The Clinical Relevance of the Infiltrating Immune Cell Composition in Kidney Transplant Rejection

BACKGROUND

The link between the histology of kidney transplant rejection, especially Antibody-mediated rejection, T cell-mediated rejection and Mixed rejection, and the types of infiltrating immune cells is currently not well charted. Cost and technical complexity of single cell analysis hinder large scale studies of the relationship between cell infiltrate profiles and histological heterogeneity.

METHODS

In this cross-sectional study, we assessed the composition of nine intragraft immune cell types by using a validated kidney transplant-specific signature matrix for deconvolution of bulk transcriptomics in three different kidney transplant biopsy datasets (N=403, N=224, N=282). The association and the discrimination of the immune cell types with the Banff histology and the association with graft failure were assessed individually and with multivariable models. Unsupervised clustering algorithms were applied on the overall immune cells composition and compared to the Banff phenotypes.

RESULTS

Banff-defined rejection was related to high presence of CD8+ effector T cells, Natural Killer cells, monocytes/macrophages and to a lesser extent B cells, whereas CD4+ memory T cells were lower in rejection compared to no rejection. Estimated intragraft effector memory-expressing CD45RA (TEMRA) CD8+ T cells were strongly and consistently associated with graft failure. The large heterogeneity in immune cell composition across rejection types prevented supervised and unsupervised methods to accurately recover the Banff phenotypes based solely on immune cell estimates. The lack of correlation between immune cell composition and Banff-defined rejection types was validated using multiplex immunohistochemistry.

CONCLUSIONS

Although some specific cell types (FCGR3A+ myeloid cells, CD14+ monocytes/macrophages and NK cells), partly discriminate between rejection phenotypes, the overall estimated immune cell composition of kidney transplants is ill related to main Banff-defined rejection categories and adds to the Banff lesion scoring and evaluation of rejection severity. The estimated intragraft CD8temra cells bear strong and consistent association with graft failure and independent of Banff-grade rejection.

The role of exercise training on cardiovascular risk factors and heart disease in patients with chronic kidney disease G3-G5 and G5D: A Clinical Consensus Statement of the European Association of Preventive Cardiology (EAPC) of the ESC and the European Association of Rehabilitation in Chronic Kidney Disease (EURORECKD)

Cardiovascular (CV) morbidity and mortality is high in patients with chronic kidney disease (CKD). Most patients reveal a high prevalence of CV risk factors such as diabetes or arterial hypertension and many have manifest cardiovascular disease (CVD), such as coronary artery disease and chronic heart failure with an increased risk of clinical events including sudden cardiac death. Diabetes mellitus and hypertension contribute to the development of CKD and the prevalence of CKD is in the range of 20%-65% in diabetic and 30%-50% in hypertensive patients. Therefore, prevention and optimal treatment of CV risk factors and comorbidities are key strategies to reduce CV risk and improve survival in CKD. Beyond common CV risk factors, patients with CKD are often physically inactive and have low physical function leading to subsequent frailty with muscle fatigue and weakness, sarcopenia and increased risk of falling. Consequently, the economic health burden of CKD is high, requiring feasible strategies to counteract this vicious cycle. Regular physical activity and exercise training have been shown to be effective in improving risk factors, reducing CVD and reducing frailty and falls. Nonetheless, combining exercise training and a healthy lifestyle with pharmacological treatment is not frequently applied in clinical practice. For that reason, this Clinical Consensus Statement reviews the current literature and provides evidence-based data regarding the role of exercise training in reducing CV and overall burden in patients with CKD. The aim is to increase awareness among cardiologists, nephrologists, and health care professionals of the potential of exercise therapy in order to encourage implementation of exercise training in clinical practice, eventually reducing CV risk and disease, as well as reducing frailty in patients with CKD G3 to G5D.

An observational cohort study of histological screening for BK polyomavirus nephropathy following viral replication in plasma

