Cardiovascular Risk in Patients With Glomerular Disease: A Narrative Review of the Epidemiology, Mechanisms, Management, and Patient Priorities

Purpose of review

Cardiovascular (CV) disease is a major cause of morbidity and mortality for patients with glomerular disease. Despite the fact that mechanisms underpinning CV disease risk in this population are likely distinct from other forms of kidney disease, treatment and preventive strategies tend to be extrapolated from studies of patients with undifferentiated chronic kidney disease (CKD). There is an unmet need to delineate the pathophysiology of CV disease in patients with glomerular disease, establish unique risk factors, and identify novel therapeutic targets for disease prevention. The aims of this narrative review are to summarize the existing knowledge regarding the epidemiology, molecular mechanisms, and management of CV disease in patients with common glomerular disease, highlight the patient perspective, and propose specific areas for future study.

Sources of information

The literature for this narrative review was accessed using common research search engines, including PubMed, PubMed Central, Medline, and Google Scholar. Information for the patient perspective section was collected through iterative discussions with a patient partner.

Methods

We reviewed the epidemiology, molecular mechanisms of disease, management approaches, and the patient perspective in relation to CV disease in patients with glomerulopathies. Throughout, we have highlighted the current knowledge and have discussed future research approaches, both clinical and translational, while integrating the patient perspective.

Key findings

Patients with glomerular disease have significant CV disease risk driven by multifactorial, molecular mechanisms originating from their glomerular disease but complicated by existing comorbidities, kidney disease, and medication side effects. The current approach to risk stratification and treatment relies heavily on existing data from CKD patients, but this may not always be appropriate given the unique pathophysiology and mechanisms associated with CV disease risk in patients with glomerular disease. We highlight the need for ongoing glomerular disease-focused studies aimed to better delineate CV disease risk, while integrating the patient perspective.

Limitations

This is a narrative review and does not represent a comprehensive and systematic review of the literature.

Assessing Discharge Communication and Follow-up of Acute Kidney Injury in British Columbia: A Retrospective Chart Review

Background and objective

Acute kidney injury (AKI) affects up to 20% of hospitalizations and is associated with chronic kidney disease, cardiovascular disease, increased mortality, and increased health care costs. Proper documentation of AKI in discharge summaries is critical for optimal monitoring and treatment of these patients once discharged. Currently, there is limited literature evaluating the quality of discharge communication after AKI. This study aimed to evaluate the accuracy and quality of documentation of episodes of AKI at a tertiary care center in British Columbia, Canada.

Methods design setting patients and measurements

This was a retrospective chart review study of adult patients who experienced AKI during hospital admission between January 1, 2018, and December 31, 2018. Laboratory data were used to identify all admissions to the cardiac and general medicine ward complicated by AKI defined by the Kidney Disease Improving Global Outcomes (KDIGO) criteria. A random sample of 300 AKI admissions stratified by AKI severity (eg, stages 1, 2, and 3) were identified for chart review. Patients were excluded if they required ongoing renal replacement therapy after admission, had a history of kidney transplant, died during their admission, or did not have a discharge summary available. Discharge summaries were reviewed for documentation of the following: presence of AKI, severity of AKI, AKI status at discharge, practitioner and laboratory follow-up plans, and medication changes.

Results

A total of 1076 patients with 1237 AKI admissions were identified. Of the 300 patients selected for discharge summary review, 38 met exclusion criteria. In addition, AKI was documented in 140 (53%) discharge summaries and was more likely to be documented in more severe AKI: stage 1, 38%; stage 2, 51%; and stage 3, 75%. Of those with their AKI documented, 94 (67%) documented AKI severity, and 116 (83%) mentioned the AKI status or trajectory at the time of discharge. A total of 239 (91%) of discharge summaries mentioned a follow-up plan with a practitioner, but only 23 (10%) had documented follow-up with nephrology. Patients with their AKI documented were more likely to have nephrology follow-up than those without AKI documented (17% vs 1%). Regarding laboratory investigations, 92 (35%) of the summaries had documented recommendations. In summaries that included medications typically held during AKI, only about half made specific reference to those medications being held, adjusted, or documented a post-discharge plan for that medication. For those with nonsteroidal anti-inflammatory drugs (NSAIDs) listing, 64% of discharge summaries mentioned holding, and 9% mentioned a discharge plan. For those with angiotensin converting enzyme inhibitor (ACEi)/angiotensin II receptor blocker (ARB) listing, 38% mentioned holding these medications, and 46% mentioned a discharge plan. In summaries with diuretics listed, 35% mentioned holding, and 51% included a discharge plan.

Conclusions and limitations

We found suboptimal quality and completeness of discharge reporting in patients hospitalized with AKI. This may contribute to inadequate follow-up and post-hospitalization care for this patient population. Strategies are required for increasing the presence and quality of AKI reporting in discharge summaries. Limitations include our definition of AKI based on lab criteria, which may have missed some of the injuries that met the criteria based on urine output. Another limitation is that our definition of AKI based on the highest and lowest creatinine during admission may have led to some overclassification. In addition, without outpatient laboratories, it is possible that we have not captured the true baseline creatinine in some patients.

The Association Between Serum Vancomycin Level and Clinical Outcome in Patients With Peritoneal Dialysis Associated Peritonitis

Introduction

Intraperitoneal (IP) vancomycin is often first-line empiric therapy and then maintenance therapy for peritoneal dialysis (PD) peritonitis. However, how vancomycin serum levels correlate with clinical outcomes remains unclear.

Methods

We conducted a retrospective single-center adult cohort study of 98 patients with PD peritonitis treated with IP vancomycin between January 2016 and May 2022. The association between nadir vancomycin level and cure was evaluated in a logistic regression model, first unadjusted and then adjusted for age, sex, weight, glomerular filtration rate (GFR), and total number of days on PD. Vancomycin was assessed both as a continuous exposure (per 1 mg/l increase) and as a categorical exposure (<15 mg/l vs. ≥15 mg/l). A receiver operating characteristic curve (ROC) was created to explore nadir vancomycin level thresholds in an attempt to identify an optimal target level during treatment.

Results

Of the patients, 81% achieved cure, and patients with nadir vancomycin level ≥15 mg/l were 7.5 times more likely to experience cure compared to those with a nadir level <15 mg/l (odds ratio [OR] 7.58, 95% confidence interval [CI] 1.71-33.57, P = 0.008). Weight, GFR, days on PD, sex, and age were not independently associated with outcome. The vancomycin level with the greatest discriminatory capacity for cure on the ROC analysis was 14.4 mg/l.

Conclusion

Increasing IP vancomycin serum levels are associated with increased odds of cure; and maintaining vancomycin serum levels above 14-15 mg/l throughout the course of PD peritonitis treatment is likely to improve clinical outcomes.

Incidence of and Risk Factors for Active Tuberculosis Disease in Individuals With Glomerular Disease: A Canadian Cohort Study

RATIONALE & OBJECTIVE

Kidney failure is an established risk factor for active tuberculosis (TB) but the risk of TB has not been reported in specific kidney diseases. We sought to determine the incidence of and risk factors for active TB in patients with glomerular disease.

STUDY DESIGN

Observational cohort study.

SETTING & PARTICIPANTS

A provincial kidney pathology registry (2000-2012) was used to identify 3,079 adult patients with IgA nephropathy, focal segmental glomerulosclerosis (FSGS), antineutrophil cytoplasmic antibody (ANCA)-related glomerulonephritis, lupus nephritis, membranous nephropathy, minimal change disease, or "other" glomerular diseases in British Columbia, Canada.

EXPOSURE

Predictors included demographics, immigration status, comorbidities, immunosuppression use, estimated glomerular filtration rate (eGFR), and proteinuria.

OUTCOME

A diagnosis of active TB was ascertained using administrative data linkages and defined based on (1) the dispensation of 1 or more unique combinations of medications used to treat active TB, or (2) physician or hospital visits for active TB.

ANALYTICAL APPROACH

The definition of TB was validated in an external cohort linked to the Provincial TB registry at the BC Centre for Disease Control (BCCDC). Standardized incidence ratios were calculated using the age-matched general population. Risk factors for active TB were identified using Cox proportional hazards regression analysis.

RESULTS

The sensitivity and specificity of the outcome definition of active TB were 87.6% and 99.5%, respectively. During a median follow-up of 6.2 years, 41 patients developed active TB with an incidence of 197 of 100,000 person-years, approximately 23 times as high as the general population and>6 times higher than the threshold of 30 per 100,000 used to define high TB incidence. A high incidence was observed in all glomerular diseases (range, 110-403 per 100,000), in both Canadian- and foreign-born patients (range, 124-424 per 100,000), and in patients exposed or not to immunosuppression (282 vs 147 per 100,000). Factors associated with higher TB risk included immigration from a high-incidence country (HR, 3.90 [95% CI, 1.75-8.68]), diminished eGFR (HR, 2.81 [95% CI, 1.18-6.69]), higher levels of proteinuria (HR, 1.15 [95% CI, 1.04-1.27]), lupus nephritis (HR, 2.79 [95% CI, 1.37-5.68]), and immunosuppression use (HR, 2.13 [95% CI, 1.13-4.03]).

LIMITATIONS

A relatively low number of events contributed to uncertainty in risk estimates.

CONCLUSIONS

Patients with glomerular disease have a high incidence of active TB irrespective of disease type, demographics, or use of immunosuppression. Prospective studies are needed to evaluate the utility of screening for latent TB infection in this population.

PLAIN-LANGUAGE SUMMARY

Patients with kidney failure are at high risk of developing tuberculosis (TB), a major infection that can be prevented by identifying and treating patients who have had prior exposure to TB. The risk of TB in specific kidney diseases is unknown. In this Canadian study of 3,079 patients with glomerular disease, a group of autoimmune kidney conditions, the rate of TB was 23 times higher than in the general population. The rate was high irrespective of the use of immunosuppressive drugs or whether patients had immigrated to Canada from another country. These findings suggest that screening patients with glomerular disease for prior TB exposure may be beneficial; however, this needs to be evaluated in a prospective study.

