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Rationale & Objective: Low muscle mass is common among older adults and associated with poor prognosis. Quantifying muscle mass is challenging in routine clinical practice. We hypothesized that glomerular filtration of creatinine (GF cr ) reflects muscle mass, and previously proposed estimated GF cr (eGF cr ), as a practical index of muscle mass in older adults. This study investigated whether measured GF cr (mGF cr ) and eGF cr are similarly associated with the direct measure of muscle mass, the thigh total muscle lean area (TTMLA)., Study Design: Cross-sectional analysis of a community-based prospective cohort., Setting & Participants: A total of 794 older adults with measured glomerular filtration rate (mGFR) and TTMLA in the AGES-Reykjavik Study., Exposure: Measured GF cr , the product of serum creatinine (Scr) and mGFR obtained using plasma iohexol clearance and eGF cr , the product of Scr and estimated glomerular filtration rate using serum cystatin C (Scys)., Outcome: TTMLA measured using computed tomography., Analytical Approach: Sex-specific Pearson's correlation and linear regression analyses using continuous and categorical mGF cr and eGF cr . Covariates included demographic, behavioral, and clinical variables, and comorbid conditions., Results: The mean age and mGFR were 80.3±4.0 (SD) years and 62.3±16.5 (SD) mL/min/1.73m 2 , respectively. The lowest sex-specific tertile of mGF cr , compared with the highest tertile, was associated with a 14.6 (95% CI, 11.5-17.6) cm 2 /1.73m 2 lower TTMLA in men, and a 7.9 (95% CI, 5.5-10.2) cm 2 /1.73m 2 lower TTMLA in women. Significant associations were observed between eGF cr and TTMLA. Correlations of eGF cr with TTMLA were generally as strong or stronger than correlations of alternative indices derived from Scr and Scys., Limitations: Residual confounding by measured and unmeasured variables., Conclusions: These findings support the validity of GF cr as an index of muscle mass among older adults and the use of eGF cr as a practical alternative to mGF cr in the clinical setting., Plain-Language Summary: Low muscle mass is common among older adults and is associated with poor clinical outcomes. Quantifying muscle mass is challenging in routine clinical practice. We evaluated whether glomerular filtration of creatinine (GF cr ) could serve as an index of muscle mass. We performed a cross-sectional study including 794 older adults who underwent computed tomography for thigh muscle lean area as a directly measured indicator of total body muscle mass. Significant positive associations between thigh muscle lean area and both measured GF cr (serum creatinine [Scr] ×measured glomerular filtration rate [GFR]) and estimated GF cr (Scr ×estimated GFR based on serum cystatin C [Scys]), a more practical index, were shown. These findings suggest the value of using eGF cr , a simply obtained novel index in the clinical setting, to assess muscle mass among older adults., (Copyright © 2024 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.)

Abstract: Hypercalcemia in monoclonal gammopathy of undetermined significance (MGUS) presents a clinical challenge because it may indicate progression to multiple myeloma (MM) but could also be due to a multitude of unrelated disorders. To inform the approach to this clinical challenge, we conducted a nested cohort study within the Iceland Screens, Treats, or Prevents Multiple Myeloma screening study. Of the 75 422 Icelanders aged 40 years and above who underwent screening for MGUS, we included 2546 with MGUS who were in active follow-up, including regular serum calcium measurements. In total, 191 individuals (7.5%) had hypercalcemia detected at least once, of whom 93 had persistent hypercalcemia (48.7%). MM was found in 3 participants with persistent hypercalcemia (3.2%); all had concurrent bone disease and other end-organ damage. The most common causes of hypercalcemia were primary hyperparathyroidism (56.0%) and malignancies other than MM (16.0%). In this first comprehensive study on hypercalcemia in MGUS, we observed that hypercalcemia rarely indicated MGUS progression and never in the absence of other symptoms of MM. More than half of hypercalcemia cases were transient, and the underlying causes were similar to those in the general population. We conclude that hypercalcemia in MGUS should be approached in the same way as in those without MGUS., (© 2025 American Society of Hematology. Published by Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.)