Systematic screening for BKPyV-DNAemia has been advocated to aid prevention and treatment of polyomavirus associated nephropathy (PyVAN), an important cause of kidney graft failure. The added value of performing a biopsy at time of BKPyV-DNAemia, to distinguish presumptive PyVAN (negative SV40 immunohistochemistry) and proven PyVAN (positive SV40) has not been established. Therefore, we studied an unselected cohort of 950 transplantations, performed between 2008-2017. BKPyV-DNAemia was detected in 250 (26.3%) transplant recipients, and positive SV40 in 91 cases (9.6%). Among 209 patients with a concurrent biopsy at time of first BKPyV-DNAemia, 60 (28.7%) biopsies were SV40 positive. Plasma viral load showed high diagnostic value for concurrent SV40 positivity (ROC-AUC 0.950, 95% confidence interval 0.916-0.978) and the semiquantitatively scored percentage of tubules with evidence of polyomavirus replication (pvl score) (0.979, 0.968-0.988). SV40 positivity was highly unlikely when plasma viral load is below 4 log10 copies/ml (negative predictive value 0.989, 0.979-0.994). In SV40 positive patients, higher plasma BKPyV-DNA load and higher pvl scores were associated with slower viral clearance from the blood (hazard ratio 0.712, 95% confidence interval 0.604-0.839, and 0.327, 0.161-0.668, respectively), whereas the dichotomy positivity/negativity of SV40 immunohistochemistry did not predict viral clearance. Although the pvl score offers some prognostic value for viral clearance on top of plasma viral load, the latter provided good guidance for when a biopsy was unnecessary to exclude PyVAN. Thus, the distinction between presumptive and proven PyVAN, based on SV40 immunohistochemistry, has limited clinical value. Hence, management of BKPyV-DNAemia and immunosuppression reduction should be weighed against the risk of occurrence of rejection, or exacerbation of rejection observed concomitantly.

Transcriptional and spatial profiling of the kidney allograft unravels a central role for FcyRIII+ innate immune cells in rejection

Rejection remains the main cause of premature graft loss after kidney transplantation, despite the use of potent immunosuppression. This highlights the need to better understand the composition and the cell-to-cell interactions of the alloreactive inflammatory infiltrate. Here, we performed droplet-based single-cell RNA sequencing of 35,152 transcriptomes from 16 kidney transplant biopsies with varying phenotypes and severities of rejection and without rejection, and identified cell-type specific gene expression signatures for deconvolution of bulk tissue. A specific association was identified between recipient-derived FCGR3A+ monocytes, FCGR3A+ NK cells and the severity of intragraft inflammation. Activated FCGR3A+ monocytes overexpressed CD47 and LILR genes and increased paracrine signaling pathways promoting T cell infiltration. FCGR3A+ NK cells overexpressed FCRL3, suggesting that antibody-dependent cytotoxicity is a central mechanism of NK-cell mediated graft injury. Multiplexed immunofluorescence using 38 markers on 18 independent biopsy slides confirmed this role of FcγRIII+ NK and FcγRIII+ nonclassical monocytes in antibody-mediated rejection, with specificity to the glomerular area. These results highlight the central involvement of innate immune cells in the pathogenesis of allograft rejection and identify several potential therapeutic targets that might improve allograft longevity.

Monoclonal gammopathy of renal significance: Multidisciplinary approach to diagnosis and treatment

Monoclonal gammopathy of renal significance (MGRS) is a hemato-nephrological term referring to a heterogeneous group of kidney disorders characterized by direct or indirect kidney injury caused by a monoclonal immunoglobulin (MIg) produced by a B cell or plasma cell clone that does not meet current hematologic criteria for therapy. MGRS-associated kidney diseases are diverse and can result in the development of end stage kidney disease (ESKD). The diagnosis is typically made by nephrologists through a kidney biopsy. Many distinct pathologies have been identified and they are classified based on the site or composition of the deposited Mig, or according to histological and ultrastructural findings. Therapy is directed towards the identified underlying clonal population and treatment decisions should be coordinated between hematologists and nephrologists in a multidisciplinary fashion, depend on the type of MGRS, the degree of kidney function impairment and the risk of progression to ESKD.

Data-Driven Chronic Allograft Phenotypes: A Novel and Validated Complement for Histologic Assessment of Kidney Transplant Biopsies

BACKGROUND

No validated system currently exists to realistically characterize the chronic pathology of kidney transplants that represents the dynamic disease process and spectrum of disease severity. We sought to develop and validate a tool to describe chronicity and severity of renal allograft disease and integrate it with the evaluation of disease activity.

METHODS

The training cohort included 3549 kidney transplant biopsies from an observational cohort of 937 recipients. We reweighted the chronic histologic lesions according to their time-dependent association with graft failure, and performed consensus k-means clustering analysis. Total chronicity was calculated as the sum of the weighted chronic lesion scores, scaled to the unit interval.

