Non-linear relationships in clinical research.

True linear relationships are rare in clinical data. Despite this, linearity is often assumed during analyses, leading to potentially biased estimates and inaccurate conclusions. In this introductory paper, we aim to first describe - in a non-mathematical manner - how to identify non-linear relationships. Various methods are then discussed that can be applied to deal with non-linearity, including transformations, polynomials, splines, and Generalized Additive Models (GAMs), along with their strengths and weaknesses. Finally, we illustrate the use of these methods with a practical example from nephrology, providing guidance on how to report the results from non-linear relationships.

When impact trials are not feasible: alternatives to study the impact of prediction models on clinical practice.

Patients with kidney disease have an uncertain future with prognosis varying greatly per patient. To get a better idea of what the future holds and tailor interventions to the individual patient, prediction models can be of great value. Before a prediction model can be applied in practice, its performance should be measured in target populations of interest (i.e., external validation) and whether it helps improve clinical practice (i.e., whether it impacts clinical practice) should be determined. The impact would ideally be determined using an impact trial, but such a trial is often not feasible, and the impact of prediction models is therefore rarely assessed. As a result, prediction models that may not be so impactful may end up in clinical practice and impactful models may not be implemented due to a lack of impact studies. Ultimately, many prediction models end up never being implemented, resulting in much research waste. To allow researchers to get an indication of a prediction model's impact on clinical practice, alternative methods to assess a prediction model's impact are important. In this paper, we discuss several alternatives, including interviews, case-based surveys, decision comparisons, outcome modelling, before-after analyses, and decision curve analyses. We discuss the general idea behind these approaches, including what information can be gathered from such studies and important pitfalls. Lastly, we provide examples of the different alternatives.

Adult outcomes of childhood kidney replacement therapy in Europe from 2008 to 2019: an ERA Registry study.

BACKGROUND AND HYPOTHESIS: Young adults starting kidney replacement therapy (KRT) during childhood and reaching their 18th birthday (i.e. adult survivors of childhood KRT) form a challenging population of interest to nephrologists treating adults, as during this period there will be a transition to adult renal centres. Nonetheless, few studies have focused on the epidemiology of KRT in this group. We aimed to provide an update on these patients' characteristics, treatment history, graft and patient survival, to report their 5-year prognosis, and expected remaining lifetime. METHODS: Data on KRT patients reaching their 18th birthday in 2008-2019 were collected from 21 European countries/regions providing individual patient data to the European Renal Association (ERA) Registry. Patient characteristics and treatment trajectories were examined before and after turning 18 years. Kaplan-Meier and Cox proportional hazards regression were used for patient and graft survival analyses. RESULTS: In total, 2944 patients were included. The proportion of adult survivors initiating KRT at a very young age (0-4 years), and undergoing pre-emptive kidney transplantation increased. Unadjusted 5-year patient survival was 96.9% (95% CI: 96.2-97.5). Dialysis patients had a higher risk of death than kidney transplant recipients (adjusted hazard ratio 5.44 (95% CI: 3.34-8.86)). Between ages 18 and 23 years, about 21% of the adult survivors lost their kidney transplant and 34% of the dialysis patients continued this treatment. Compared with the general population, life expectancy for eighteen-year-old kidney transplant and dialysis patients was 17 and 40 years shorter, respectively. CONCLUSION: Life expectancy of 18-year-old kidney transplant recipients was lower compared with the general population. Yet, having a functioning kidney graft at age 18 years resulted in better outcomes than being on dialysis. Nevertheless, between ages 18 and 23 years, about one-fifth of the kidney grafts failed and one-third of the patients remained on dialysis.

The safety of a low protein diet in older adults with advanced chronic kidney disease.