Background and Hypothesis: Knowledge regarding access to first kidney transplantation (KT) and subsequent KT in patients commencing kidney replacement therapy (KRT) in childhood is limited., Methods: Using European Renal Association (ERA) Registry data, we investigated European patients who started KRT below 20 years of age between 1978 and 2019. Access and determinants to first, second and third KT were assessed using multivariable Cox regression., Results: 12 623, 4077, and 1186 patients were included while awaiting first, second and third KT, at median ages of 13.8 (IQR: 7.5-17.4), 20.9 (IQR: 16.5-26.1) and 26.6 (IQR: 20.3-32.8) years, respectively. During the study period, overall access was 87.8%, 72.7% and 60.5% for first, second and third KT, respectively, and median time to each KT was 0.9 (IQR: 0.2-2.1), 1.9 (0.6-4.5) and 2.6 (IQR: 1.0-5.3) years. Younger age at KRT initiation (aHR 0-4 vs. 10-14 years: 0.54; 95%CI: 0.51-0.57) and female sex (HR: 0.94; 95%CI: 0.90-0.98) were associated with lower access to first KT. KT candidates between 15-19 years had lower access to first and second KT (aHR: 0.69; 95%CI: 0.66-0.73, and aHR: 0.70; 95%CI: 0.61-0.81) compared to 10-14 year-olds. Compared to CAKUT, glomerulonephritis patients had lower access to KT (aHR: 0.75; 95%CI: 0.71-0.80 for first, aHR: 0.89; 95%CI: 0.81-0.98 for second and aHR: 0.80; 95%CI: 0.66-0.97 for third KT). Similarly, patients with primary renal diseases with high risk of recurrence, had lower chances of receiving a first and second KT (aHR: 0.80; 95%CI: 0.76-0.85 for first, aHR: 0.86; 95%CI: 0.78-0.95 for second KT). Access to re-transplantation was also higher with prior pre-emptive KT and previous graft survival exceeding five years., Conclusion: Our study highlights KT access disparities particularly for females, the youngest recipients, high-risk age (15-19 years), and diseases with recurrence risk. Notably, pre-emptive transplants and enduring previous grafts offer advantages regarding re-transplantation., (© The Author(s) 2025. Published by Oxford University Press on behalf of the ERA.)

Background and Hypothesis: Causes and risk factors for community-acquired acute kidney injury (CA-AKI) have not been thoroughly studied. The aim of this study was to examine the risk factors for CA-AKI., Methods: In this prospective study, we examined serum creatinine from all individuals visiting a university hospital's emergency department (ED) over an 11-month period for the presence of AKI defined according to the KDIGO criteria. Patients with AKI were invited to participate. Randomly selected controls (1:2) were paired according to age, sex, and date of admission. Participants answered questions about their medical history and medication use, including over-the-counter (OTC) drugs. Conditional logistic regression was used to identify factors associated with AKI., Results: Of 602 AKI cases identified, 512 participated in the study. AKI cases were significantly more likely than controls to have used nonsteroidal anti-inflammatory drugs (NSAIDs) (26.0 % vs 18.0 %, p = 0,001) in the week preceding the ED visit, particularly OTC NSAIDs (23.3 % vs 15.9 %, p < 0.001). AKI was associated with a recent history of vomiting (OR 2.52 [95 %CI 1.87-3.39]), diarrhea (1.30 [1.00-1.70]) and urinary retention (1.92 [1.36-2.72]), use of non-selective NSAIDs (1.84, [1.37-2.48]), RAAS blockers (1.63 [1.21-2.19]), and diuretics (1.53 [1.13-2.08]), and a history of diabetes (1.42 [1.04-1.94]), CKD (1.36 [1.01-1.83]) and smoking (1.72 [1.24-2.37])., Conclusions: Events in the setting of acute illness and medication use, including OTC NSAIDs, may play a greater role in the development of CA-AKI than comorbid conditions. Frequent use of OTC NSAIDs is a concern and should be addressed in view of serious adverse effects., (Copyright © 2024. Published by Elsevier B.V.)