RESULTS

We identified four chronic clusters associated with graft outcome, based on the proportion of ambiguous clustering. The two clusters with the worst survival outcome were determined by interstitial fibrosis and tubular atrophy (IFTA) and by transplant glomerulopathy. The chronic clusters partially overlapped with the existing Banff IFTA classification (adjusted Rand index, 0.35) and were distributed independently of the acute lesions. Total chronicity strongly associated with graft failure (hazard ratio [HR], 8.33; 95% confidence interval [CI], 5.94 to 10.88; P<0.001), independent of the total activity scores (HR, 5.01; 95% CI, 2.83 to 7.00; P<0.001). These results were validated on an external cohort of 4031 biopsies from 2054 kidney transplant recipients.

CONCLUSIONS

The evaluation of total chronicity provides information on kidney transplant pathology that complements the estimation of disease activity from acute lesion scores. Use of the data-driven algorithm used in this study, called RejectClass, may provide a holistic and quantitative assessment of kidney transplant injury phenotypes and severity.

Association of HLA Mismatches and Histology Suggestive of Antibody-Mediated Injury in the Absence of Donor-Specific Anti-HLA Antibodies

BACKGROUND AND OBJECTIVES

The histology of antibody-mediated rejection after kidney transplantation is observed frequently in the absence of detectable donor-specific anti-HLA antibodies. Although there is an active interest in the role of non-HLA antibodies in this phenotype, it remains unknown whether HLA mismatches play an antibody-independent role in this phenotype of microcirculation inflammation.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

To study this, we used the tools HLAMatchmaker, three-dimensional electrostatic mismatch score, HLA solvent accessible amino acid mismatches, and mismatched donor HLA-derived T cell epitope targets to determine the degree of HLA molecular mismatches in 893 kidney transplant recipients with available biopsy follow-up. Multivariable Cox proportional hazards models were applied to quantify the cause-specific hazard ratios of the different types of HLA mismatch scores for developing antibody-mediated rejection or histology of antibody-mediated rejection in the absence of donor-specific anti-HLA antibodies. In all survival analyses, the patients were censored at the time of the last biopsy.

RESULTS

In total, 121 (14%) patients developed histology of antibody-mediated rejection in the absence of donor-specific anti-HLA antibodies, of which 44 (36%) patients had concomitant T cell-mediated rejection. In multivariable Cox analysis, all different calculations of the degree of HLA mismatch associated with developing histology of antibody-mediated rejection in the absence of donor-specific anti-HLA antibodies. This association was dependent neither on the presence of missing self (potentially related to natural killer cell activation) nor on the formation of de novo HLA antibodies. Also, glomerulitis and complement C4d deposition in peritubular capillaries associated with the degree of HLA mismatch in the absence of anti-HLA antibodies.

CONCLUSIONS

The histology of antibody-mediated rejection and its defining lesions are also observed in patients without circulating anti-HLA antibodies and relate to the degree of HLA mismatch.

MO590: A Home-Based Exercise and Physical Activity Intervention After Kidney Transplantation: Impact of Exercise Intensity. The Phoenix-Kidney Study Protocol

BACKGROUND AND AIMS

Advances in the field of kidney transplantation have led to improved postoperative survival rates, but age-standardized mortality nonetheless remains 2- to 7-fold higher in kidney transplant recipients—with cardiovascular disease representing the leading cause of death in recipients with a functioning graft. Poor physical fitness, not completely recovering after transplantation, adds to the heightened cardiovascular risk of hypertension, diabetes, dyslipidemia and obesity. So does the post-transplant continuation of gut microbial dysbiosis, which recently emerged as a modulator of muscular, metabolic and cardiovascular health. Exercise-based rehabilitation and physical activity interventions may prove pivotal in the care of kidney transplant recipients to address aforementioned outcomes.

METHOD

At 3 months post-transplant, a probability sample of 147 adult kidney transplant recipients from two independent Belgian transplant centers will be randomly allocated to either 6 months of home-based moderate-intensity training (MIT, n = 49), concurrent moderate- and high-intensity training (MHIT, n = 49) or usual care (CON, n = 49) (Figure1). High-intensity training sessions in MHIT are based on the Scandinavian model (four blocks of 4 min at high intensity interspersed by 3 min of active recovery), performed twice a week, and of equivalent energy expenditure as moderate-intensity training (Figure2). MIT and MHIT will perform similar muscle strengthening exercises, twice a week. The training intervention will be followed by an individualized activity intervention aiming for long-term physical activity maintenance in MIT and MHIT; using motivational interviewing techniques, co-creation of an action plan adapted to the patients’ preferences, goal-setting, gradually decreasing follow-up prompts over time and self-monitoring of physical activity behavior. Study participants will be followed-up till 2 years after transplantation. We hypothesize that the study intervention will improve our primary outcome cardiorespiratory fitness, assessed as peak oxygen uptake, at 9 months post-transplant. Secondary outcomes include muscle fitness, motor fitness, body composition, cardiovascular health, gut microbiome characteristics, health-related quality of life, safety, cost-effectiveness and implementation outcomes (Figure1). The role of training intensity and the role of baseline gut microbiome characteristics as predictor of individuals’ training response will be explored.