BACKGROUND: A low protein diet (LPD) is recommended to patients with advanced chronic kidney disease (CKD), whereas geriatric guidelines recommend a higher amount of protein. The aim of this study was to evaluate the safety of LPD treatment in older adults with advanced CKD. METHODS: The EQUAL study is a prospective, observational study, including patients ≥65 years, incident estimated glomerular filtration rate <20 ml/min/1.73m², in six European countries with follow-up up till six years. Nutritional status was assessed by 7-point subjective global assessment (SGA) every 3-6 months. Prescribed diet (gram protein/kilogram/bodyweight) was recorded on every study visit; measured protein intake was available in three countries. Time to death and decline in nutritional status (SGA decrease by ≥2 points) were analysed using marginal structural models with dynamic inverse probability of treatment and censoring weights. RESULTS: Out of 1738 adults (631 prescribed LPD at any point during follow-up) there were 1319 with repeated SGA measurements of which 267 (20%) declined in SGA ≥ 2 points and 565 (32.5%) died. There was no difference in survival or decline in nutritional status for patients prescribed LPD ≤0.8 g/kg ideal bodyweight (Odds Ratio (OR) for mortality 1.15 (95% Confidence interval (CI) 0.86-1.55) and OR for decline in SGA 1.11 (95% CI 0.74-1.66) in the adjusted models. In patients prescribed LPD <0.6 g/kg ideal bodyweight, the results were similar. There was a significant interaction with LPD and higher age >75 years, lower SGA, and higher comorbidity burden for both mortality and nutritional status decline. CONCLUSIONS: In older adults with CKD approaching end-stage kidney disease, a traditional LPD prescribed and monitored according to routine clinical practice in Europe appears to be safe.

International comparison and time trends of first kidney transplant recipient characteristics across Europe: an ERA Registry study.

BACKGROUND: The aim of this study was to provide an overview of age, sex and primary renal disease (PRD) distribution among first kidney transplant recipients across Europe. METHOD: The European Renal Association (ERA) Registry database was used to obtain data on patients aged 20 years or older receiving their first kidney transplant between 2010 and 2019 from 12 European countries. The numbers and percentages of recipients in each age, sex and PRD group were calculated by country, donor type and year. RESULTS: In total, 99 543 adults received a first kidney transplant. Overall, 23% of the recipients were 65 years or older, 36% were female, and 21% had glomerulonephritis and 15% diabetes mellitus as PRD. Compared with deceased donor kidney transplant recipients, living donor kidney transplant recipients were less often 65 years or older (13% versus 26%), more often had glomerulonephritis (25% versus 20%) and less often diabetes mellitus (8% versus 17%) as PRD. We found large international differences, which were most prominent for age and PRD and less prominent for sex. Over time, the largest change in recipient characteristics was observed for the percentage of recipients aged 65 years or older, increasing from 18% in 2010 to 28% in 2019 for all countries combined with a similar trend in most countries. CONCLUSION: We observed large differences for age and PRD distribution between recipients of living and deceased donor kidneys and between European countries. Over time, the percentage of older first kidney transplant recipients increased.

Time trends in preemptive kidney transplantation in Europe: an era registry study.

BACKGROUND: Preemptive kidney transplantation has better outcomes when compared to transplantation after dialysis. We aimed to examine trends in preemptive kidney transplantation between 2000 and 2019 in Europe and to provide an overview of associated policies, barriers and initiatives. METHODS: Adult patients from 12 European countries who received a preemptive kidney transplant were included. The representatives of the registries providing these data were questioned on the policies, barriers and initiatives around preemptive kidney transplantation. RESULTS: Between 2000 and 2019, 20 251 adults underwent preemptive kidney transplantation (11 169 from living donors, 8937 from deceased donors). The proportion of first kidney transplantations that were preemptive more than doubled from 7% in 2000 to 18% in 2019, reflecting a similar relative increase for living donor kidney recipients (from 21% to 43%) and deceased donor kidney recipients (from 4% to 11%). Large international differences were found. The increase in preemptive kidney transplantation was observed across all age, sex and primary renal disease groups. Countries had similar criteria for preemptive waitlisting. Barriers mentioned included donor shortage, late referral to the transplant center and long donor or recipient work-up. Suggested initiatives included raising awareness on the possibility of preemptive kidney transplantation, earlier start and shorter work-up time for recipient and living donor. CONCLUSIONS: Over the last two decades the proportion of patients receiving a first kidney transplant preemptively has more than doubled, reflecting a similar relative increase for living and deceased donor kidney recipients.

