J Transplant. 2015;15(2):489-498. doi:10.1111/ajt.12982
34. Lee DM, Abecassis MM, Friedewald JJ, Rose S, First MR. Kidney graft surveillance biopsy utilization and trends: results from a survey of high-volume transplant centers. Transplant Proc. 2020;52(10):3085-3089. doi:10.1016/j.transproceed.2020.04.1816
35. Naesens M. The special relativity of noninvasive biomarkers for acute rejection. Am J Transplant. 2019;19(1):5-8. doi:10.1111/ajt.15078
36. Bu L, Gupta G, Pai A, et al. Clinical outcomes from the assessing donor-derived cell-free DNA monitoring insights of kidney allografts with longitudinal surveillance (ADMIRAL) study. Kidney Int. 2022;101(4):793-803. doi:10.1016/j.kint.2021.11.034
37. Goldberg JF, Truby LK, Agbor-Enoh S, et al. Selection and interpretation of molecular diagnostics in heart transplantation. Circulation. 2023;148(8):679-694. doi:10.1161/circulationaha.123.062847
38. Parulekar AD, Kao CC. Detection, classification, and management of rejection after lung transplantation. J Thorac Dis. 2019;11(Suppl 14):S1732-S1739. doi:10.21037/jtd.2019.03.83
39. Martinu T, Koutsokera A, Benden C, et al. International Society for Heart and Lung Transplantation consensus statement for the standardization of bronchoalveolar lavage in lung transplantation. J Heart Lung Transplant. 2020;39(11):1171-1190. doi:10.1016/j.healun.2020.07.006
40. Keller M, Sun J, Mutebi C, et al. Donor-derived cell-free DNA as a composite marker of acute lung allograft dysfunction in clinical care. J Heart Lung Transplant. 2022;41(4):458-466. doi:10.1016/j.healun.2021.12.009
41. Agbor-Enoh S, Shah P, Tunc I, et al. Cell-free DNA to detect heart allograft acute rejection. Circulation. 2021;143(12):1184-1197. doi:10.1161/circulationaha.120.049098
42. Holzhauser L, DeFilippis EM, Nikolova A, et al. The end of endomyocardial biopsy?: A practical guide for noninvasive heart transplant rejection surveillance. JACC Heart Fail. 2023;11(3):263-276. doi:10.1016/j.jchf.2022.11.002
43. Rosenheck JP, Ross DJ, Botros M, et al. Clinical validation of a plasma donor-derived cell-free DNA assay to detect allograft rejection and injury in lung transplant. Transplant Direct. 2022;8(4):e1317. doi:10.1097/txd.0000000000001317
44. Richmond ME, Zangwill SD, Kindel SJ, et al. Donor fraction cell-free DNA and rejection in adult and pediatric heart transplantation. J Heart Lung Transplant. 2020;39(5):454-463. doi:10.1016/j.healun.2019.11.015
45. Levitsky J, Asrani SK, Schiano T, et al. Discovery and validation of a novel blood-based molecular biomarker of rejection following liver transplantation. Am J Transplant. 2020;20(8):2173-2183. doi:10.1111/ajt.15953
46. Sigdel TK, Archila FA, Constantin T, et al. Optimizing detection of kidney transplant injury by assessment of donor-derived cell-free DNA via massively multiplex PCR. J Clin Med. 2018;8(1):19. doi:10.3390/jcm8010019
47. Bloom RD, Bromberg JS, Poggio ED, et al. Cell-free DNA and active rejection in kidney allografts. J Am Soc Nephrol. 2017;28(7):2221-2232. doi:10.1681/asn.2016091034
48. Bromberg JS, Brennan DC, Poggio E, et al. Biological variation of donor-derived cell-free DNA in renal transplant recipients: clinical implications. J Appl Lab Med. 2017;2(3):309-321. doi:10.1373/jalm.2016.022731
49. Grskovic M, Hiller DJ, Eubank LA, et al. Validation of a clinical-grade assay to measure donor-derived cell-free DNA in solid organ transplant recipients. J Mol Diagn. 2016;18(6):890-902. doi:10.1016/j.jmoldx.2016.07.003
50. Marsh CL, Kurian SM, Rice JC, et al. Application of TruGraf v1: a novel molecular biomarker for managing kidney transplant recipients with stable renal function. Transplant Proc. 2019;51(3):722-728. doi:10.1016/j.transproceed.2019.01.054
51. Beck J, Oellerich M, Schulz U, et al. Donor-derived cell-free DNA is a novel universal biomarker for allograft rejection in solid organ transplantation. Transplant Proc. 2015;47(8):2400-2403. doi:10.1016/j.transproceed.2015.08.035