Stroke Subtype Among Individuals With Chronic Kidney Disease

Background

It is widely accepted that there is a stepwise increase in the risk of acute ischemic stroke with chronic kidney disease (CKD). However, whether the risk of specific ischemic stroke subtypes varies with CKD remains unclear.

Objective

To assess the association between ischemic stroke subtypes (cardioembolic, arterial, lacunar, and other) classified using the Trial of ORG 10172 in Acute Stroke Treatment (TOAST) and CKD stage.

Design

retrospective cohort study.

Setting

Ontario, Canada.

Patients

A total of 17 434 adults with an acute ischemic stroke in Ontario, Canada between April 1, 2002 and March 31, 2013, with an estimated glomerular filtration rate (eGFR) measurement or receipt of maintenance dialysis captured in a stroke registry were included.

Measurements

Kidney function categorized as an eGFR of ≥60, 30-59, <30 mL/min/1.73 m2, or maintenance dialysis. Ischemic stroke classified by TOAST included arterial, cardioembolic, lacunar, and other (dissection, prothrombotic state, cortical vein/sinus thrombosis, and vasculitis) types of strokes.

Methods

Adjusted regression models.

Results

In our cohort, 58.9% had an eGFR of ≥60, 34.7% an eGFR of 30-59, 6.0% an eGFR of <30 and 0.5% were on maintenance dialysis (mean age of 73 years; 48% women). Cardioembolic stroke was more common in patients with non-dialysis-dependant CKD (eGFR 30-59: 50.4%, adjusted odds ratio [OR] 1.20, 95% confidence interval [CI]: 1.02, 1.44; eGFR<30: 50.6%, OR 1.21, 95% CI: 1.02, 1.44), whereas lacunar stroke was less common (eGFR 30-59: 22.7% OR 0.85, 95% CI: 0.77, 0.93; eGFR <30: 0.73, 95% CI: 0.61, 0.88) compared with those with an eGFR ≥60. In stratified analyses by age and CKD, lacunar strokes were more frequent in those aged less than 65 years, whereas cardioembolic was higher in those aged 65 years and above.

Limitations

TOAST classification was not captured for all patients.

Conclusion

Non-dialysis CKD was associated with a higher risk of cardioembolic stroke, whereas an eGFR ≥60 mL/min/1.73 m2 was associated with a higher risk of lacunar stroke. Detailed stroke subtyping in CKD may therefore provide mechanistic insights and refocus treatment strategies in this high-risk population.

Regional Variation in Hemoglobin Distribution Among Individuals With CKD: the ISN International Network of CKD Cohorts

Introduction

Despite recognized geographic and sex-based differences in hemoglobin in the general population, these factors are typically ignored in patients with chronic kidney disease (CKD) in whom a single therapeutic range for hemoglobin is recommended. We sought to compare the distribution of hemoglobin across international nondialysis CKD populations and evaluate predictors of hemoglobin.

Methods

In this cross-sectional study, hemoglobin distribution was evaluated in each cohort overall and stratified by sex and estimated glomerular filtration rate (eGFR). Relationships between candidate predictors and hemoglobin were assessed from linear regression models in each cohort. Estimates were subsequently pooled in a random effects model.

Results

A total of 58,613 participants from 21 adult cohorts (median eGFR range of 17-49 ml/min) and 3 pediatric cohorts (median eGFR range of 26-45 ml/min) were included with broad geographic representation. Hemoglobin values varied substantially among the cohorts, overall and within eGFR categories, with particularly low mean hemoglobin observed in women from Asian and African cohorts. Across the eGFR range, women had a lower hemoglobin compared to men, even at an eGFR of 15 ml/min (mean difference 5.3 g/l, 95% confidence interval [CI] 3.7-6.9). Lower eGFR, female sex, older age, lower body mass index, and diabetic kidney disease were all independent predictors of a lower hemoglobin value; however, this only explained a minority of variance (R2 7%-44% across cohorts).

Conclusion

There are substantial regional differences in hemoglobin distribution among individuals with CKD, and the majority of variance is unexplained by demographics, eGFR, or comorbidities. These findings call for a renewed interest in improving our understanding of hemoglobin determinants in specific CKD populations.

Impaired Renal Function and Major Cardiovascular Events in Young Adults

BACKGROUND

Cardiovascular (CV) disease in young adults (aged 18-39 years) is on the rise. Whether subclinical reductions in kidney function (ie, estimated glomerular filtration rate [eGFR] above the current threshold for chronic kidney disease but below age-expected values) are associated with elevated CV risk is unknown.

OBJECTIVES

The goal of this study was to examine age-specific associations of subclinical eGFR reductions in young adults with major adverse cardiovascular events (MACEs) and MACE plus heart failure (MACE+).

METHODS

A retrospective cohort study of 8.7 million individuals (3.6 million aged 18-39 years) was constructed using linked provincial health care data sets from Ontario, Canada (January 2008-March 2021). Cox models were used to examine the association of categorized eGFR (50-120 mL/min/1.73 m2) with MACE (first of CV mortality, acute coronary syndrome, and ischemic stroke) and MACE+, stratified according to age (18-39, 40-49, and 50-65 years).

RESULTS

In the study cohort (mean age 41.3 years; mean eGFR 104.2 mL/min/1.73 m2; median follow-up 9.2 years), a stepwise increase in the relative risk of MACE and MACE+ was observed as early as eGFR <80 mL/min/1.73 m2 in young adults (eg, for MACE, at eGFR 70-79 mL/min/1.73 m2, ages 18-30 years: 2.37 events per 1,000 person years [HR: 1.31; 95% CI: 1.27-1.40]; ages 40-49 years: 6.26 events per 1,000 person years [HR: 1.09; 95% CI: 1.06-1.12]; ages 50-65 years: 14.9 events per 1,000 person years [HR: 1.07; 95% CI: 1.05-1.08]). Results persisted for each MACE component and in additional analyses (stratifying according to past CV disease, accounting for albuminuria at index, and using repeated eGFR measures).

CONCLUSIONS

In young adults, eGFR below age-expected values were associated with an elevated risk for MACE and MACE+, warranting age-appropriate risk stratification, proactive monitoring, and timely intervention.

Risk of venous thromboembolism or hemorrhage among individuals with chronic kidney disease on prophylactic anticoagulant after hip or knee arthroplasty

Chronic kidney disease (CKD) confers a high risk of thrombosis and bleeding. However, little evidence exists regarding the optimal choice of postoperative thromboprophylaxis in these patients. We conducted a population-based, retrospective cohort study among adults ≥66 years old with CKD undergoing hip or knee arthroplasty who had filled an outpatient prophylactic anticoagulant prescription between 2010 and 2020 in Ontario, Canada. The primary outcomes of venous thrombosis (VTE) and hemorrhage were identified by validated algorithms using relevant diagnoses and billing codes. Overlap-weighted cause-specific Cox proportional hazard models were used to examine the association of direct oral anticoagulants (DOAC) on the 90-day risk of VTE and hemorrhage compared with low-molecular-weight heparin (LMWH). A total of 27  645 patients were prescribed DOAC (N = 22  943) or LMWH (N = 4702) after arthroplasty. Rivaroxaban was the predominant DOAC (94.5%), while LMWH mainly included enoxaparin (67%) and dalteparin (31.5%). DOAC users had higher eGFRs, fewer co-morbidities, and surgery in more recent years compared to LMWH users. After weighing, DOAC (compared with LMWH) was associated with a lower risk of VTE (DOAC: 1.5% vs. LMWH: 2.1%, weighted hazard ratio [HR] 0.75, 95% confidence interval [CI] 0.59-0.94) and a higher risk of hemorrhage (DOAC: 1.3% vs. LMWH: 1.0%, weighted HR 1.44, 95% CI 1.04-1.99). Additional analyses including a more stringent VTE defining algorithm, different eGFR cut-offs, and limiting to rivaroxaban and enoxaparin showed consistent findings. Among elderly adults with CKD, DOAC was associated with a lower VTE risk and a higher hemorrhage risk compared to LMWH following hip or knee arthroplasty.

Biomarkers in acute kidney injury: On the cusp of a new era?

The field of nephrology has been slow in moving beyond the utilization of creatinine as an indicator for chronic kidney disease and acute kidney injury (AKI). Early diagnosis and establishment of etiology, in particular, are important for treatment of AKI. In the setting of hospital-acquired AKI, tubular injury is more common, but acute interstitial nephritis (AIN) has a more treatable etiology. However, it is likely that AIN is under- or misdiagnosed due to current strategies that largely rely on clinical gestalt. In this issue of the JCI, Moledina and colleagues made an elegant case for the chemokine called C-X-C motif ligand 9 (CXCL9) as a biomarker of AIN. The authors used urine proteomics and tissue transcriptomics in patients with and without AIN to identify CXCL9 as a promising, noninvasive, diagnostic biomarker of AIN. These results have clinical implications that should catalyze future research and clinical trials in this space.

Managing Hyperkalemia in the Modern Era: A Case-Based Approach

The last decade has seen tremendous advances in the prevention and treatment of recurrent hyperkalemia. In this narrative review, we aim to highlight contemporary data on key areas in the epidemiology and management of hyperkalemia. Focusing on drug-induced hyperkalemia (the implications of renin-angiotensin-aldosterone system inhibitors [RAASi] discontinuation and the role of mineralocorticoid receptor antagonists), newer concurrent therapies that modify potassium handling (sodium-glucose transporter 2 inhibitors [SGLT2i]), the introduction of new treatment agents (oral potassium binding agents), and the controversial role of dietary potassium restriction, we apply recent research findings and review the evidence in a case-based format.

Associations between modest reductions in kidney function and adverse outcomes in young adults: retrospective, population based cohort study

OBJECTIVE

To study age specific associations of modest reductions in estimated glomerular filtration rate (eGFR) with adverse outcomes.

DESIGN

Retrospective, population based cohort study.