Changes in the epidemiology of kidney replacement therapy across Europe in 2020 - the first year of the COVID-19 pandemic: an ERA Registry study.

BACKGROUND: In 2020, the COVID-19 pandemic caused disruptions in kidney replacement therapy (KRT) services worldwide. The aim of this study was to assess the effect of the COVID-19 pandemic in 2020 on the incidence of KRT, kidney transplantation activity, mortality and prevalence of KRT across Europe. METHODS: Patients receiving KRT were included from 17 countries providing data to the European Renal Association Registry. The epidemiology of KRT in 2020 was compared with average data from the period 2017-2019. Also changes occurring during the first and second wave of the pandemic were explored. RESULTS: The incidence of KRT was 6.2% lower in 2020 compared with 2017-2019, with the lowest point (-22.7%) during the first wave in April. The decrease varied across countries, was smaller in males (-5.2%) than in females (-8.2%), and was moderate for peritoneal dialysis (-3.7%) and haemodialysis (-5.4%), but substantial for pre-emptive kidney transplantation (-23.6%). The kidney transplantation rate decreased by 22.5%, reaching a nadir of -80.1% during the first wave, and most for living donor kidney transplants (-30.5%). While in most countries the kidney transplantation rate decreased, in the Nordic/Baltic countries and Greece there was no clear decline. In dialysis patients, mortality increased by 11.4%, and was highest in those aged 65-74 years (16.1%), in those with diabetes as primary renal disease (15.1%), and in those on haemodialysis (12.4%). In transplant recipients, the mortality was 25.8% higher, but there were no subgroups that stood out. In contrast to the rising prevalence of KRT observed over the past decades across Europe, the prevalence at the end of 2020 (N=317787) resembled that of 2019 (N=317077). CONCLUSION: The COVID-19 pandemic has had a substantial impact on the incidence of KRT, kidney transplant activity, mortality of KRT, and prevalence of KRT in Europe with variations across countries.

Incidence and outcomes of kidney replacement therapy for end-stage kidney disease due to primary glomerular disease in Europe: findings from the ERA Registry.

BACKGROUND: Primary glomerular disease (PGD) is a major cause of end-stage kidney disease (ESKD) leading to kidney replacement therapy (KRT). We aimed to describe incidence (trends) in individuals starting KRT for ESKD due to PGD and to examine their survival and causes of death. METHODS: We used data from the European Renal Association (ERA) Registry on 69 854 patients who started KRT for ESKD due to PGD between 2000 and 2019. ERA primary renal disease codes were used to define six PGD subgroups. We examined age and sex standardized incidence, trend of the incidence and survival. RESULTS: The standardized incidence of KRT for ESKD due to PGD was 16.6 per million population (pmp), ranging from 8.6 pmp in Serbia to 20.0 pmp in France. Immunoglobulin A nephropathy (IgAN) and focal segmental glomerulosclerosis (FSGS) had the highest incidences, of 4.6 pmp and 2.6 pmp, respectively. Histologically non-examined PGDs represented over 50% of cases in Serbia, Bosnia and Herzegovina, and Romania and were also common in Greece, Estonia, Belgium and Sweden. The incidence declined from 18.6 pmp in 2000 to 14.5 pmp in 2013, after which it stabilized. All PGD subgroups had 5-year survival probabilities above 50%, with crescentic glomerulonephritis having the highest risk of death [adjusted hazard ratio 1.8 (95% confidence interval 1.6-1.9)] compared with IgAN. Cardiovascular disease was the most common cause of death (33.9%). CONCLUSION: The incidence of KRT for ESKD due to PGD showed large differences between countries and was highest and increasing for IgAN and FSGS. Lack of kidney biopsy facilities in some countries may have affected accurate assignment of the cause of ESKD. The recognition of the incidence and outcomes of KRT among different PGD subgroups may contribute to a more individualized patient care approach.

A comparison of the epidemiology of kidney replacement therapy between Europe and the United States: 2021 data of the ERA Registry and the USRDS.