RESULTS

Results from this two-phased RCT will provide novel insights in the safety, implementation potential, cost-effectiveness and effectiveness of a home-based exercise program and physical activity intervention in de novo kidney transplant recipients to improve physical fitness, cardiovascular health, gut microbiome characteristics and health-related quality of life.

CONCLUSION

PHOENIX-kidney represents the first adequately powered multicenter RCT evaluating basic, clinical and health-economic outcome parameters in response to an exercise training and physical activity intervention in kidney transplant recipients.

MO917: Self-Reported Perceptions of Haemodialysis Patients´ Cognitive State––The Goodrenal Project

BACKGROUND AND AIMS

Patients with chronic kidney disease have an increased risk of developing cognitive impairment and neurocognitive disorders including Alzheimer's disease that affect their quality of life. Changes involve deterioration of domains such as learning and memory, language, attention, executive function, perceptual motor or social cognition. We explored the subjective perception that the patients have regarding their cognitive state.

METHOD

This study is part of the GoodRENAL project, which is funded by the European Community Erasmus + and involves four countries: Belgium, Greece, Spain and Sweden. Exploratory questionnaires regarding patients’ cognitive state were answered by 38 patients (mean age 58 ± 0.5 years; 50% women) randomly allocated to this study from the dialysis shifts. The questionnaire had 10 questions with answers rated as 1 (never), 2 (sometimes), 3 (half of the time), 4 (more than half of the time) and 5 (almost all the time), plus 1 open question about main barriers, difficulties or needs related to their cognitive state.

RESULTS

To analyse the descriptive data, the response frequency was grouped into items based on the frequency of the occurrence (almost all the time and all the time). The table below summarizes answers received from patients.

CONCLUSION

The patients’ perception of their attention capacity, memory function and learning capacity was in general positive. However, further studies using validated questionnaires regarding different aspects such as attention, memory or learning functionality are needed to confirm these findings.

FC 117: Clinical Validation of Automated Urinary Chemokine Assays for Non-Invasive Detection of Kidney Transplant Rejection: A Large Prospective Cohort Study

BACKGROUND AND AIMS

The urinary chemokines CXCL9 and CXCL10 have been extensively studied as biomarkers for kidney transplant rejection. However, final validation in a sufficiently large, real-world prospective cohort is needed to determine the relation to rejection subtypes and clinical confounders, the context of use and the added benefit for clinical practice.

METHOD

In this single-centre prospective cohort study, we analysed 1559 biopsy-paired urine samples at both indication and protocol time points from 622 kidney transplants performed between April 2013 and July 2019. We quantified urinary CXCL9 and CXCL10 using automated immunoassays and normalized the values to urinary creatinine. In addition to evaluating diagnostic performance for Banff-grade rejection, we also considered rejection as assessed by the molecular microscope.

RESULTS

The urinary chemokines strongly associated with the inflammation severity in the biopsy, when considering classical semi-quantitative histological scores, but also when considering molecular rejection scores. The diagnostic performance of urinary chemokines alone was moderate for Banff acute rejection, and increased when considering treated rejection or molecular rejection instead (Figure 1). Taking into account confounding factors rather than excluding them, an integrated model of urinary chemokines with eGFR, donor-specific antibodies, time post-transplant and polyoma viremia had a high diagnostic value for acute rejection (N = 150) [ROCAUC 82.6%, 95% confidence interval (95% CI) 78.9–86.2] and added value on top of clinical standard-of-care. The integrated score would help to safely avoid 59 protocol biopsies per 100 patients when the predicted rejection risk is less than 10%.

CONCLUSION

The integration of urinary chemokines and clinical markers allows for personalized noninvasive monitoring of rejection probability and enables to importantly and safely reduce the number of unnecessary biopsies. We expect this study to pave the way for the final implementation of urinary chemokine measurements as noninvasive markers of rejection in routine clinical follow-up after kidney transplantation.