SETTING

Linked healthcare administrative datasets in Ontario, Canada.

PARTICIPANTS

Adult residents (18-65 years) with at least one outpatient eGFR value (categorized in 10 unit increments from 50 mL/min/1.73m2 to >120 mL/min/1.73m2), with no history of kidney disease.

MAIN OUTCOME MEASURES

eGFRs and hazard ratios of composite adverse outcome (all cause mortality, any cardiovascular event, and kidney failure) stratified by age (18-39 years, 40-49 years, and 50-65 years), and relative to age specific eGFR referents (100-110 mL/min/1.73m2) for ages 18-39 years, 90-100 for 40-49 years, 80-90 for 50-65 years).

RESULTS

From 1 January 2008 to 31 March 2021, among 8 703 871 adults (mean age 41.3 (standard deviation 13.6) years; mean index eGFR 104.2 mL/min/1.73m2 (standard deviation 16.1); median follow-up 9.2 years (interquartile range 5.7-11.4)), modestly reduced eGFR measurements specific to age were recorded in 18.0% of those aged 18-39, 18.8% in those aged 40-49, and 17.0% in those aged 50-65. In comparison with age specific referents, adverse outcomes were consistently higher by hazard ratio and incidence for ages 18-39 compared with older groups across all eGFR categories. For modest reductions (eGFR 70-80 mL/min/1.73m2), the hazard ratio for ages 18-39 years was 1.42 (95% confidence interval 1.35 to 1.49), 4.39 per 1000 person years; for ages 40-49 years was 1.13 (1.10 to 1.16), 9.61 per 1000 person years; and for ages 50-65 years was 1.08 (1.07 to 1.09), 23.4 per 1000 person years. Results persisted for each individual outcome and in many sensitivity analyses.

CONCLUSIONS

Modest eGFR reductions were consistently associated with higher rates of adverse outcomes. Higher relative hazards were most prominent and occurred as early as eGFR <80 mL/min/1.73m2 in younger adults, compared with older groups. These findings suggest a role for more frequent monitoring of kidney function in younger adults to identify individuals at risk to prevent chronic kidney disease and its complications.

Recent updates in kidney risk prediction modeling: novel approaches and earlier outcomes

PURPOSE OF REVIEW

Recent years have witnessed the development of kidney risk prediction models which diverge from traditional model designs to incorporate novel approaches along with a focus on earlier outcomes. This review summarizes these recent advances, evaluates their pros and cons, and discusses their potential implications.

RECENT FINDINGS

Several kidney risk prediction models have recently been developed utilizing machine learning rather than traditional Cox regression. These models have demonstrated accurate prediction of kidney disease progression, often beyond that of traditional models, in both internal and external validation. On the opposite end of the spectrum, a simplified kidney risk prediction model was recently developed which minimized the need for laboratory data and instead relies primarily on self-reported data. While internal testing showed good overall predictive performance, the generalizability of this model remains uncertain. Finally, there is a growing trend toward prediction of earlier kidney outcomes (e.g., incident chronic kidney disease [CKD]) and away from a sole focus on kidney failure.

SUMMARY

Newer approaches and outcomes now being incorporated into kidney risk prediction modeling may enhance prediction and benefit a broader patient population. However, future work should address how best to implement these models into practice and assess their long-term clinical effectiveness.

Overcoming the blood brain barrier in glioblastoma: Status and future perspective

Glioblastoma is the most common primary brain malignancy in adults. Treatment of glioblastoma patients is based on neurosurgery, radiation therapy and chemotherapy. Despite this multimodal therapeutic regimen, the prognosis of glioblastoma patients is poor. Indeed, glioblastoma is very resistant to treatments due to multiple molecular and cellular mechanisms including the existence of the blood-brain barrier (BBB). The BBB consists of multiple layers surrounding brain vessels and limits drug penetration within the brain. Therefore, overcoming the BBB is a strategy to increase bioavailability and efficacy of therapeutic agents against glioblastoma cells. The development of two approaches is ongoing: i) enhancing the delivery of drugs to the brain and ii) improving the penetration of drugs into the brain. One way to enhance drug delivery to the brain is through high-dose intravenous chemotherapy, with or without bone marrow transplantation, or via intra-arterial chemotherapy, with or without disrupting the BBB through osmotic means. Conversely, improving drug penetration within the brain can be achieved through modifying either the drug itself or the BBB. Promising results in terms of safety and signals of efficacy were obtained with these approaches in early phase clinical trials. More advanced comparative clinical trials are needed to investigate the clinical benefit for glioblastoma patients.

Management of Intermittent Hemodialysis in the Critically Ill Patient

Intermittent hemodialysis remains a cornerstone of extracorporeal KRT in the intensive care unit, either as a first-line therapy for AKI or a second-line therapy when patients transition from a continuous or prolonged intermittent therapy. Intermittent hemodialysis is usually provided 3 days per week in this setting on the basis that no clinical benefits have been demonstrated with more frequent hemodialysis. This should not detract from the importance of continually assessing and refining the hemodialysis prescription (including the need for extra treatments) according to dynamic changes in extracellular volume and other parameters, and ensuring that an adequate dose of hemodialysis is being delivered to the patient. Compared with other KRT modalities, the cardinal challenge encountered during intermittent hemodialysis is hemodynamic instability. This phenomenon occurs when reductions in intravascular volume, as a consequence of ultrafiltration and/or osmotic shifts, outpace compensatory plasma refilling from the extravascular space. Myocardial stunning, triggered by intermittent hemodialysis, and independent of ultrafiltration, may also contribute. The hemodynamic effect of intermittent hemodialysis is likely magnified in patients who are critically ill due to an inability to mount sufficient compensatory physiologic responses in the context of multiorgan dysfunction. Of the many interventions that have undergone testing to mitigate hemodynamic instability related to KRT, the best evidence exists for cooling the dialysate and raising the dialysate sodium concentration. Unfortunately, the evidence supporting routine use of these and other interventions is weak owing to poor study quality and limited sample sizes. Intermittent hemodialysis will continue to be an important and commonly used KRT modality for AKI in patients with critical illness, especially in jurisdictions where resources are limited. There is an urgent need to harmonize the definition of hemodynamic instability related to KRT in clinical trials and robustly test strategies to combat it in this vulnerable patient population.

Predictors of serum vancomycin levels in peritoneal dialysis-associated peritonitis

BACKGROUND

Intraperitoneal (IP) vancomycin is often first-line empiric therapy for peritoneal dialysis (PD) peritonitis; however, whether dosing should be adjusted for patient-specific characteristics remains unclear. We sought to identify factors associated with the day 3 vancomycin serum level in patients receiving vancomycin for PD peritonitis.

METHODS

Retrospective single-centre adult cohort of 58 patients with PD peritonitis treated with IP vancomycin between January 2016 and May 2022. Linear regression was used to examine the association between day 3 vancomycin level and candidate predictors including age, sex, weight, glomerular filtration rate (GFR), urea and creatinine clearance (total, residual, dialysate), PD modality, peritoneal solute transfer rate and initial vancomycin dose. Logistic regression was used to evaluate the likelihood of achieving a level (≥15 mg/L) associated with these predictor variables.

RESULTS

A 2-g loading dose was given in 51 cases, and 38 patients (66%) had a therapeutic day 3 level. Each 5 mg/kg increase in initial vancomycin dose was associated with a 1.38 mg/L (95% confidence interval 0.52, 2.23) increase in day 3 level. Each 1 mL/min increase in GFR was associated with a 0.29 mg/L decrease (95% confidence interval 0.05, 0.52) in day 3 level. The likelihood of achieving a therapeutic level was approximately four times higher with an initial dose of ≥25 mg/kg compared to <25 mg/kg (odds ratio 3.75, 95% confidence interval 1.05, 13.46).

CONCLUSIONS

Following an average 2-g vancomycin loading dose for suspected PD peritonitis, one-third of patients were subtherapeutic on day 3. GFR and weight-based dosing were independently associated with day 3 vancomycin level, and their consideration could improve the likelihood of achieving an early therapeutic level.

The Risk of Cardiovascular Events in Individuals With Primary Glomerular Diseases

RATIONALE & OBJECTIVE

Little is known about the risk of cardiovascular disease (CVD) in patients with various primary glomerular diseases. In a population-level cohort of adults with primary glomerular disease, we sought to describe the risk of CVD compared with the general population and the impact of traditional and kidney-related risk factors on CVD risk.

STUDY DESIGN

Observational cohort study.

SETTING & PARTICIPANTS

Adults with membranous nephropathy (n = 387), minimal change disease (n = 226), IgA nephropathy (n = 759), and focal segmental glomerulosclerosis (n = 540) from a centralized pathology registry in British Columbia, Canada (2000-2012).

EXPOSURE

Traditional CVD risk factors (diabetes, age, sex, dyslipidemia, hypertension, smoking, prior CVD) and kidney-related risk factors (type of glomerular disease, estimated glomerular filtration rate [eGFR], proteinuria).

OUTCOME

A composite CVD outcome of coronary artery, cerebrovascular, and peripheral vascular events, and death due to myocardial infarction or stroke.

ANALYTICAL APPROACH

Subdistribution hazards models to evaluate the outcome risk with non-CVD death treated as a competing event. Standardized incidence rates (SIR) calculated based on the age- and sex-matched general population.

RESULTS

During a median 6.8 years of follow-up, 212 patients (11.1%) experienced the CVD outcome (10-year risk, 14.7% [95% CI, 12.8%-16.8%]). The incidence rate was high for the overall cohort (24.7 per 1,000 person-years) and for each disease type (range, 12.2-46.1 per 1,000 person-years), and was higher than that observed in the general population both overall (SIR, 2.46 [95% CI, 2.12-2.82]) and for each disease type (SIR range, 1.38-3.98). Disease type, baseline eGFR, and proteinuria were associated with a higher risk of CVD and, when added to a model with traditional risk factors, led to improvements in model fit (R² of 14.3% vs 12.7%), risk discrimination (C-statistic of 0.81 vs 0.78; difference, 0.02 [95% CI, 0.01-0.04]), and continuous net reclassification improvement (0.4 [95% CI, 0.2-0.6]).