BACKGROUND: This paper compares the most recent data on the incidence and prevalence of kidney replacement therapy (KRT), kidney transplantation rates, and mortality on KRT from Europe to those from the United States (US), including comparisons of treatment modalities (haemodialysis (HD), peritoneal dialysis (PD), and kidney transplantation (KTx)). METHODS: Data were derived from the annual reports of the European Renal Association (ERA) Registry and the United States Renal Data System (USRDS). The European data include information from national and regional renal registries providing the ERA Registry with individual patient data. Additional analyses were performed to present results for all participating European countries together. RESULTS: In 2021, the KRT incidence in the US (409.7 per million population (pmp)) was almost 3-fold higher than in Europe (144.4 pmp). Despite the substantial difference in KRT incidence, approximately the same proportion of patients initiated HD (Europe: 82%, US: 84%), PD (14%; 13%, respectively), or underwent pre-emptive KTx (4%; 3%, respectively). The KRT prevalence in the US (2436.1 pmp) was 2-fold higher than in Europe (1187.8 pmp). Within Europe, approximately half of all prevalent patients were living with a functioning graft (47%), while in the US, this was one third (32%). The number of kidney transplantations performed was almost twice as high in the US (77.0 pmp) compared to Europe (41.6 pmp). The mortality of patients receiving KRT was 1.6-fold higher in the US (157.3 per 1000 patient years) compared to Europe (98.7 per 1000 patient years). CONCLUSIONS: The US had a much higher KRT incidence, prevalence, and mortality compared to Europe, and despite a higher kidney transplantation rate, a lower proportion of prevalent patients with a functioning graft.

Defining measures of kidney function in observational studies using routine health care data: methodological and reporting considerations.

The availability of electronic health records and access to a large number of routine measurements of serum creatinine and urinary albumin enhance the possibilities for epidemiologic research in kidney disease. However, the frequency of health care use and laboratory testing is determined by health status and indication, imposing certain challenges when identifying patients with kidney injury or disease, when using markers of kidney function as covariates, or when evaluating kidney outcomes. Depending on the specific research question, this may influence the interpretation, generalizability, and/or validity of study results. This review illustrates the heterogeneity of working definitions of kidney disease in the scientific literature and discusses advantages and limitations of the most commonly used approaches using 3 examples. We summarize ways to identify and overcome possible biases and conclude by proposing a framework for reporting definitions of exposures and outcomes in studies of kidney disease using routinely collected health care data.

Serum Potassium and Risk of Death or Kidney Replacement Therapy in Older People With CKD Stages 4-5: Eight-Year Follow-up.

RATIONALE & OBJECTIVE: Hypokalemia may accelerate kidney function decline. Both hypo- and hyperkalemia can cause sudden cardiac death. However, little is known about the relationship between serum potassium and death or the occurrence of kidney failure requiring replacement therapy (KRT). We investigated this relationship in older people with chronic kidney disease (CKD) stage 4-5. STUDY DESIGN: Prospective observational cohort study. SETTING & PARTICIPANTS: We followed 1,714 patients (≥65 years old) from the European Quality (EQUAL) study for 8 years from their first estimated glomerular filtration rate (eGFR)<20mL/min/1.73m2 measurement. EXPOSURE: Serum potassium was measured every 3 to 6 months and categorized as≤3.5,>3.5-≤4.0,>4.0-≤4.5,>4.5-≤5.0 (reference),>5.0-≤5.5, >5.5-≤6.0, and>6.0mmol/L. OUTCOME: The combined outcome death before KRT or start of KRT. ANALYTICAL APPROACH: The association between categorical and continuous time-varying potassium and death or KRT start was examined using Cox proportional hazards and restricted cubic spline analyses, adjusted for age, sex, diabetes, cardiovascular disease, renin-angiotensin-aldosterone system (RAAS) inhibition, eGFR, and subjective global assessment (SGA). RESULTS: At baseline, 66% of participants were men, 42% had diabetes, 47% cardiovascular disease, and 54% used RAAS inhibitors. Their mean age was 76±7 (SD) years, mean eGFR was 17±5 (SD) mL/min/1.73m2, and mean SGA was 6.0±1.0 (SD). Over 8 years, 414 (24%) died before starting KRT, and 595 (35%) started KRT. Adjusted hazard ratios for death or KRT according to the potassium categories were 1.6 (95% CI, 1.1-2.3), 1.4 (95% CI, 1.1-1.7), 1.1 (95% CI, 1.0-1.4), 1 (reference), 1.1 (95% CI, 0.9-1.4), 1.8 (95% CI, 1.4-2.3), and 2.2 (95% CI, 1.5-3.3). Hazard ratios were lowest at a potassium of about 4.9mmol/L. LIMITATIONS: Shorter intervals between potassium measurements would have allowed for more precise estimations. CONCLUSIONS: We observed a U-shaped relationship between serum potassium and death or KRT start among patients with incident CKD 4-5, with a nadir risk at a potassium level of 4.9mmol/L. These findings underscore the potential importance of preventing both high and low potassium in patients with CKD 4-5. PLAIN-LANGUAGE SUMMARY: Abnormal potassium blood levels may increase the risk of death or kidney function decline, especially in older people with chronic kidney disease (CKD). We studied 1,714 patients aged≥65 years with advanced CKD from the European Quality (EQUAL) study and followed them for 8 years. We found that both low and high levels of potassium were associated with an increased risk of death or start of kidney replacement therapy, with the lowest risk observed at a potassium level of 4.9 mmol/L. In patients with CKD, the focus is often on preventing high blood potassium. However, this relatively high optimum potassium level stresses the potential importance of also preventing low potassium levels in older patients with advanced CKD.