MO925: Psychological Wellbeing in Haemodialysis Patients: Comparing Perspectives From Patients, Caregivers and Healthcare Professionals––The Goodrenal Project

BACKGROUND AND AIMS

The start of dialysis therapy can contribute to the development of depression, stress and anxiety, which, in turn, has an impact on the patient´s quality of life, the disease process and the associated social and health care costs. This underlines the importance of studies that analyse the psychological profiles of patients on maintenance dialysis to establish relationships between risk factors, prevention steps and intervention strategies aimed at improving their quality of life. Therefore, we explored the perceptions regarding the patient's psychological wellbeing, seen from three different perspectives: patients’ own, their caregivers’ and that of their healthcare professionals (HCPs).

METHOD

This study is part of the GoodRENAL Project, which is funded by the European Community Erasmus + and involves four countries: Belgium, Greece, Spain and Sweden. Exploratory questionnaires regarding patients’ psychological wellbeing were developed by the team, and responses were obtained from three groups of stakeholders: 38 patients, who were randomly allocated to this study from the first dialysis shift of the week (mean age 58 ± 0.51 years; 50% women); 34 caregivers (mean age 54 ± 13 years; 80% women); and 39 healthcare professionals (HCPs mean age 42 ± 10 years; 79% women).

The exploratory questionnaires comprised different parts, exploring the psychological state of patients through closed questions, open questions and questions about barriers, needs and facilitators regarding psychological wellbeing. The patients’ and caregivers’ questionnaires had 10 items scored from 1 (‘never’) to 5 (‘almost all the time’). The HCPs questionnaire included 10 items rated as 1 (‘totally disagree’) to 5 (‘totally agree’).

RESULTS

To analyse the descriptive data, the response frequency was grouped into items based on the level of agreement or the frequency of the occurrence (almost all the time and all the time). The table below shows answers received from patients, caregivers and HCPs.

CONCLUSION

Patients consistently reported a much more positive subjective perception of their psychological state, compared with that assumed by HCPs, while the perceived perception of patients’ states reported by their caregivers was in general closer to that reported by the patients. The extent by which patients’ positive responses are related to adaptations such as social desirability, distorted subjective perception, minimization or normalization of symptomatology should be explored in further studies.

MO560: Adherence to Nutritional Recommendations as Expressed by Patients on Hemodialysis, Their Informal Carers and Healthcare Professionals—the Goodrenal Project

BACKGROUND AND AIMS

Low adherence to nutritional recommendations is common in patients on hemodialysis (HD), but the reasons are not well known. We explored the main needs, barriers and facilitators affecting nutritional adherence as experienced by patients on HD, their informal carers and their healthcare professionals (HCPs) at the dialysis centre.  

METHOD

This study is part of the GoodRENal project—funded by the European Community, Erasmus + program that comprises four countries: Spain, Sweden, Belgium and Greece. As part of this project, exploratory questionnaires were constructed and answered by the patients, their carers and their HCPs. The questionnaire comprised three sections consisting of statements exploring the needs, barriers and facilitators affecting adherence to nutritional recommendations for patients on HD. Each statement could be rated from 1 (strongly disagree), 2 (disagree), 3 (neither agree or disagree), 4 (agree) to 5 (strongly agree). In addition, there was a section for free text. To avoid bias in patient selection, 10 patients were randomized from the first dialysis shift of the week in the four participating countries. 

RESULTS

In total, 40 patients, 40 informal carers and 40 HCPs HealthCP accepted to participate, out of whom 38 patients (68% male, 62 ± 15 years), 33 informal carers (21% male, age 54 ± 12 years, of whom 68% were spouses) and 37 HCPs (22% male, age 42 ± 10 years, 60% were nurses) answered the questionnaires. Two of the four centres had a dedicated dietitian at the dialysis unit, who worked there on average 18 ± 8 hours per week. At the dialysis units without a dietitian, the nurses and doctors were responsible for nutritional care. To simplify the analysis, answers rated as 4 and 5 were grouped as agree. The main findings are presented below:

CONCLUSION

These descriptive findings show that patients, informal carers and HCPs identified different needs, barriers, and facilitators to increase adherence to nutritional recommendations. These results can be used to build and tailor strategies aimed at patients, informal carers and HCPs.

MO619GOODRENAL: HOLISTIC PATIENT CARE INTRADIALYSIS PROGRAM IN HEMODIALYSIS THROUGH A VIRTUAL HEALTH PLATFORM

Background and Aims

There is wide evidence that weak points of the care of end-stage Chronic kidney disease (CKD) patients in hemodialysis include three aspects that are suitable for intervention: exercise, nutrition and psychological support. Evidence shows that exercise for patients on hemodialysis results in increased functional capacity and strength and improved health-related quality of life and survival. Additionally, earlier studies have shown the benefits of psychological interventions and the positive effect of educational programs on nutritional status for patients on hemodialysis. Despite the well-known benefits of exercise, these programs are not being implemented in the routine clinical care of hemodialysis patients. Thus, the GoodRENal project aims to promote a healthy lifestyle among hemodialysis patients using a holistic pedagogical approach that, addressing adult learners, combines exercise, nutrition and psychological well-being as well as cognitive functioning.