52. Kurian SM, Velazquez E, Thompson R, et al. Orthogonal comparison of molecular signatures of kidney transplants with subclinical and clinical acute rejection: equivalent performance is agnostic to both technology and platform. Am J Transplant. 2017;17(8):2103-2116. doi:10.1111/ajt.14224
53. Mayer KA, Doberer K, Tillgren A, et al. Diagnostic value of donor-derived cell-free DNA to predict antibody-mediated rejection in donor-specific antibody-positive renal allograft recipients. Transpl Int. 2021;34(9):1689-1702. doi:10.1111/tri.13970
54. Mantios E, Filiopoulos V, Constantoulakis P, et al. Assessment of donor derived cell free DNA (dd-cfDNA) at surveillance and at clinical suspicion of acute rejection in renal transplantation. Transpl Int. 2023;36:11507. doi:10.3389/ti.2023.11507
55. Aubert O, Ursule-Dufait C, Brousse R, et al. Cell-free DNA for the detection of kidney allograft rejection. Nat Med. 2024;30(8)2320-2327. doi:10.1038/s41591-024-03087-3
56. Huang E, Haas M, Gillespie M, et al. An assessment of the value of donor-derived cell-free DNA surveillance in patients with preserved kidney allograft function. Transplantation. 2023;107(1):274-282. doi:10.1097/tp.0000000000004267
57. Huang E, Mengel M, Clahsen-van Groningen MC, Jackson AM. Diagnostic potential of minimally invasive biomarkers: a biopsy-centered viewpoint from the Banff Minimally Invasive Diagnostics Working Group. Transplantation. 2023;107(1):45-52. doi:10.1097/tp.0000000000004339
58. Stites E, Kumar D, Olaitan O, et al. High levels of dd-cfDNA identify patients with TCMR 1A and borderline allograft rejection at elevated risk of graft injury. Am J Transplant. 2020;20(9):2491-2498. doi:10.1111/ajt.15822
59. Huang E, Gillespie M, Ammerman N, et al. Donor-derived cell-free DNA combined with histology improves prediction of estimated glomerular filtration rate over time in kidney transplant recipients compared with histology alone. Transplant Direct. 2020;6(8):e580. doi:10.1097/txd.0000000000001027
60. Pham MX, Teuteberg JJ, Kfoury AG, et al. Gene-expression profiling for rejection surveillance after cardiac transplantation. N Engl J Med. 2010;362(20):1890-900. doi:10.1056/NEJMoa0912965
61. Kim PJ, Olymbios M, Siu A, et al. A novel donor-derived cell-free DNA assay for the detection of acute rejection in heart transplantation. J Heart Lung Transplant. 2022;41(7):919-927. doi:10.1016/j.healun.2022.04.002
62. De Vlaminck I, Valantine HA, Snyder TM, et al. Circulating cell-free DNA enables noninvasive diagnosis of heart transplant rejection. Sci Transl Med. 2014;6(241):241ra77. doi:10.1126/scitranslmed.3007803
63. Jang MK, Tunc I, Berry GJ, et al. Donor-derived cell-free DNA accurately detects acute rejection in lung transplant patients, a multicenter cohort study. J Heart Lung Transplant. 2021;40(8):822-830. doi:10.1016/j.healun.2021.04.009
64. Keller M, Agbor-Enoh S. Donor-derived cell-free DNA for acute rejection monitoring in heart and lung transplantation. Curr Transplant Rep. 2021;8(4):351-358. doi:10.1007/s40472-021-00349-8
65. Agbor-Enoh S, Wang Y, Tunc I, et al. Donor-derived cell-free DNA predicts allograft failure and mortality after lung transplantation. EBioMedicine. 2019;40:541-553. doi:10.1016/j.ebiom.2018.12.029
66. Keller M, Agbor-Enoh S. Cell-free DNA in lung transplantation: research tool or clinical workhorse? Curr Opin Organ Transplant. 2022;27(3):177-183. doi:10.1097/mot.0000000000000979
67. Gondi KT, Kao A, Linard J, et al. Single-center utilization of donor-derived cell-free DNA testing in the management of heart transplant patients. Clin Transplant. 2021;35(5):e14258. doi:10.1111/ctr.14258
68. Henricksen EJ, Moayedi Y, Purewal S, et al. Combining donor derived cell free DNA and gene expression profiling for non-invasive surveillance after heart transplantation. Clin Transplant. 2023;37(3):e14699. doi:10.1111/ctr.14699