LIMITATIONS

Ascertainment of outcomes and comorbidities using administrative data.

CONCLUSIONS

Patients with primary glomerular disease have a high absolute risk of CVD that is approximately 2.5 times that of the general population. Consideration of eGFR, proteinuria, and type of glomerular disease may improve risk stratification of CVD risk in these individuals.

PLAIN-LANGUAGE SUMMARY

Patients with chronic kidney disease are known to be at high risk of cardiovascular disease. Cardiovascular risk in patients with primary glomerular diseases is poorly understood because these conditions are rare and require a kidney biopsy for diagnosis. In this study of 1,912 Canadian patients with biopsy-proven IgA nephropathy, minimal change disease, focal segmental glomerulosclerosis, and membranous nephropathy, the rate of cardiovascular events was 2.5 times higher than in the general population and was high for each disease type. Consideration of disease type, kidney function, and proteinuria improved the prediction of cardiovascular events. In summary, our population-level study showed that patients with primary glomerular diseases have a high cardiovascular risk, and that inclusion of kidney-specific risk factors may improve risk stratification.

A Population-Based Analysis of the Risk of Glomerular Disease Relapse after COVID-19 Vaccination

BACKGROUND

Although case reports have described relapses of glomerular disease after COVID-19 vaccination, evidence of a true association is lacking. In this population-level analysis, we sought to determine relative and absolute risks of glomerular disease relapse after COVID-19 vaccination.

METHODS

In this retrospective population-level cohort study, we used a centralized clinical and pathology registry (2000-2020) to identify 1105 adult patients in British Columbia, Canada, with biopsy-proven glomerular disease that was stable on December 14, 2020 (when COVID-19 vaccines first became available). The primary outcome was disease relapse, on the basis of changes in kidney function, proteinuria, or both. Vaccination was modeled as a 30-day time-varying exposure in extended Cox regression models, stratified on disease type.

RESULTS

During 281 days of follow-up, 134 (12.1%) patients experienced a relapse. Although a first vaccine dose was not associated with relapse risk (hazard ratio [HR]=0.67; 95% confidence interval [95% CI], 0.33 to 1.36), exposure to a second or third dose was associated with a two-fold risk of relapse (HR=2.23; 95% CI, 1.06 to 4.71). The pattern of relative risk was similar across glomerular diseases. The absolute increase in 30-day relapse risk associated with a second or third vaccine dose varied from 1%-2% in ANCA-related glomerulonephritis, minimal change disease, membranous nephropathy, or FSGS to 3%-5% in IgA nephropathy or lupus nephritis. Among 24 patients experiencing a vaccine-associated relapse, 4 (17%) had a change in immunosuppression, and none required a biopsy.

CONCLUSIONS

In a population-level cohort of patients with glomerular disease, a second or third dose of COVID-19 vaccine was associated with higher relative risk but low absolute increased risk of relapse.

The value of repeat kidney biopsy during an atypical course of membranous nephropathy

Background

The clinical trajectory for patients with primary membranous nephropathy ranges widely from spontaneous remission to a rapid decline in kidney function. Etiologies for rapid progression with membranous nephropathy include concurrent bilateral renal vein thrombosis, malignant hypertension, and crescentic membranous nephropathy. Given the wide heterogeneity in prognosis, timing of immunosuppressive therapy is often challenging and centers around an individual patient’s perceived risk for rapidly progressive disease.

Case presentation

Herein, we describe the clinical course of a young patient who initially developed a typical presentation of membranous nephropathy with consistent kidney biopsy findings. Given clinical stability, a six month observation period was undertaken prior to initiating immunosuppression. Within this observation window, the patient developed community acquired pneumonia followed several weeks later by a sudden, rapid decline in kidney function requiring dialysis. Repeat kidney biopsy revealed post-infectious glomerulonephritis superimposed upon a background of membranous nephropathy. Immunosuppressive therapy resulted in a favorable long-term outcome with normalization of kidney function and remission of nephrotic syndrome. To our knowledge, this is the first report of the simultaneous occurrence of these two glomerular disease processes.

Conclusion

This case illustrates the value of repeat kidney biopsy during an atypical course of membranous nephropathy. Superimposed glomerular disease processes should be considered during a course of rapidly progressive membranous nephropathy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-022-02863-y.

Contemporary risk prediction models in chronic kidney disease: when less is more

PURPOSE OF REVIEW

Clinicians have an ever-increasing number of prediction tools at their disposal for estimating the risk of kidney failure in their patients. This review aims to summarize contemporary evidence for chronic kidney disease (CKD) risk prediction models across the spectrum of kidney function, and explore nuances in the interpretation of risk estimates.

RECENT FINDINGS

A European study using predominantly laboratory data has extended kidney failure prediction to patients with more preserved estimated glomerular filtration rate. For older patients with advanced CKD, prediction tools that censor for death (such as the Kidney Failure Risk Equation) overestimate the risk of kidney failure, especially over time horizons longer than 2 years. This problem can be addressed by accounting for the competing risk of death, as shown in well designed validation studies. The clinical utility of kidney failure risk prediction tools is being increasingly tested at a population level to inform policy and referral guidelines.

SUMMARY

There is welcome trend to validate existing prediction tools in diverse clinical settings and identify their role in clinical practice. Clinicians should be cognizant of overestimating kidney failure risk in older patients with advanced CKD due to the competing risk of death. For moderate CKD and for short-term predictions, the Kidney Failure Risk Equation remains the most widely validated prediction tool.

Intravenous albumin for the prevention of hemodynamic instability during sustained low-efficiency dialysis: a randomized controlled feasibility trial (The SAFER-SLED Study)

Background

Hemodynamic instability is a frequent complication of sustained low-efficiency dialysis (SLED) treatments in the ICU. Intravenous hyperoncotic albumin may prevent hypotension and facilitate ultrafiltration. In this feasibility trial, we sought to determine if a future trial, powered to evaluate clinically relevant outcomes, is feasible.

Methods

This single-center, blinded, placebo-controlled, randomized feasibility trial included patients with acute kidney injury who started SLED in the ICU. Patients were randomized to receive 25% albumin versus 0.9% saline (control) as 100 mL boluses at the start and midway through SLED, for up to 10 sessions. The recruitment rate and other feasibility outcomes were determined. Secondary exploratory outcomes included ultrafiltration volumes and metrics of hemodynamic instability.

Results

Sixty patients (271 SLED sessions) were recruited over 10 months. Age and severity of illness were similar between study groups. Most had septic shock and required vasopressor support at baseline. Protocol adherence occurred for 244 sessions (90%); no patients were lost to follow-up; no study-related adverse events were observed; open label albumin use was 9% and 15% in the albumin and saline arms, respectively. Ultrafiltration volumes were not significantly different. Compared to the saline group, the albumin group experienced less hemodynamic instability across all definitions assessed including a smaller absolute decrease in systolic blood pressure (mean difference 10.0 mmHg, 95% confidence interval 5.2–14.8); however, there were significant baseline differences in the groups with respect to vasopressor use prior to SLED sessions (80% vs 61% for albumin and saline groups, respectively).

Conclusions

The efficacy of using hyperoncotic albumin to prevent hemodynamic instability in critically ill patients receiving SLED remains unclear. A larger trial to evaluate its impact in this setting, including evaluating clinically relevant outcomes, is feasible.

Trial registration ClinicalTrials.gov (NCT03665311); First Posted: Sept 11th, 2018. https://clinicaltrials.gov/ct2/show/NCT03665311?term=NCT03665311&draw=2&rank=1

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-021-00962-x.

Association of anti-neutrophil cytoplasmic antibody-associated vasculitis and cardiovascular events: a population-based cohort study

Background

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is implicated in elevating the risk for cardiovascular (CV) disease; whether the elevated risk applies to all types of CV diseases or specific types is unclear. This study examined the association of AAV and adverse CV outcomes compared with the non-AAV population.

Methods

We conducted a population-based, retrospective cohort study of adults (mean age 61 years, 51% female) with a new diagnosis of AAV in Ontario, Canada from 2007 to 2017. Weighted models were used to examine the association of AAV (n = 1520) and CV events in a matched (1:4) control cohort (n = 5834). The main outcomes were major adverse CV events (MACE), defined as myocardial infarction (MI), stroke or CV death, its components, atrial fibrillation (AF) and congestive heart failure (CHF).

Results

Over a mean follow-up of 3.8 years, AAV (compared with non-AAV) was associated with a higher risk of stroke: cumulative incidence 7.0% versus 5.2%, sub-distribution hazard ratio (sHR) 1.49 [(95% confidence interval (95% CI) 1.10–2.02]; AF: cumulative incidence 16.4% versus 11.5%, sHR 1.51, 95% CI 1.30–1.75; and CHF: cumulative incidence 20.8% versus 13.3%, sHR 1.41, 95% CI 1.22–1.62; but not for MACE, MI or CV death. The risks for all CV events, except CV death, were significantly elevated in the early period after AAV diagnosis, in particular AF (365-day sHR 2.06, 95% CI 1.71–2.48; 90-day sHR 3.33, 95% CI 2.66–4.18) and CHF (365-day sHR 1.75, 95% CI 1.48–2.07; 90-day sHR 2.65, 95% CI 2.15–3.26).

Conclusion

AAV is associated with a high risk of certain types of CV events, particularly in the early period following diagnosis.

Proteinuria and venous thromboembolism in pregnancy: a population-based cohort study

Background

Pregnancy-associated venous thromboembolism (VTE) is associated with high morbidity and mortality. Identification of risk factors of VTE may lead to improved maternal and foetal outcomes. Proteinuria confers a pro-thrombotic state, however, its association with VTE in pregnancy remains unknown. We set out to assess the association of proteinuria and VTE during pregnancy.