Monoclonal gammopathy of undetermined significance (MGUS) is the asymptomatic precursor of multiple myeloma and related diseases but has also been associated with thrombosis. Prior studies have not been based on screened cohorts leading to bias. We assessed the risk of thrombosis in a cohort of 75 422 individuals over 40 years old who were screened for MGUS in Iceland. We also evaluated the association of M protein concentration with thrombotic risk. A total of 3668 participants had MGUS. After a median follow-up of ~3.7 years, 124 venous and 252 arterial thrombotic events (10.3 and 21.0 per 1000 person years respectively) were observed in the MGUS group, compared to 1509 and 3471 in the non-MGUS group (6.0 and 13.8 per 1000 person years respectively). After adjusting for multiple confounders, MGUS was associated with an increased risk of venous thrombosis (hazard ratio [HR] = 1.43; 95% confidence interval [CI]: 1.19-1.73) but not arterial thrombosis (HR = 0.96; 95% CI: 0.87-1.13). M protein concentration was not associated with venous (p = 0.72) or arterial (p = 0.95) thrombosis. The findings show, in a screened cohort, that MGUS is associated with venous, but not arterial, thrombosis. Furthermore, they suggest that there is a subset of individuals with MGUS with subclinical monoclonal gammopathy of thrombotic significance., (© 2024 British Society for Haematology and John Wiley & Sons Ltd.)

Background: The association between lithium use and chronic kidney disease, and the effect of comorbidities on this association are poorly understood. Our aim was to examine the risk of developing stage 3 or higher chronic kidney disease among people receiving lithium therapy., Methods: This was a retrospective, population-based cohort study of all adults (aged ≥18 years) in Iceland treated with lithium for a mood disorder who had two or more serum creatinine measurements available in the years 2008-17, irrespective of duration of lithium therapy, identified from the Prescription Medicines Register of the Directorate of Health, or through blood lithium measurements. The control group comprised all eligible outpatients with mood disorders (ICD-10 codes F30-F39) who had not been prescribed lithium and who had attended the national tertiary referral centre in 2014-16. Individuals with chronic kidney disease (identified by ICD codes or an estimated glomerular filtration rate [eGFR] <60 mL/min per 1·73 m 2 ) before Jan 1, 2008, or those with glomerular disease, genetic or congenital kidney disease, or small kidneys diagnosed before or after 2008 were excluded. Chronic kidney disease stages 3 and higher were defined according to the 2012 Kidney Disease: Improving Global Outcomes Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease, and the eGFR was calculated from serum creatinine; all ICD-10 and ICD-9 diagnosis codes, serum creatinine and blood lithium concentrations, and urine albumin-to-creatinine ratios were obtained from health-care institutions and laboratories. Risk of developing stage 3 or higher chronic kidney disease between Jan 1, 2008, and Dec 31, 2017, was assessed using time-to-event regression analysis, accounting for competing risk of death. People with lived experience were not involved in the design or conduct of this study., Findings: We identified 4310 individuals (2695 who had received lithium and 1615 control participants), of whom 3198 were included in the study. 2025 (75·1%) individuals in the lithium group (1165 [57·5%] female and 860 [42·5%] male) and 1173 (72·6%) in the control group (737 [62·8%] female and 436 [37·2%] male) were included in the study at end of follow-up. The mean age of the study sample at the end of follow-up was 46·6 years (SD 16·4; range 18·5-98·9). Ethnicity data were not available. In the lithium group, 211 (10·4%) of 2025 individuals developed stage 3 or higher chronic kidney disease, compared with 35 (3·0%) of 1173 individuals in the control group (hazard ratio [HR] 1·90, 95% CI 1·32-2·75 after adjusting for sex, age, and comorbid conditions). Compared with control participants, the risk of stage 3 or higher chronic kidney disease was significantly increased for subgroups with a mean blood lithium concentration of 0·60-0·79 mmol/L (HR 2·93, 95% CI 1·97-4·36) or 0·80-0·99 mmol/L (4·31, 2·66-6·99), but not for the subgroup with a mean blood lithium concentration of 0·30-0·59 mmol/L (1·22, 0·78-1·90). Analyses also showed that age, initial eGFR, diabetes, and history of acute kidney injury were significant risk factors for developing stage 3 or higher chronic kidney disease., Interpretation: Individuals with mood disorders receiving lithium treatment had an increased risk of developing stage 3 or higher chronic kidney disease in a blood concentration-dependent manner. We also found that other factors, including age, initial eGFR, and comorbidities were associated with increased risk of for developing stage 3 or higher chronic kidney disease. Overall, our findings suggest that in addition to considering other risk factors (eg, age or clinical comorbidities), careful monitoring of blood lithium concentrations and use of the lowest effective lithium dose for adequate mood stabilisation is recommended for helping to mitigate the risk of chronic kidney disease., Funding: Akureyri Hospital Research Fund and Landspitali University Hospital Science Fund., Competing Interests: Declaration of interests We declare no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved, including those for text and data mining, AI training, and similar technologies.)