Factors influencing kidney transplantation rates: a study from the ERA Registry.

BACKGROUND: Large international differences exist in kidney transplantation (KT) rates. We aimed to investigate which factors may explain the total, deceased donor and living donor KT rates over the last decade. METHODS: KT experts from 39 European countries completed the Kidney Transplantation Rate Survey on measures and barriers and their potential effect on the KT rate in their country. In the analyses, countries were divided into low, middle and high KT rate countries based on the KT rate at the start of study period in 2010. RESULTS: Experts from low KT rate countries reported more frequently that they had taken measures regarding staff, equipment and facilities to increase the total KT rate compared with middle and high KT rate countries. For donor type-specific KT, the largest international differences in measures taken were reported for deceased donor KT, with middle and high KT rate countries taking more measures, such as the use of expanded criteria donor kidneys, the presence of transplantation coordinators and (inter)national exchange of donor kidneys. Once a measure was taken, experts' opinion on its success was similar across the low, middle and high KT rate countries. Experts from low KT rate countries more often reported potential barriers, such as patients' lack of knowledge and distrust in the healthcare system. CONCLUSIONS: Particularly in low KT rate countries, the KT rate might be stimulated by optimizing staff, equipment and facilities. In addition, all countries may benefit from measures specific to deceased and living donors.

Clinical and patient-reported trajectories at end-of-life in older patients with advanced CKD.

BACKGROUND: We explore longitudinal trajectories of clinical indicators, patient-reported outcomes, and hospitalizations, in the years preceding death in a population of older patients with advanced chronic kidney disease (CKD). METHODS: The EQUAL study is a European observational prospective cohort study with an incident eGFR <20 ml/min per 1.73 m2 and ≥65 years of age. The evolution of each clinical indicator was explored using generalized additive models during the 4 years preceding death. RESULTS: We included 661 decedents with a median time to death of 2.0 years (IQR 0.9-3.2). During the years preceding death, eGFR, Subjective Global Assessment score, and blood pressure declined, with accelerations seen at 6 months preceding death. Serum hemoglobin, hematocrit, cholesterol, calcium, albumin, and sodium values declined slowly during follow-up, with accelerations observed between 6 and 12 months preceding death. Physical and mental quality of life declined linearly throughout follow-up. The number of reported symptoms was stable up to 2 years prior to death, with an acceleration observed at 1 year prior to death. The rate of hospitalization was stable at around one hospitalization per person year, increasing exponentially at 6 months preceding death. CONCLUSIONS: We identified clinically relevant physiological accelerations in patient trajectories that began ∼6 to 12 months prior to death, which are likely multifactorial in nature, but correlate with a surge in hospitalizations. Further research should focus on how to effectively use this knowledge to inform patient and family expectations, to benefit the planning of (end-of-life) care, and to establish clinical alert systems.