Methods

We conducted a population-based, retrospective cohort study of all pregnant women (≥16 years of age) with a proteinuria measure within 20 weeks of conception (n = 306 244; mean age 29.8 years) from Ontario, Canada. Proteinuria was defined by any of the following: urine albumin:creatinine ratio ≥3 mg/mmol, urine protein:creatinine ratio ≥5 mg/mmol or urine dipstick proteinuria ≥1. The main outcome measure was a diagnosis of VTE up to 24-weeks post-partum.

Results

A positive proteinuria measurement occurred in 8508 (2.78%) women and was more common with a history of kidney disease, gestational or non-gestational diabetes mellitus and hypertension. VTE events occurred in 625 (0.20%) individuals, with a higher risk among women with positive proteinuria [32 events (0.38%)] compared with women without proteinuria [593 events (0.20%); inverse probability-weighted risk ratio 1.79 (95% confidence interval 1.25-2.57)]. The association was consistent using a more specific VTE definition, in the post-partum period, in high-risk subgroups (hypertension or diabetes) and when the sample was restricted to women with preserved kidney function.

Conclusions

The presence of proteinuria in the first 20 weeks of pregnancy is associated with a significantly higher risk of VTE.

Comparison of Clinical Outcomes and Safety Associated With Chlorthalidone vs Hydrochlorothiazide in Older Adults With Varying Levels of Kidney Function

IMPORTANCE

Thiazide diuretics are commonly prescribed for the treatment of hypertension, a disease highly prevalent among older individuals and in those with chronic kidney disease. How specific thiazide diuretics compare in regard to safety and clinical outcomes in these populations remains unknown.

OBJECTIVE

To compare safety and clinical outcomes associated with chlorthalidone or hydrochlorothiazide use among older adults with varying levels of kidney function.

DESIGN, SETTING, AND PARTICIPANTS

This population-based retrospective cohort study was conducted in Ontario, Canada, from 2007 to 2015. Participants included adults aged 66 years or older who initiated chlorthalidone or hydrochlorothiazide during this period. Data were analyzed from December 2019 through September 2020.

EXPOSURES

New chlorthalidone users were matched 1:4 with new hydrochlorothiazide users by a high-dimensional propensity score. Time-to-event models accounting for competing risks examined the associations between chlorthalidone vs hydrochlorothiazide use and the outcomes of interest overall and within estimated glomerular filtration rate (eGFR) categories (≥60, 45-59, and <45 mL/min/1.73 m2).

MAIN OUTCOMES AND MEASURES

The outcomes of interest were adverse kidney events (ie, eGFR decline ≥30%, dialysis, or kidney transplantation), cardiovascular events (composite of myocardial infarction, coronary revascularization, heart failure, or atrial fibrillation), all-cause mortality, and electrolyte anomalies (ie, sodium or potassium levels outside reference ranges).

RESULTS

After propensity score matching, the study cohort included 12 722 adults (mean [SD] age, 74 [7] years; 7063 [56%] women; 5659 [44%] men; mean [SD] eGFR, 69 [19] mL/min/1.73 m2), including 2936 who received chlorthalidone and 9786 who received hydrochlorothiazide. Chlorthalidone use was associated with a higher risk of eGFR decline of 30% or greater (hazard ratio [HR], 1.24 [95% CI, 1.13-1.36]) and cardiovascular events (HR, 1.12 [95% CI, 1.04-1.22]) across all eGFR categories compared with hydrochlorothiazide use. Chlorthalidone use was also associated with a higher risk of hypokalemia compared with hydrochlorothiazide use, which was more pronounced among those with higher eGFR (eGFR ≥60 mL/min/1.73 m2: HR, 1.86 [95% CI, 1.67-2.08]; eGFR 45-59 mL/min/1.73 m2: HR, 1.57 [95% CI, 1.25-1.96]; eGFR <45 mL/min/1.73 m2: HR, 1.10 [95% CI, 0.84-1.45]; P for interaction = .001). No significant differences were observed between chlorthalidone and hydrochlorothiazide for dialysis or kidney transplantation (HR, 1.44 [95% CI, 0.88-2.36]), all-cause mortality (HR, 1.10 [95% CI, 0.93-1.29]), hyperkalemia (HR, 1.05 [95% CI, 0.79-1.39]), or hyponatremia (HR, 1.14 [95% CI, CI 0.98-1.32]).

CONCLUSIONS AND RELEVANCE

This cohort study found that among older adults, chlorthalidone use was associated with a higher risk of eGFR decline, cardiovascular events, and hypokalemia compared with hydrochlorothiazide use. The excess risk of hypokalemia with chlorthalidone was attenuated in participants with reduced kidney function. Placed in context with prior observational studies comparing the safety and clinical outcomes associated with thiazide diuretics, these results suggest that there is no evidence to prefer chlorthalidone over hydrochlorothiazide.

Perceptions of Multidisciplinary Renal Team Members toward Home Dialysis Therapies

Background

Patients with ESKD are encouraged to pursue home dialysis therapy with the aims of improving quality of life, increasing patient autonomy, and reducing cost to health care systems. In a multidisciplinary team setting, patients interact with nephrologists, nurses, and allied health staff, all of whom may influence a patient's modality choice. Our objective was to evaluate the perceptions of all renal team members toward home dialysis therapies.

Methods

We performed a cross-sectional survey of multidisciplinary renal team members across five renal programs in British Columbia, Canada. The survey contained questions regarding primary work area, modality preference, patient and system factors that may influence modality candidacy, perceived knowledge of home therapies, and need for further education.

Results

A total of 334 respondents (22 nephrologists, 172 hemodialysis nurses, 49 home nurses, 20 predialysis nurses, and 71 allied health staff) were included (48% response rate). All respondents felt that home dialysis was beneficial for patients who work or study, improved patients' quality of life, and provided cost savings to the system. Compared with in-center hemodialysis nurses, home therapies nurses were between five and nine times more likely to favor a home therapy for patients of older age, lower socioeconomic status, lower educational level, higher burden of comorbidities, and those lacking social supports. Nephrologists and patients were felt to have the most influence on modality choice, whereas dialysis nurses were seen as having the least effect on modality choice. Most respondents felt the need for further education in home therapies.

Conclusions

The majority of multidisciplinary team members, including allied health staff, acknowledged the benefits of home therapies. There were significant discrepancies among team members regarding patient-/system-level factors that may affect the candidacy of home therapies. Structured, focused, and repeated education sessions for all renal team members may help to address misperceptions around factors that influence modality candidacy.

Initial and Recurrent Hyperkalemia Events in Patients With CKD in Older Adults: A Population-Based Cohort Study

Background:

The risk of hyperkalemia is elevated in chronic kidney disease (CKD); however, the initial and recurrent risk among older individuals is less clear.

Objectives:

We set out to examine the initial and 1-year recurrent risk of hyperkalemia by level of kidney function (estimated glomerular filtration rate, eGFR) in older adults (≥66 years old).

Design:

Population-based, retrospective cohort study

Settings:

Ontario, Canada

Participants:

905 167 individuals (≥66 years old) from 2008 to 2015.

Measurements:

Serum potassium values

Methods:

Individuals were stratified by eGFR (≥90, 60-89, 30-59, 15-29 mL/min/1.73 m²) and examined for the risk of incident hyperkalemia (K ≥ 5.5 mEq/L) using adjusted Cox proportional hazards models. The 1-year risk of recurrent hyperkalemia was examined using multivariable Andersen-Gill models.

Results:

Among a population of 905 167 individuals (15% eGFR ≥ 90, 58% eGFR 60-89, 25% eGFR 30-59, 3% eGFR 15-29) with a potassium measurement, there were a total of 18 979 (2.1%) individuals with hyperkalemia identified. The event rate (per 1000 person-years) and adjusted hazard ratio (HR) of hyperkalemia was inversely associated with eGFR (mL/min; eGFR >90 mL/min: 8.8, referent, 60-89 mL/min: 11.8 HR 1.41; eGFR 30-59: 39.8, HR 4.37; eGFR 15-29: 133.6, 13.65) and with an increasing urine albumin-to-creatinine ratio (ACR, mg/mmol; ACR< 3: 14, referent, ACR 3-30: 35.1, HR 1.98; ACR >30: 93.7, 4.71). The 1-year event rate and adjusted risk of recurrent hyperkalemia was similarly inversely associated with eGFR (eGFR ≥ 90: 10.1, referent, eGFR 60-89: 14.4, HR 1.47; eGFR 30-59: 54.8, HR 4.90; eGFR 15-29: 208.0, HR 12.98). Among individuals with a baseline eGFR of 30 to 59 and 15 to 29, 0.9 and 3.8% had greater than 2 hyperkalemia events. The relative risk of initial and recurrent hyperkalemia was marginally higher with RAAS blockade. Roughly 1 in 4 individuals with hyperkalemia required hospitalization the day of or within 30 days after their hyperkalemia event.

Limitations:

Limited to individuals aged 66 years and above.

Conclusions:

Patients with low eGFR are at a high risk of initial and recurrent hyperkalemia.

Trial registration:

N/A

β-blockers in hemodialysis: simple questions, complicated answers

In this issue of the Clinical Kidney Journal, Wu et al. present the results of a nationwide population-based study using Taiwanese administrative data to compare safety and efficacy outcomes with initiation of bisoprolol versus carvedilol among patients receiving maintenance hemodialysis for >90 days. The primary outcomes were all-cause mortality and major adverse cardiovascular events over 2 years of follow-up. The study found that bisoprolol was associated with a lower risk for both major adverse cardiovascular events and all-cause mortality compared with carvedilol. While the bulk of the existing evidence favors a cardioprotective and survival benefit with β-blockers as a medication class among dialysis patients, there is wide heterogeneity among specific β-blockers in regard to pharmacologic properties and dialyzability. While acknowledging the constraints of observational data, these findings may serve to inform clinicians about the preferred β-blocker agent for dialysis patients to help mitigate cardiovascular risk and improve long-term survival for this high-risk population.