Mendelian Randomization studies indicate that BMI contributes to various diseases, but it's unclear if this is entirely mediated by BMI itself. This study examines whether disease risk from BMI-associated sequence variants is mediated through BMI or other mechanisms, using data from Iceland and the UK Biobank. The associations of BMI genetic risk score with diseases like fatty liver disease, knee replacement, and glucose intolerance were fully attenuated when conditioned on BMI, and largely for type 2 diabetes, heart failure, myocardial infarction, atrial fibrillation, and hip replacement. Similar attenuation was observed for chronic kidney disease and stroke, though results varied. Findings were consistent across sexes, except for myocardial infarction. Residual effects may result from temporal BMI changes, pleiotropy, measurement error, non-linear relationships, non-collapsibility, or confounding. The attenuation extent of BMI genetic risk score on disease associations suggests the potential impact of reducing BMI on disease risk., Competing Interests: Competing interests G.E., G.T., V.S., F.Z., H.Helgason, T.O., S.R., V.T., M.O.U., G.S., A.S.S., H.E., H.M.A., G.A.J., A.H., S.G., U.S., H.K.A., D.O.A., G.B., H.S., T.T., P.S., U.T., H.Holm, D.F.G. and K.S. are employees of deCODE Genetics/Amgen Inc. The remaining authors declare no competing interests., (© 2024. The Author(s).)

Background: Inherited kidney diseases (IKD) and congenital anomalies of the kidney and urinary tract (CAKUT) are causes of kidney failure requiring kidney replacement therapy (KRT) that major renal registries usually amalgamate into the primary renal disease (PRD) category 'miscellaneous' or in the glomerulonephritis or pyelonephritis categories. This makes IKDs invisible (except for polycystic kidney disease) and may negatively influence the use of genetic testing, which may identify a cause for IKDs and some CAKUT., Methods: We have re-examined the etiology of KRT by composing a separate IKD and CAKUT PRD group using data from the European Renal Association (ERA) Registry., Results: In 2019, IKD-CAKUT was the fourth most common cause of kidney failure among incident KRT patients, accounting for 8.9% of cases (IKD 7.4% [including 5.0% ADPKD], CAKUT 1.5%), behind diabetes (23.0%), hypertension (14.4%) and glomerulonephritis (10.6%). IKD-CAKUT was the most common cause of kidney failure among patients younger than 20 years (41.0% of cases), but their incidence rate was highest among those aged 45-74 years (22.5 per million age-related population). Among prevalent KRT patients, IKD-CAKUT (18.5%) and glomerulonephritis (18.7%) were the two most common causes of kidney failure overall, while IKD-CAKUT was the most common cause in women (21.6%) and in patients younger than 45 years (29.1%)., Conclusion: IKD and CAKUT are common causes of kidney failure among KRT patients. Distinct categorization of IKD and CAKUT better characterizes the epidemiology of the causes of chronic kidney disease, and highlights the importance of genetic testing in the diagnostic workup of CKD., (© The Author(s) 2024. Published by Oxford University Press on behalf of the ERA.)

Background: In 2020, the coronavirus disease 2019 (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. Changes occurring during the first and second waves of the pandemic were also 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 was greatest 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 decrease. In dialysis patients, mortality increased by 11.4% and was highest in those 65-74 years of age (16.1%), in those with diabetes as the 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 = 317 787) resembled that of 2019 (N = 317 077)., 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., (© The Author(s) 2024. Published by Oxford University Press on behalf of the ERA.)