Method

GoodRENal is a project funded by the European Community, Erasmus + program (336.327 euros). The project will last 3 years, from September 2020 to August 2023 and the Partners of the consortium include institutions from five European countries: Spain (Universidad CEU Cardenal Herrera, Hospital de Manises, Univesitat de Valéncia, Universitat Politécnica de Valéncia), Sweden (Skane University Hospital and Karolinska Institutet), Greece (Aristotles University of Thessaloniki) and Belgium (Katholieke Universiteit Leuven). Other supporting institutions are located in the UK, Chile and Brazil.

Results

The project will develop a virtual platform comprising three aspects of care: physical activity/exercise, nutrition, psychological well-being/cognition. In summary, the project outputs will be: 1. A didactic content on a modular platform with an educational program for integrated treatment in patients on hemodialysis; 2. A guideline to promote a healthy lifestyle among patients on hemodialysis for healthcare providers; 3. A guideline to promote a healthy lifestyle among patients on hemodialysis for patients, and their formal- and non-formal carers. At the present stage exploratory questionnaires regarding physical activity/exercise-nutrition-psychological well-being/cognition have been developed in consensus with all the partners. Data from this first exploratory study regarding needs and barriers of the stakeholders (patients, health professionals, carers) will be presented at the ERA-EDTA congress.

Conclusion

GoodRENal aims at improving the overall health, and thus the health-related quality of life, of patients on hemodialysis through a holistic and pedagogical approach that will target especially improvements of patient reported outcomes including quality of life.

Data-driven Derivation and Validation of Novel Phenotypes for Acute Kidney Transplant Rejection using Semi-supervised Clustering

BACKGROUND

Over the past decades, an international group of experts iteratively developed a consensus classification of kidney transplant rejection phenotypes, known as the Banff classification. Data-driven clustering of kidney transplant histologic data could simplify the complex and discretionary rules of the Banff classification, while improving the association with graft failure.

METHODS

The data consisted of a training set of 3510 kidney-transplant biopsies from an observational cohort of 936 recipients. Independent validation of the results was performed on an external set of 3835 biopsies from 1989 patients. On the basis of acute histologic lesion scores and the presence of donor-specific HLA antibodies, stable clustering was achieved on the basis of a consensus of 400 different clustering partitions. Additional information on kidney-transplant failure was introduced with a weighted Euclidean distance.

RESULTS

Based on the proportion of ambiguous clustering, six clinically meaningful cluster phenotypes were identified. There was significant overlap with the existing Banff classification (adjusted rand index, 0.48). However, the data-driven approach eliminated intermediate and mixed phenotypes and created acute rejection clusters that are each significantly associated with graft failure. Finally, a novel visualization tool presents disease phenotypes and severity in a continuous manner, as a complement to the discrete clusters.

CONCLUSIONS

A semisupervised clustering approach for the identification of clinically meaningful novel phenotypes of kidney transplant rejection has been developed and validated. The approach has the potential to offer a more quantitative evaluation of rejection subtypes and severity, especially in situations in which the current histologic categorization is ambiguous.

Strategies for asymmetrical triacetate dialyser heparin-free effective haemodialysis: the SAFE study

Background

In haemodialysis, maintaining patency of the extracorporeal circuit requires the use of anticoagulants. Although (low molecular weight) heparins are the mainstay, these are not well tolerated in all patients. Alternative approaches include saline infusion, citrate-containing dialysate, regional citrate anticoagulation or the use of heparin-coated membranes. Asymmetric cellulose triacetate (ATA) dialysers have a low degree of platelet contact activation and might be an alternative to heparin-coated dialysers. The aim of this study was to test the clotting propensity of ATA when used without systemic anticoagulation.

Methods

We performed a Phase II pilot study in maintenance dialysis patients. The ‘Strategies for Asymmetrical Triacetate dialyzer heparin-Free Effective hemodialysis’ (SAFE) study was a two-arm open-label crossover study. In Arm A, patients were dialysed using 1.9 m² ATA membranes in combination with a citrate-containing dialysate (1 mM). In Arm B, the ATA membrane was combined with high-volume predilution haemodiafiltration (HDF) without any other anticoagulation. The primary endpoint was the success rate to complete 4 h of haemodialysis without preterm clotting. Secondary endpoints included time to clotting and measures of dialysis adequacy.