Quantifying Missed Opportunities for Recruitment to Home Dialysis Therapies

Background:

Despite the recognized benefits of home therapies for patients and the health care system, most individuals with kidney failure in Canada continue to be initiated on in-center hemodialysis. To optimize recruitment to home therapies, there is a need for programs to better understand the extent to which potential candidates are not successfully initiated on these therapies.

Objective:

We aimed to quantify missed opportunities to recruit patients to home therapies and explore where in the modality selection process this occurs.

Design:

Retrospective observational study.

Setting:

British Columbia, Canada.

Patients:

All patients aged >18 years who started chronic dialysis in British Columbia between January 01, 2015, and December 31, 2017. The sample was further restricted to include patients who received at least 3 months of predialysis care. All patients were followed for a minimum of 12 months from the start of dialysis to capture any transition to home therapies.

Methods:

Cases were defined as a “missed opportunity” if a patient had chosen a home therapy, or remained undecided about their preferred modality, and ultimately received in-center hemodialysis as their destination therapy. These cases were assessed for: (1) documentation of a contraindication to home therapies; and (2) the type of dialysis education received. Differences in characteristics among patients classified as an appropriate outcome or a missed opportunity were examined using Wilcoxon rank-sum test or χ² test, as appropriate.

Results:

Of the 1845 patients who started chronic dialysis during the study period, 635 (34%) were initiated on a home therapy. A total of 320 (17.3%) missed opportunities were identified, with 165 (8.9%) having initially chosen a home therapy and 155 (8.4%) being undecided about their preferred modality. Compared with patients who chose and initiated or transitioned to a home therapy, those identified as a missed opportunity tended to be older with a higher prevalence of cardiovascular disease. A contraindication to both peritoneal dialysis and home hemodialysis was documented in 8 “missed opportunity” patients. General modality orientation was provided to most (71%) patients who had initially chosen a home therapy but who ultimately received in-center hemodialysis. These patients received less home therapy–specific education compared with patients who chose and subsequently started a home therapy (20% vs 35%, P < .001).

Limitations:

Contraindications to home therapies were potentially under-ascertained, and the nature of contraindications was not systematically captured.

Conclusions:

Even within a mature home therapy program, we discovered a substantial number of missed opportunities to recruit patients to home therapies. Better characterization of modality contraindications and enhanced education that is specific to home therapies may be of benefit. Mapping the recruitment pathway in this way can define the magnitude of missed opportunities and identify areas that could be optimized. This is to be encouraged, as even small incremental improvements in the uptake of home therapies could lead to better patient outcomes and contribute to significant cost savings for the health care system.

Trial Registration:

Not applicable as this was a qualitative study.

Maintaining the Uptake of Peritoneal Dialysis During the COVID-19 Pandemic: A Research Letter

BACKGROUND

Due to inherent challenges in maintaining physical distancing in hemodialysis units, the Canadian Society of Nephrology has recommended peritoneal dialysis as the preferred modality for patients requiring maintenance dialysis during the coronavirus disease 19 (COVID-19) pandemic. However, pursuing peritoneal dialysis is not without risk due to the requirement for in-person contact during catheter insertion and training, and there is a paucity of data regarding the experience of peritoneal dialysis during the early phases of the pandemic.

OBJECTIVE

To examine the incidence and outcomes of peritoneal dialysis between March 17 and June 01, 2020 compared to the same time period in preceding years.

DESIGN

Retrospective observational study.

SETTING

British Columbia, Canada. After the pandemic was declared on March 17, 2020, patients continued to be trained in peritoneal dialysis. In an effort to limit time spent in hospital, patients were preferentially trained in continuous ambulatory peritoneal dialysis, training times were truncated for some patients, and peritoneal dialysis catheters were inserted by a physician at the bedside whenever feasible.

PATIENTS

All patients aged >18 years who started chronic maintenance dialysis during the period March 17 to June 01 in the years 2018 to 2020 inclusive. The time period was extended to include the years 2010 to 2020 inclusive to evaluate longer term trends in dialysis incidence.

MEASUREMENTS

A provincial clinical information system was used to capture the date of commencing dialysis, dialysis modality, and complications including peritonitis. Overall uptake of peritoneal dialysis included new starts and transitions to peritoneal dialysis from in-center hemodialysis during the observation period.

METHODS

The incidence of dialysis during the specified time period, overall and by modality, was calculated per million population using census figures for the population at risk. Patients were followed for a minimum of 30 days from the start of peritoneal dialysis to capture episodes of peritonitis and COVID-19.

RESULTS

A total of 211 patients started maintenance dialysis between March 17 and June 01, 2020. The incidence dialysis rate (41.3 per million population) was lower than that expected based on the 10-year trend from 2010 to 2019 inclusive (expected rate 45.7 per million population, 95% confidence interval 41.7 to 50.1). A total of 93 patients started peritoneal dialysis, including 32 patients who transitioned from in-center hemodialysis, contributing to a higher overall uptake of peritoneal dialysis compared to preceding years. The incidence rate for peritoneal dialysis of 18.2 per million population was higher than that expected (16.3 per million population, 95% confidence interval 14.0 to 19.0). Half of patients (48%) underwent a bedside peritoneal dialysis catheter insertion by a physician. During 30 days of follow-up, 2 (2.2%) patients experienced peritonitis and no patients were diagnosed with COVID-19.

LIMITATIONS

Results are short term and generalizable only to regions with similarly low community rates of transmission of severe acute respiratory syndrome coronavirus 2.

CONCLUSIONS

These preliminary findings indicate that peritoneal dialysis can be safely started and perhaps expanded as a means of mitigating the anticipated surge in in-center hemodialysis during the COVID-19 pandemic. Important contributors to the uptake of peritoneal dialysis in British Columbia were bedside catheter insertions and expediting transitions from in-center hemodialysis to peritoneal dialysis.

Quantifying Duration of Proteinuria Remission and Association with Clinical Outcome in IgA Nephropathy

BACKGROUND

On the basis of findings of observational studies and a meta-analysis, proteinuria reduction has been proposed as a surrogate outcome in IgA nephropathy. How long a reduction in proteinuria needs to be maintained to mitigate the long-term risk of disease progression is unknown.

METHODS

In this retrospective multiethnic cohort of adult patients with IgA nephropathy, we defined proteinuria remission as a ≥25% reduction in proteinuria from the peak value after biopsy, and an absolute reduction in proteinuria to <1 g/d. The exposure of interest was the total duration of first remission, treated as a time-varying covariate using longitudinal proteinuria measurements. We used time-dependent Cox proportional hazards regression models to quantify the association between the duration of remission and the primary outcome (ESKD or a 50% reduction in eGFR).

RESULTS

During a median follow-up of 3.9 years, 274 of 1864 patients (14.7%) experienced the primary outcome. The relationship between duration of proteinuria remission and outcome was nonlinear. Each 3 months in sustained remission up to approximately 4 years was associated with an additional 9% reduction in the risk of disease progression (hazard ratio [HR], 0.91; 95% confidence interval [95% CI], 0.89 to 0.93). Thereafter, each additional 3 months in remission was associated with a smaller, nonsignificant risk reduction (HR, 0.99; 95% CI, 0.96 to 1.03). These findings were robust to multivariable adjustment and consistent across clinical and histologic subgroups.

CONCLUSIONS

Our findings support the use of proteinuria as a surrogate outcome in IgA nephropathy, but additionally demonstrate the value of quantifying the duration of proteinuria remission when estimating the risk of hard clinical endpoints.

Temporal Trends in Hemoglobin, Use of Erythropoiesis Stimulating Agents, and Major Clinical Outcomes in Incident Dialysis Patients in Canada

Introduction

Several jurisdictions have adopted a more conservative approach to anemia in patients receiving dialysis amid safety concerns from target hemoglobin studies. It is largely unknown if this has contributed to a change in clinical outcomes.

Methods

A national registry was used to identify 35,945 adult patients who initiated and were maintained on dialysis for ≥90 days in Canada from January 2007 to December 2015. Outcomes were ascertained until March 2017 via linkage with hospital discharge diagnoses. Cox proportional hazards models were used to investigate the association between the era of dialysis initiation and the primary composite outcome (acute myocardial infarction [AMI], stroke, or mortality).

Results

The mean hemoglobin at dialysis initiation decreased from 102.9 g/l in 2007 to 95.5 g/l in 2015, corresponding with a higher prevalence of hemoglobin <80 g/l (8% to 17%) and a reduction in erythropoiesis stimulating agent (ESA) use (49% to 44%). After multivariable adjustment, Era 3 (2013–2015) was associated with an 8% relative risk reduction in the primary outcome compared with Era 1 (2007–2009) (hazard ratio [HR] 0.92, 95% confidence interval [CI] 0.88–0.96), a 10% relative reduction in mortality (HR 0.90, 95% CI 0.85–0.94) but no significant change in AMI or stroke. In a model without era, neither hemoglobin nor ESA use was an independent predictor of outcome.

Conclusion

There have been modest declines in average hemoglobin values and ESA use among incident dialysis patients in Canada with no change in major cardiovascular outcomes. Patient survival has improved over time, likely for reasons other than anemia management.

COVID-19 Status, Symptom Burden, and Characteristics of Dialysis Patients Residing in Areas of Community Transmission: Research Letter

Background

Routine testing of hemodialysis patients for COVID-19 (outside of those identified as "at risk" based on regional practice) is not universally recommended. However, there is variability in the clinical presentation of COVID-19; patients may experience symptoms that do not meet regional criteria for testing and some patients with active infection may be asymptomatic. To avoid missing individuals who are infected, consideration could be made for regular screening, particularly among those residing in areas with evidence of community spread.

Objective

To describe the clinical characteristics, symptom burden, and COVID-19 status in a cross-section of hemodialysis patients residing in areas with evidence of community spread.

Design

Cross-sectional study.

Setting

Three hemodialysis units in a large tertiary care facility in Nova Scotia, Canada.