Association between CKD-MBD and mortality in older patients with advanced CKD-results from the EQUAL study.

BACKGROUND: Chronic kidney disease-mineral and bone disorder (CKD-MBD) is a common complication of CKD; it is associated with higher mortality in dialysis patients, while its impact in non-dialysis patients remains mostly unknown. We investigated the associations between parathyroid hormone (PTH), phosphate and calcium (and their interactions), and all-cause, cardiovascular (CV) and non-CV mortality in older non-dialysis patients with advanced CKD. METHODS: We used data from the European Quality study, which includes patients aged ≥65 years with estimated glomerular filtration rate ≤20 mL/min/1.73 m2 from six European countries. Sequentially adjusted Cox models were used to assess the association between baseline and time-dependent CKD-MBD biomarkers and all-cause, CV and non-CV mortality. Effect modification between biomarkers was also assessed. RESULTS: In 1294 patients, the prevalence of CKD-MBD at baseline was 94%. Both PTH [adjusted hazard ratio (aHR) 1.12, 95% confidence interval (CI) 1.03-1.23, P = .01] and phosphate (aHR 1.35, 95% CI 1.00-1.84, P = .05), but not calcium (aHR 1.11, 95% CI 0.57-2.17, P = .76), were associated with all-cause mortality. Calcium was not independently associated with mortality, but modified the effect of phosphate, with the highest mortality risk found in patients with both hypercalcemia and hyperphosphatemia. PTH level was associated with CV mortality, but not with non-CV mortality, whereas phosphate was associated with both CV and non-CV mortality in most models. CONCLUSIONS: CKD-MBD is very common in older non-dialysis patients with advanced CKD. PTH and phosphate are independently associated with all-cause mortality in this population. While PTH level is only associated with CV mortality, phosphate seems to be associated with both CV and non-CV mortality.

Preparing European Nephrology for the next pandemic: lessons from the ERACODA collaboration.

Owing to the vulnerability of patients with chronic kidney disease to infectious diseases, the coronavirus disease 2019 (COVID-19) pandemic has been particularly devastating for the nephrology community. Unfortunately, the possibility of future COVID-19 waves or outbreaks of other infectious diseases with pandemic potential cannot be ruled out. The nephrology community made tremendous efforts to contain the consequences of the COVID-19 pandemic. Despite this, the COVID-19 pandemic has highlighted several shortcomings in our response to the pandemic and has taught us important lessons that can be utilized to improve our preparedness for any future health crises of a similar nature. In this article we draw lessons from the European Renal Association COVID-19 Database (ERACODA) project, a pan-European collaboration initiated in March 2020 to understand the prognosis of COVID-19 in patients on kidney function replacement therapy. We discuss the challenges faced in generating timely and robust evidence for informed management of patients with kidney disease and give recommendations for our preparedness for the next pandemic in Europe. Limited collaboration, the absence of common data architecture and the sub-optimal quality of available data posed challenges in our response to COVID-19. Aligning different research initiatives, strengthening electronic health records, and involving experts in study design and data analysis will be important in our response to the next pandemic. The European Renal Association may take a leading role in aligning research initiatives via its engagement with other scientific societies, national registries, administrators and researchers.

Increasing numbers and improved overall survival of patients on kidney replacement therapy over the last decade in Europe: an ERA Registry study.