Results

We scheduled 240 dialysis sessions (120/arm) in 20 patients. Patients were randomized 1:1 to start with Arm A or B. All patients crossed to the other arm halfway through the study. A total of 232 (96.7%) study treatments were delivered. Overall, 23 clotting events occurred, 7 in Arm A and 16 in Arm B. The success rate in Arm A (ATA + citrate-containing dialysate) was 90.8/94.0% [intention to treat (ITT)/as treated]. The success rate in Arm B (ATA + predilution HDF) was 83.3/86.2% (ITT/as treated). Time to clotting was borderline significantly better in Arm A (Mantel-Cox log rank P = 0.05).

Conclusion

ATA dialysers have a low clotting propensity and both predilution HDF and a citrate-containing dialysate resulted in high rates of completed dialysis sessions.

P1611PRE-ANALYTICAL CONSIDERATIONS IN STUDYING CIRCULATING MICRORNA EXPRESSION: COMPARISON BETWEEN PAIRED EDTA PLASMA, EDTA WHOLE BLOOD AND PAXGENE BLOOD RNA TUBES

Background and Aims

microRNA (miRNA) dysregulations have been related to pathological processes, including kidney disease. Relative stability in blood makes miRNAs attractive biomarkers. The current recommendation is to use fresh EDTA plasma samples (i.e. processed within 30 min. from sampling) to study circulating miRNA. However, cumbersome logistics might preclude broad implementation. Therefore, we investigated the potential of whole blood EDTA and PAXgene blood RNA tubes as alternative sources to study circulating microRNA expression profiling.

Method

Paired EDTA plasma, EDTA whole blood and PAXgene blood RNA tubes were obtained from 10 healthy adults (50% male). EDTA plasma samples were processed within 30 min. after sampling and immediately stored at -80°C. EDTA whole blood tubes and PAXgene tubes were kept at room temperature for 48 hours after sampling. Subsequently, the content of the EDTA whole blood samples was transferred to a 15 mL Falcon tube and stored at -80°C. PAXgene tubes were transferred to -20°C following the manufacturer’s protocol. Within 1 month of storage, all samples were thawed and miRNA was extracted using the Qiagen miRNeasy serum/plasma kit and subjected to RNA-sequencing (Oxford Genomics Centre). Based on the raw data, a count table was created using the online tool miRDeep* for the identification of both novel and known microRNAs. Subsequent downstream bio-informatic analyses approaches consisted of 1) unsupervised hierarchical clustering with principal component analysis (PCA); 2) calculation of differential miRNA expression using generalized linear models with differences considered significant if the false discovery rate-adjusted p-value was inferior to 10%.

Results

Initial assessment of the count table showed significant differences in the number of detected microRNAs. A median of 220 different microRNAs was detected in EDTA plasma samples versus 661 in PaxGene samples (p &lt; 0.05) and 490 in EDTA whole blood samples (p &lt; 0.05) (Figure 1A). We also found fewer novel miRNAs in EDTA plasma samples than in PAXgene samples (p &lt; 0.001) and EDTA whole blood samples (p &lt; 0.05). Low count microRNAs, defined as below 10 reads in more than 20% of the samples, were more abundant in Paxgene samples versus EDTA plasma samples (p = 0.0039), but this difference was not significant when comparing EDTA whole blood samples with EDTA plasma samples (Figure 1B). PCA analysis (Figure 1C) showed a clear separation of samples according to the blood collection method, strongly suggesting that the blood collection method predominantly determines the miRNA expression profile.

Conclusion

Bio-informatic analyses demonstrated different miRNA expression profiles according to three different blood collection methods, underpinning the importance of a standardized method for the collection of blood aimed at studying circulating miRNAs. As such, this study has important implications for the design of novel studies aiming to investigate circulating miRNAs.

TO011HEALTH UTILITY BUT NOT UREMIC TOXINS ARE ASSOCIATED WITH ONE YEAR MORTALITY IN HD PATIENTS

Background and Aims

Patient centred care is progressively gaining importance. Standardized outcomes should take into account patient relevant outcomes, such as mortality and quality of life. It is unknown whether the health utility index EQ5D, an objective assessment of quality of life, is associated with mortality in haemodialysis patients. Serum concentrations of different uremic toxins have been associated with survival. We intended to explore whether EQ5D rather than concentrations of representative uraemic toxins (UT) was associated with mortality.