Patients

In-center hemodialysis patients who resided in areas with evidence of community transmission at the time of the study.

Methods

All dialysis patients (irrespective of whether or not they resided in areas with community spread) completed a standard "at-risk" questionnaire for COVID-19 based on (1) 2 or more of new or worsening cough, fever greater than 38°C, sore throat, headache, runny nose/new or acute respiratory illness consistent with infection or (2) any one of close contact with a known/suspected case, travel outside of the province or residence in a facility with an outbreak prior to entry into the dialysis unit at each treatment. Patients residing in areas with evidence of community spread were swabbed for SARS-CoV-2 over a 1-week period (May 1-7, 2020) using a combined oropharyngeal/nares swab irrespective of whether or not they were identified as "at-risk."

Measurements

Baseline characteristics of patients were acquired using electronic records. In addition to the "at-risk" questionnaire, patients answered "yes" or "no" to any of the following symptoms at the time of the swab (sneeze, fatigue, myalgia, nausea/vomiting, diarrhea, malaise, abdominal pain, loss of taste, and loss of smell).

Results

Of the 334 patients receiving dialysis at the time of the study, 133 resided in areas with evidence of community transmission and 104 consented for the study. No patients met our regional criteria for being "at-risk" and no patients reported cough, sore throat or fever at the time of swab. Many other symptoms were noted, including sneezing (24%), fatigue (16%), myalgias (11%), nausea/vomiting (11%), loss of taste (4%), and loss of smell (4%). Overall, 100% of swabs performed for this study were negative for SARS-CoV-2.

Limitations

Single-center study, and the daily new case rate was exceedingly low (4-14) at the time of the study, emphasizing that the findings are not generalizable to areas of higher prevalence of SARS-CoV-2.

Conclusions

In this study of hemodialysis patients residing in areas with community spread who otherwise did not meet symptom criteria for being "at-risk," we did not identify any individual who tested positive for SARS-CoV-2. Future studies are needed to examine the utility of routine testing for COVID-19 (outside of those who are "at-risk") in areas of higher disease prevalence.

Trial Registration

Not applicable as this is not a clinical trial.

A Provincial Survey of the Contemporary Management of Autosomal Dominant Polycystic Kidney Disease

Background:

Recent years have witnessed an encouraging expansion of knowledge and management tools in the care of patients with autosomal dominant polycystic kidney disease (ADPKD), including measurement of total kidney volume as a biomarker of disease progression, stringent blood pressure targets to slow cyst growth, and targeted treatments such as tolvaptan.

Objectives:

We sought to evaluate clinicians’ familiarity with, and usage of, novel evidence-based management tools for ADPKD.

Design:

On-line survey.

Setting:

British Columbia, Canada.

Participants:

Nephrologists in academic and community practice (excluding clinicians who practice exclusively in transplantation).

Measurements:

Participants answered multiple-choice questions in 6 domains: sources of information, self-identified needs for optimal care delivery, prognostication, imaging tests, blood pressure targets, and use of tolvaptan.

Methods:

An online survey was developed and disseminated via email to 65 nephrologists engaged in current clinical practice in British Columbia.

Results:

A total of 29 nephrologists (45%) completed the questionnaire. The most popular source of information was the primary literature (83% of respondents). While 86% of respondents reported assessing the risk of disease progression before the onset of kidney function decline, most were using traditional metrics such as blood pressure and proteinuria rather than validated prediction tools such as the Mayo Classification. Although 90% of respondents obtained additional imaging after diagnosis in some or all of their ADPKD patients, only 1 in 5 reported being confident in their ability to interpret kidney size. The recommended blood pressure (BP) target of <110/75 mmHg was sought by 17% of respondents. All respondents reported being familiar with the literature regarding tolvaptan; however, only half were confident in their ability to identify suitable patients for treatment. The top 3 needs identified by clinicians were better access to medications (69%), clear management protocols (66%), and easier access to imaging tests (59%).

Limitations:

Funding mechanisms for tolvaptan can vary; therefore, clinicians’ experience with the drug may not be generalizable. Although the response rate was acceptable, the survey is nonetheless subject to responder bias.

Conclusion:

This survey indicates that there is substantial variability in the usage of, and familiarity with, evidence-based ADPKD management tools among contemporary nephrologists, contributing to incomplete translation of evidence into clinical practice. Providing greater access to tolvaptan or imaging tests is unlikely to improve patient care without enhancing knowledge translation and education.

Trial Registration:

Not applicable as this was a survey.

P0350THE DURATION OF PROTEINURIA REMISSION AND CLINICAL OUTCOMES IN IGA NEPHROPATHY

Background and Aims

A relative reduction in proteinuria has been proposed as a surrogate outcome for therapeutic trials in IgA nephropathy. It is currently unknown how long a reduction in proteinuria needs to be maintained in order to mitigate the long-term risk of disease progression. To address this knowledge gap we sought to quantify the association between duration of proteinuria remission and the risk of disease progression in IgA nephropathy.

Method

In this retrospective multi-ethnic international cohort of adult patients with biopsy-proven IgA nephropathy, we defined proteinuria remission based on three criteria: (i) peak proteinuria on/after biopsy ≥1g/day; (ii) an absolute reduction in proteinuria to &lt;1g/day; (iii) a ≥25% reduction in proteinuria from the peak value. The exposure of interest was the total duration of first remission, treated as a time-varying covariate using longitudinal proteinuria measurements. The primary outcome was the occurrence of end-stage kidney disease or a sustained 50% reduction in estimated glomerular filtration rate (eGFR). The association between duration of remission and the primary outcome was visualized using restricted cubic splines, and quantified using extended Cox proportional hazards regression models.

Results

A total of 1864 patients met criteria for remission, which occurred a median of 8.3 months after biopsy (IQR 3.6-22). They had a median age of 36.8 (IQR 29.4-46.6) years and a median eGFR of 78 (IQR 55-104) mL/min/1.73m2. Median proteinuria was 1.54 (IQR 1.09-2.4) g/day at the time of biopsy and 0.55 (IQR 0.33-0.76) g/day at the time of entering remission. During a median follow-up of 3.9 years, 274 patients (14.7%) experienced the primary outcome. The relationship between duration of proteinuria remission and the primary outcome was non-linear (Figure). Each 3 months in sustained remission up to 51 months was associated with an additional 9% reduction in the risk of disease progression (hazard ratio 0.91, 95% confidence interval 0.89-0.93). In contrast, each additional 3 months in remission beyond 51 months was associated with a smaller non-significant risk reduction (hazard ratio 0.99, 95% confidence interval 0.96-1.03). These finding were robust to multivariable adjustment and were consistent across subgroups based on the MEST histology score, and whether or not the remission occurred while on renin-angiotensin-aldosterone-system blockade or after immunosuppression treatment. Results were similar when relapse was defined as either a 50% or 100% increase in proteinuria from the nadir value after remission to an absolute value of ≥1g/day.

Conclusion

We observed a strong non-linear dose-response relationship between the duration of proteinuria remission and the risk of disease progression in patients with IgA nephropathy. The ability to quantitate the renal survival benefit related to the duration of remission is an important advance for patients and their physicians. Rather than there being a minimum duration of proteinuria remission in IgA nephropathy, our results demonstrate that even short durations in remission, or small increases in remission duration, are both associated with significant reductions in the risk of disease progression. For future therapeutic trials in IgA nephropathy using proteinuria as a surrogate outcome, our findings illustrate the need to consider the duration of proteinuria reduction, in addition to the magnitude of proteinuria reduction, when evaluating the anticipated treatment effect on long-term clinical endpoints.

Improving treatment decisions using personalized risk assessment from the International IgA Nephropathy Prediction Tool

Immunosuppression in IgA nephropathy (IgAN) should be reserved for patients at high-risk of disease progression, which KDIGO guidelines determine based solely on proteinuria 1g or more/day. To investigate if treatment decisions can be more accurately accomplished using individualized risk from the International IgAN Prediction Tool, we simulated allocation of a hypothetical immunosuppression therapy in an international cohort of adults with IgAN. Two decision rules for treatment were applied based on proteinuria of 1g or more/day or predicted risk from the Prediction Tool above a threshold probability. An appropriate decision was defined as immunosuppression allocated to patients experiencing the primary outcome (50% decline in eGFR or ESKD) and withheld otherwise. The net benefit and net reduction in treatment are the proportion of patients appropriately allocated to receive or withhold immunosuppression, adjusted for the harm from inappropriate decisions, calculated for all threshold probabilities from 0-100%. Of 3299 patients followed for 5.1 years, 522 (15.8%) experienced the primary outcome. Treatment allocation based solely on proteinuria of 1g or more/day had a negative net benefit (was harmful) because immunosuppression was increasingly allocated to patients without progressive disease. Compared to using proteinuria, treatment allocation using the Prediction Tool had a larger net benefit up to 23.4% (95% confidence interval 21.5-25.2%) and a larger net reduction in treatment up to 35.1% (32.3-37.8%). Thus, allocation of immunosuppression to high-risk patients with IgAN can be substantially improved using the Prediction Tool compared to using proteinuria.

Socioeconomic Position and Incidence of Glomerular Diseases

BACKGROUND AND OBJECTIVES

Social deprivation is a recognized risk factor for undifferentiated CKD; however, its association with glomerular disease is less well understood. We sought to investigate the relationship between socioeconomic position and the population-level incidence of biopsy-proven glomerular diseases.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this retrospective cohort study, a provincial kidney pathology database (2000-2012) was used to capture all incident cases of membranous nephropathy (n=392), IgA nephropathy (n=818), FSGS (n=375), ANCA-related GN (ANCA-GN, n=387), and lupus nephritis (n=389) in British Columbia, Canada. Quintiles of area-level household income were used as a proxy for socioeconomic position, accounting for regional differences in living costs. Incidence rates were direct standardized to the provincial population using census data for age and sex and were used to generate standardized rate ratios. For lupus nephritis, age standardization was performed separately in men and women.