BACKGROUND: The aim of this study was to describe the trends in the incidence, prevalence and survival of patients on kidney replacement therapy (KRT) for end-stage kidney disease (ESKD) across Europe from 2008 to 2017. METHODS: Data from renal registries in 9 countries and 16 regions that provided individual patient data to the ERA Registry from 2008 to 2017 were included. These registries cover 34% of the general population in Europe. Crude and standardized incidence and prevalence per million population (pmp) were determined. Trends over time were studied using Joinpoint regression. Survival probabilities were estimated using Kaplan-Meier analysis and hazard ratios (HRs) using Cox regression analysis. RESULTS: The standardized incidence of KRT was stable [annual percentage change (APC): -1.48 (-3.15; 0.21)] from 2008 (146.0 pmp) to 2011 (141.6 pmp), followed by a slight increase [APC: 1.01 (0.43; 1.60)] to 148.0 pmp in 2017, although trends in incidence varied across countries. This increase was primarily due to a rise in the incidence of KRT in men older than 65 years. Moreover, as a cause of kidney failure, diabetes mellitus is increasing. The standardized prevalence increased from 2008 (990.0 pmp) to 2017 (1166.8 pmp) [APC: 1.82 (1.75; 1.89)]. Patient survival on KRT improved in the time period 2011-13 compared with 2008-[adjusted HR: 0.94 (0.93; 0.95)]. CONCLUSION: This study showed an overall increase in the incidence and prevalence of KRT for ESKD as well as an increase in the KRT patient survival over the last decade in Europe.

Trends in kidney transplantation rate across Europe: study from the ERA Registry.

BACKGROUND: The aim of this study was to identify trends in total, deceased donor (DD) and living donor (LD) kidney transplantation (KT) rates in European countries. METHODS: The European Renal Association (ERA) Registry and the Global Observatory on Donation and Transplantation (GODT) databases were used to obtain the number of KTs in individual European countries between 2010 and 2018. General population counts were obtained from Eurostat or the national bureaus of statistics. The KT rate per million population (p.m.p.) and the average annual percentage change (APC) were calculated. RESULTS: The total KT rate in the 40 participating countries increased with 1.9% annually  [95%  confidence  interval  (CI) 1.5, 2.2] from 29.6 p.m.p. in 2010 to 34.7 p.m.p. in 2018, reflecting an increase of 3.4 p.m.p. in the DD-KT rate (from 21.6 p.m.p. to 25.0 p.m.p.; APC 1.9%; 95% CI 1.3, 2.4) and of 1.5 p.m.p. in the LD-KT rate (from 8.1 p.m.p. to 9.6 p.m.p.; APC 1.6%; 95% CI 1.0, 2.3). The trends in KT rate varied widely across European countries. An East-West gradient was observed for DD-KT rate, with Western European countries performing more KTs. In addition, most countries performed fewer LD-KTs. In 2018, Spain had the highest DD-KT rate (64.6 p.m.p.) and Turkey the highest LD-KT rate (37.0 p.m.p.). CONCLUSIONS: The total KT rate increased due to a rise in the KT rate from DDs and to a lesser extent from LDs, with large differences between individual European countries.

Associations of longitudinal height and weight with clinical outcomes in pediatric kidney replacement therapy: results from the ESPN/ERA Registry.

BACKGROUND: Associations between anthropometric measures and patient outcomes in children are inconsistent and mainly based on data at kidney replacement therapy (KRT) initiation. We studied associations of height and body mass index (BMI) with access to kidney transplantation, graft failure, and death during childhood KRT. METHODS: We included patients < 20 years starting KRT in 33 European countries from 1995-2019 with height and weight data recorded to the ESPN/ERA Registry. We defined short stature as height standard deviation scores (SDS) < -1.88 and tall stature as height SDS > 1.88. Underweight, overweight and obesity were calculated using age and sex-specific BMI for height-age criteria. Associations with outcomes were assessed using multivariable Cox models with time-dependent covariates. RESULTS: We included 11,873 patients. Likelihood of transplantation was lower for short (aHR: 0.82, 95% CI: 0.78-0.86), tall (aHR: 0.65, 95% CI: 0.56-0.75), and underweight patients (aHR: 0.79, 95%CI: 0.71-0.87). Compared with normal height, patients with short and tall statures showed higher graft failure risk. All-cause mortality risk was higher in short (aHR: 2.30, 95% CI: 1.92-2.74), but not in tall stature. Underweight (aHR: 1.76, 95% CI: 1.38-2.23) and obese (aHR: 1.49, 95% CI: 1.11-1.99) patients showed higher all-cause mortality risk than normal weight subjects. CONCLUSIONS: Short and tall stature and being underweight were associated with a lower likelihood of receiving a kidney allograft. Mortality risk was higher among pediatric KRT patients with a short stature or those being underweight or obese. Our results highlight the need for careful nutritional management and multidisciplinary approach for these patients. A higher resolution version of the Graphical abstract is available as Supplementary information.