69. Rodgers N, Gerding B, Cusi V, et al. Comparison of two donor-derived cell-free DNA tests and a blood gene-expression profile test in heart transplantation. Clin Transplant. 2023;37(6):e14984. doi:10.1111/ctr.14984
70. Deng MC, Eisen HJ, Mehra MR, et al. Noninvasive discrimination of rejection in cardiac allograft recipients using gene expression profiling. Am J Transplant. 2006;6(1):150-160. doi:10.1111/j.1600-6143.2005.01175.x
71. Khush K, Hall S, Kao A, et al. Surveillance with dual noninvasive testing for acute cellular rejection after heart transplantation: outcomes from the Surveillance HeartCare Outcomes Registry. J Heart Lung Transplant. 2024;43(9):1409-1421. doi:10.1016/j.healun.2024.05.003
72. Park S, Guo K, Heilman RL, et al. Combining blood gene expression and cellfree DNA to diagnose subclinical rejection in kidney transplant recipients. Clin J Am Soc Nephrol. 2021;16(10):1539-1551. doi:10.2215/cjn.05530421
73. Cheung R, Xu H, Jin X, et al. Validation of a gene expression signature to measure immune quiescence in kidney transplant recipients in the CLIA setting. Biomark Med. 2022;16(8):647-661. doi:10.2217/bmm-2022-0113
74. American Society of Transplant Surgeons (ASTS) Executive Committee. 2024. ASTS Statement on donor-derived cell-free DNA (dd-cfDNA). American Society of Transplantation. Published 2023; Updated 2024. https://www.asts.org/docs/default-source/position-statements/asts-statement-on-donor-derived-cell-free-dna-(dd-cfdna)—-updated-oct.-2024.pdf?sfvrsn=19314fd3_3. Accessed 1/3/2025.
75. Park S, Sellares J, Tinel C, Anglicheau D, Bestard O, Friedewald JJ. European Society of Organ Transplantation Consensus Statement on testing for non-invasive diagnosis of kidney allograft rejection. Transpl Int. 2024;36:12115. doi:10.3389/ti.2023.12115
76. Pai A, Swan JT, Wojciechowski D, et al. Clinical rationale for a routine testing schedule using donor-derived cell-free DNA after kidney transplantation. Ann Transplant. 2021;26:e932249. doi:10.12659/aot.932249
77. Gupta G, Tanriover B. Donor-derived cell-free DNA measurement in kidney transplant patients without allograft dysfunction: more evidence and more questions. Transplantation. 2023;107(1):25-26. doi:10.1097/tp.0000000000004268
78. Carrigan I, Mathur S, Bourgeois N, et al. Updates in kidney transplantation from the 2022 Banff-Canadian Society of Transplantation Joint Meeting: conference report. Can J Kidney Health Dis. 2023;10:20543581231209185. doi:10.1177/20543581231209185
79. Sigdel T, Nguyen M, Liberto J, et al. Assessment of 19 genes and validation of CRM gene panel for quantitative transcriptional analysis of molecular rejection and inflammation in archival kidney transplant biopsies. Front Med (Lausanne). 2019;6:213. doi:10.3389/fmed.2019.00213
80. Schütz E, Fischer A, Beck J, et al. Graft-derived cell-free DNA, a noninvasive early rejection and graft damage marker in liver transplantation: a prospective, observational, multicenter cohort study. PLoS Med. 2017;14(4):e1002286. doi:10.1371/journal.pmed.1002286
81. Guzzi F, Cirillo L, Buti E, et al. Urinary biomarkers for diagnosis and prediction of acute kidney allograft rejection: a systematic review. Int J Mol Sci. 2020;21(18):6889. doi:10.3390/ijms21186889
82. Adam B, Afzali B, Dominy KM, et al. Multiplexed color-coded probe-based gene expression assessment for clinical molecular diagnostics in formalin-fixed paraffin-embedded human renal allograft tissue. Clin Transplant. 2016;30(3):295-305. doi:10.1111/ctr.12689
83. Chen CC, Lin WC, Lee CY, Yang CY, Tsai MK. Two-year protocol biopsy after kidney transplantation in clinically stable recipients - a retrospective study. Transpl Int. 2021;34(1):185-193. doi:10.1111/tri.13785

• Provider Education/Guidance

• Solid Organ Allograft Rejection