RESULTS

A graded increase in standardized incidence with lower income was observed for lupus nephritis (P<0.001 for trend in both sexes) and ANCA-GN (P=0.04 for trend). For example, compared with the highest quintile, the lowest income quintile had a standardized rate ratio of 1.7 (95% confidence interval, 1.19 to 2.42) in women with lupus nephritis and a standardized rate ratio of 1.5 (95% confidence interval, 1.09 to 2.06) in ANCA-GN. The association between income and FSGS was less consistent, in that only the lowest income quintile was associated with a higher incidence of disease (standardized rate ratio, 1.55; 95% confidence interval, 1.13 to 2.13). No significant associations were demonstrated for IgA nephropathy or membranous nephropathy.

CONCLUSIONS

Using population-level data and a centralized pathology database, we observed an inverse association between socioeconomic position and the standardized incidence of lupus nephritis and ANCA-GN.

Mortality in Relation to Changes in a Healthy Aging Index: The Health, Aging, and Body Composition Study

BACKGROUND

Baseline scores on a Healthy Aging Index (HAI), including five key physiologic domains, strongly predict health outcomes. This study aimed to characterize 9-year changes in a HAI and explore their relationship to subsequent mortality.

METHODS

Data are from the Health, Aging, and Body Composition study of well-functioning adults aged 70-79 years. A HAI, which ranges from 0 to 10, was constructed at years 1 and 10 of the study including systolic blood pressure, forced expiratory volume, digit symbol substitution test, cystatin C, and fasting glucose. The relationships between the HAI at years 1 and 10 and the change between years and subsequent mortality until year 17 were estimated from Cox proportional hazards models.

RESULTS

Two thousand two hundred sixty-four participants had complete data on a HAI at year 1, of these 1,122 had complete data at year 10. HAI scores tended to increase (i.e. get worse) over 9-year follow-up, from (mean [SD]) 4.3 (2.1) to 5.7 (2.1); mean within-person change 1.5 (1.6). After multivariable adjustment, HAI score was related to mortality from year 1 (hazard ratio [95% confidence interval] = 1.17 [1.13-1.21] per unit) and year 10 (1.20 [1.14-1.27] per unit). The change between years was also related to mortality (1.08 [1.02-1.15] per unit change).

CONCLUSIONS

HAI scores tended to increase with advancing age and stratified mortality rates among participants remaining at year 10. The HAI may prove useful to understand changes in health with aging.

P05.05 Safety and feasibility of temporary blood-brain barrier disruption with the SonoCloud-1/3 implantable ultrasound device in recurrent glioblastoma

BACKGROUND

The blood-brain barrier (BBB) limits penetration of drug therapies to the brain and may account for the limited effectiveness of chemotherapies in patients with primary brain cancer. An implantable ultrasound (US) device, SonoCloud, was developed to temporarily disrupt the BBB in patients with recurrent glioblastoma (rGBM) prior to carboplatin chemotherapy administration to enhance brain drug concentrations. BBB disruption was investigated with a single emitter device, SonoCloud-1 (SC1) and a three-emitter device, SonoCloud-3 (SC3) in a safety and feasibility study in rGBM patients at the Hôpitaux Universitaires La Pitié Salpêtrière in Paris, France (NCT02253212).

MATERIAL AND METHODS

The SC1 implant consisted of a 1 MHz, 10-mm diameter ultrasound transducer encapsulated in a biocompatible housing while the SC3 consisted of (3) separate SC1 emitters implanted in a triangular pattern to disrupt the BBB over a 3x larger volume. Patients were implanted with the SonoCloud device during tumor debulking or in a dedicated surgical procedure. The devices were activated monthly by connecting the device to an external generator via a transdermal needle. Intravenous injection of SonoVue® microbubbles was performed with device activation to temporarily disrupt the BBB. Magnetic resonance imaging (MRI) was performed after sonications with gadolinium contrast to verify BBB disruption followed by carboplatin infusion at AUC4-6. Patients received treatments until disease progression.

RESULTS

Between 2014 and 2016, 21 patients were registered for the study and implanted with the SC1; 19 patients received at least one sonication. Six additional patients were implanted and received sonications with the SC3. A total of 89 US sessions were performed to disrupt the BBB - 65 with the SC1 and 24 with the SC3. Treatment-related adverse events observed were transient and manageable. No carboplatin-related neurotoxicity was observed. SC1 patients with no or poor BBB disruption (n=8) visible on MRI had a median progression-free survival (PFS) of 2.73 months, and a median overall survival (OS) of 8.64 months. SC1 patients with clear BBB disruption (n=11) had a median PFS of 4.11 months, and a median OS of 12.94 months. The SC3 device was as well-tolerated as the SC1 device, with SC3 patients receiving between 1–12 monthly sonications.

CONCLUSION

These results provide the first safety data on the effects of disrupting the BBB in rGBM patients prior to carboplatin chemotherapy using an implantable low intensity pulsed ultrasound device on enlarged areas of brain. This study has now been completed. A new safety study with a larger device, SonoCloud-9, that covers the tumor and surrounding infiltrative regions, has started in France in early 2019 (NCT03744026). Work supported by CarThera and APHP.

Glomerular Filtration Rate-Specific Cutoffs Can Refine the Prognostic Value of Circulating Cardiac Biomarkers in Advanced Chronic Kidney Disease

BACKGROUND

Using standard cutoffs derived from healthy adults, high-sensitivity cardiac troponin T (hs-cTnT) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) are frequently elevated in patients with reduced glomerular filtration rate (GFR), with unclear implications. We sought to compare GFR-specific cutoffs of each biomarker with standard cutoffs for discrimination of cardiovascular risk in asymptomatic patients with chronic kidney disease.

METHODS

We investigated a prospective cohort of 1956 participants with median GFR of 27 mL/min/1.73 m². Cox proportional hazards models were used to examine the association between each biomarker and first adjudicated cardiovascular event (unstable angina, myocardial infarction, heart failure, stroke, cardiovascular death). We used an outcome-based approach to identify optimal risk-based cutoffs for each biomarker within GFR strata (< 20, 20-29, 30-44 mL/min/1.73 m²). We evaluated the added prognostic value of each biomarker to a multivariable base model, comparing GFR-specific with standard cutoffs.

RESULTS

Hs-cTnT and NT-proBNP were elevated in 76% and 82% of participants, respectively. A total of 401 events were recorded during 6772 person-years at risk. Both biomarkers were independent predictors of cardiovascular events. Optimal cutoffs for each biomarker were higher than standard thresholds, being highest at GFR values < 20 mL/min/1.73 m². Addition of hs-cTnT to the base model using GFR-specific cutoffs significantly improved reclassification for events (52%) and nonevents (21%). Similar findings were observed for NT-proBNP. In contrast, use of standard cutoffs failed to reclassify patients who had no event as lower risk.

CONCLUSIONS

Among asymptomatic patients with advanced chronic kidney disease, optimal cutoffs for hs-cTnT and NT-proBNP differed according to GFR level and outperformed standard cutoffs for discrimination of cardiovascular risk.

GFR-Specific versus GFR-Agnostic Cutoffs for Parathyroid Hormone and Fibroblast Growth Factor-23 in Advanced Chronic Kidney Disease

BACKGROUND

In the majority of patients with advanced chronic kidney disease (CKD), values of parathyroid hormone (PTH1-84) and fibroblast growth factor 23 (FGF-23) exceed the normal reference range, potentially as an appropriate adaptation to reduced glomerular filtration rate (GFR). We tested whether GFR-specific cutoffs for PTH1-84 and FGF-23 could better identify patients with inappropriately high PTH1-84 and FGF-23 for their degree of CKD and thereby improve prognostication of clinical outcomes compared to a uniform threshold.

METHODS

Prospective pan-Canadian cohort of 1,812 patients with mean estimated GFR (eGFR) 28.9 mL/min/1.73 m2 followed for a median of 52 months. Repeated log-rank tests were used to identify optimal cutoffs for PTH1-84 and FGF-23 within eGFR strata (<20, 20-29 and ≥30 mL/min/1.73 m2) that maximally differentiated high- and low-risk populations for (1) cardiovascular (CV) events (fatal or nonfatal myocardial infarction, coronary revascularization, stroke, heart failure) and (2) renal events (initiation of chronic renal replacement therapy). In multivariable models, we examined the association between -GFR-specific cutoffs and outcomes and compared their added prognostic value to existing uniform thresholds.

RESULTS

Risk-based cutoffs for PTH1-84 and FGF-23 increased in a graded fashion with decreasing eGFR. Among patients with eGFR <20 mL/min/1.73 m2, CV risk-based cutoffs for PTH1-84 and FGF-23 were 3.4 and 5.5 times the upper limit of normal, respectively, and reclassified 31.9 and 35.1% of patients when added to a multivariable base model for CV events. In contrast, the addition of PTH1-84 and FGF-23 to the base model using uniform cutoffs failed to reclassify such patients. Similar findings were demonstrated for renal outcomes.

CONCLUSION

GFR-specific risk-based cutoffs for PTH1-84 and FGF-23 may facilitate more meaningful risk stratification in advanced CKD than current GFR-agnostic reference ranges derived from healthy adults. This may be most applicable in those with severely reduced GFR.

Data linkage in medical science using the resource description framework: the AVERT model

There is an ongoing challenge as to how best manage and understand ‘big data’ in precision medicine settings. This paper describes the potential for a Linked Data approach, using a Resource Description Framework (RDF) model, to combine multiple datasets with temporal and spatial elements of varying dimensionality. This “AVERT model” provides a framework for converting multiple standalone files of various formats, from both clinical and environmental settings, into a single data source. This data source can thereafter be queried effectively, shared with outside parties, more easily understood by multiple stakeholders using standardized vocabularies, incorporating provenance metadata and supporting temporo-spatial reasoning. The approach has further advantages in terms of data sharing, security and subsequent analysis. We use a case study relating to anti-Glomerular Basement Membrane (GBM) disease, a rare autoimmune condition, to illustrate a technical proof of concept for the AVERT model.