Pregnancy after living kidney donation, a systematic review of the available evidence, and a review of the current guidance.

Understanding and communicating the risk of pregnancy complications post-living kidney donation is imperative as the majority of living kidney donors (LKD) are women of childbearing age. We aimed to identify all original research articles examining complications in post-donation pregnancies and compared the quality and consistency of related guidelines. We searched Embase, MEDLINE, PubMed, society webpages, and guideline registries for English-language publications published up until December 18, 2020. Ninety-three articles were screened from which 16 studies were identified, with a total of 1399 post-donation pregnancies. The outcome of interest, post-donation pregnancy complications, was not calculable, and only a narrative synthesis of the evidence was possible. The absolute risk of pre-eclampsia increased from ~1%-3% pre-donation (lower than the general population) to ~4%-10% post-donation (comparable to the general population). The risks of adverse fetal and neonatal outcomes were no different between post-donation and pre-donation pregnancies. Guidelines and consensus statements were consistent in stating the need to inform LKDs of their post-donation pregnancy risk, however, the depth and scope of this guidance were variable. While the absolute risk of pregnancy complications remains low post-donation, a concerted effort is required to better identify and individualize risk in these women, such that consent to donation is truly informed.

Incidence of Kidney Replacement Therapy and Subsequent Outcomes Among Patients With Systemic Lupus Erythematosus: Findings From the ERA Registry.

RATIONALE & OBJECTIVE: There is a dearth of data characterizing patients receiving kidney replacement therapy (KRT) for kidney failure due to systemic lupus erythematosus (SLE) and their clinical outcomes. The aim of this study was to describe trends in incidence and prevalence of KRT among these patients as well as to compare their outcomes versus those of patients treated with KRT for diseases other than SLE. STUDY DESIGN: Retrospective cohort study based on kidney registry data. SETTING & PARTICIPANTS: Patients recorded in 14 registries of patients receiving KRT that provided data to the European Renal Association Registry between 1992 and 2016. PREDICTOR: SLE as cause of kidney failure. OUTCOMES: Incidence and prevalence of KRT, patient survival while receiving KRT, patient and graft survival after kidney transplant, and specific causes of death. ANALYTICAL APPROACH: Kaplan-Meier methods and Cox regression models were fit to compare patient survival between the SLE and non-SLE groups, overall KRT, dialysis, and patient and graft survival after kidney transplant. RESULTS: In total, 1,826 patients commenced KRT for kidney failure due to SLE, representing an incidence of 0.80 per million population (pmp) per year. The incidence remained stable during the study period (annual percent change, 0.1% [95% CI, -0.6% to 0.8%]). Patient survival among patients with SLE receiving KRT was similar to survival in the comparator group (hazard ratio [HR], 1.11 [95% CI, 0.99-1.23]). After kidney transplant, the risk of death was greater among patients with SLE than among patients in the comparator group (HR, 1.25 [95% CI, 1.02-1.53]), whereas the risk of all-cause graft failure was similar (HR, 1.09 [95% CI, 0.95-1.27]). Ten-year patient overall survival during KRT and patient and graft survival after kidney transplant improved over the study period (HRs of 0.71 [95% CI, 0.56-0.91], 0.43 [95% CI, 0.27-0.69], and 0.60 [95% CI, 0.43-0.84], respectively). Patients with SLE receiving KRT were significantly more likely to die of infections (24.8%) than patients in the comparator group (16.9%; P < 0.001). LIMITATIONS: No data were available on extrarenal manifestations of SLE, drug treatments, comorbidities, kidney transplant characteristics, or relapses of SLE. CONCLUSIONS: The prognosis of patients with SLE receiving KRT has improved over time. Survival of patients with SLE who required KRT was similar compared with patients who required KRT for other causes of kidney failure. Survival following kidney transplants was worse among patients with SLE.