Method

Prospective longitudinal multicentric cohort study of all haemodialysis patients at 5 representative dialysis centres in Flanders. Total and free concentrations of representative uraemic toxins indoxyl sulfate (IxS), p-cresyl sulfate (pCS), p-cresyl glucuronide (pCG), indole acetic acid (IAA), 3-carboxy-4-methyl-5-propyl-2-furanpropionic acid (CMPF), hippuric acid (HA) and uric acid (UA) were determined at baseline. Mini Nutritional Assessment (MNA) and EQ5D were assessed by dedicated nurses. Mortality was assessed from administrative or medical records. A Cox regression model was built, both fixed and as conditional forward including clinical parameters, MNA, EQ5D and serum concentrations of the different uraemic toxins.

Results

216 prevalent patients (62%male, age 67.2 ± 15.7) all on high flux haemodialysis were included. Over the observation period, 59 patients (27%) died. Health utility as assessed by EQ5D was 0.69±0.28; perceived health by visual analogue scale (VAS) (0-100) was 59.6±18.6. Adjusting for age, gender and MNA score, free but not total concentrations of IxS, pCS and IAA and EQ5D score were associated with overall survival in the forced entry model. However, neither in the fixed entry, the forward or backward model were serum concentrations of uraemic toxins retained, and only age, gender, BMI, EQ5D and VAS were consistently associated with survival.

Conclusion

Measures of health utility, such as EQ5D, and quality of life, such as a simple VAS score, are more predictive of survival in patients on regular haemodialysis than serum concentrations of a panel of relevant uraemic toxins. Health utility and QoL are thus not only directly relevant to patients, but also indirectly through an association with improved survival.

The concept of dialysis adequacy has been challenged over the last decade, mainly because it was focusing on small solute clearance. Different authors reported that concentrations of middle molecular and protein bound solutes were more representative. In our study, free but not total solute concentrations were associated with survival. However, adjusting additionally for health utility and/or health perception and/or assessment of nutritional status abolishes this association. Studies assessing interventions to enhance solute removal should not only include solute concentrations as outcome, but also consider EQ5D, VAS and nutritional status as important outcomes to enhance patient centeredness of their findings.

P1064HEPARIN-FREE DIALYSIS: A PHASE II PILOT STUDY USING ASYMMETRIC TRIACETATE (ATA) CELLULOSE DIALYZERS

Background and Aims

Not all dialysis patients tolerate heparin anticoagulation. Heparin should be avoided in patients at high risk of bleeding. Strategies include saline infusion, citrate-containing dialysate, regional citrate anticoagulation and heparin-coated membranes. We recently studied the combination of a heparin-coated membrane and citrate-containing dialysate, with a success rate of 94% . Although this combination resulted in low rates of clotting, heparin-coated membranes are not ubiquitously available. The quest for easy to perform, safe and affordable heparin-free dialysis is on. Asymmetric cellulose triacetate (ATA) dialyzers have a low degree of platelet contact activation and might be an alternative to heparin-coated dialyzers.

Method

We performed a phase II pilot study in maintenance dialysis patients. The ‘Strategies for Asymmetrical Triacetate dialyzer heparin-Free Effective hemodialysis (SAFE study)’ was a two-arm open-label cross-over study. In Arm 1, patients were dialyzed using a 1.9 m2 ATA membrane (Solacea™-19H, Nipro Corp., Japan) in combination with citrate (1 mM) containing dialysate. In Arm 2, patients were dialyzed with the same 1.9 m2 ATA membrane, in combination with high volume predilution hemodiafiltration. The primary endpoint was the success rate to complete 4 hours of hemodialysis without preterm clotting.

Results

We scheduled 240 dialysis sessions (120 per arm) in twenty patients. Ten patients were randomized to start in Arm 1, the others to Arm 2. All patients crossed to the other arm halfway the study. 232 (96.7%) study treatments were delivered. Overall, 23 clotting events occurred, 7 in Arm 1 and 16 in Arm 2. Success rate in Arm 1 (ATA + citrate containing dialysate) was 90.8 / 94.0 % (intention to treat/ as treated). Success rate in Arm 2 (ATA + predilution HDF) was 83.3 / 86.2 % (intention to treat/ as treated). Therapy survival was borderline significantly better in Arm 1(Mantel-Cox log rank P = 0.05).

Conclusion

Asymmetric cellulose triacetate (ATA) dialyzers have a low clotting propensity. In combination with citrate-containing dialysate, asymmetric cellulose triacetate (ATA) may be a suitable alternative to heparin-coated membranes for systemic heparin-free hemodialysis.