Rationale & Objective: Diabetic kidney disease (DKD) is one of the leading causes of end-stage kidney disease globally. We aim to identify proteomic and metabolomic correlates of histologically confirmed DKD that may improve our understanding of its pathophysiology., Study Design: A cross-sectional study., Setting & Participants: A total of 434 Boston Kidney Biopsy Cohort participants., Predictors: Histopathological diagnosis of DKD on biopsy., Outcomes: Proteins and metabolites associated with DKD., Analytical Approach: We performed linear regression to identify circulating proteins and metabolites associated with a histopathological diagnosis of DKD (n = 81) compared with normal or thin basement membrane (n = 27), and other kidney diseases without diabetes (n = 279). Pathway enrichment analysis was used to explore biological pathways enriched in DKD. Identified proteins were assessed for their discriminative ability in cases of DKD versus a distinct set of 48 patients with diabetes but other kidney diseases., Results: After adjusting for age, sex, estimated glomerular filtration, and albuminuria levels, there were 8 proteins and 1 metabolite that differed between DKD and normal/thin basement membrane, and 84 proteins and 11 metabolites that differed between DKD and other kidney diseases without diabetes. Five proteins were significant in both comparisons: C-type mannose receptor 2, plexin-A1, plexin-D1, renin, and transmembrane glycoprotein NMB. The addition of these proteins improved discrimination over clinical variables alone of a histopathological diagnosis of DKD on biopsy among patients with diabetes (change in area under the curve 0.126; P  = 0.008)., Limitations: A cross-sectional approach and lack of an external validation cohort., Conclusions: Distinct proteins and biological pathways are correlated with a histopathological diagnosis of DKD., (© 2024 The Authors.)

International consensus supports the development of standardized protocols for measured glomerular filtration rate (mGFR) to facilitate the integration of mGFR testing in both clinical and research settings. To this end, the European Kidney Function Consortium convened an international group of experts with relevant experience in mGFR. The working group performed an extensive literature search to inform the development of recommendations for mGFR determination using 1-compartment plasma clearance models and iohexol as the exogenous filtration marker. Iohexol was selected as it is non-radio labeled, inexpensive, and safe, can be assayed at a central laboratory, and the other commonly used non-radio-labeled tracers have been (inulin) or are soon to be (iothalamate) discontinued. A plasma clearance model was selected over urine clearance as it requires no urine collection. A 1 compartment was preferred to 2 compartments as it requires fewer samples. The recommendations are based on published evidence complemented by expert opinion. The consensus paper covers practical advice for patients and health professionals, preparation, administration, and safety aspects of iohexol, laboratory analysis, blood sample collection and sampling times using both multiple and single-sample protocols, description of the mGFR mathematical calculations, as well as implementation strategies. Supplementary materials include patient and provider information sheets, standard operating procedures, a study protocol template, and support for mGFR calculation., (Copyright © 2024 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

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., (© The Author(s) 2024. Published by Oxford University Press on behalf of the ERA.)

The kidney tubules constitute two-thirds of the cells of the kidney and account for the majority of the organ's metabolic energy expenditure. Acute tubular injury (ATI) is observed across various types of kidney diseases and may significantly contribute to progression to kidney failure. Non-invasive biomarkers of ATI may allow for early detection and drug development. Using the SomaScan proteomics platform on 434 patients with biopsy-confirmed kidney disease, we here identify plasma biomarkers associated with ATI severity. We employ regional transcriptomics and proteomics, single-cell RNA sequencing, and pathway analysis to explore biomarker protein and gene expression and enriched biological pathways. Additionally, we examine ATI biomarker associations with acute kidney injury (AKI) in the Kidney Precision Medicine Project (KPMP) (n = 44), the Atherosclerosis Risk in Communities (ARIC) study (n = 4610), and the COVID-19 Host Response and Clinical Outcomes (CHROME) study (n = 268). Our findings indicate 156 plasma proteins significantly linked to ATI with osteopontin, macrophage mannose receptor 1, and tenascin C showing the strongest associations. Pathway analysis highlight immune regulation and organelle stress responses in ATI pathogenesis., (© 2024. The Author(s).)

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 Author(s) 2024. Published by Oxford University Press on behalf of the ERA.)

Background: Monoclonal gammopathy of undetermined significance (MGUS) is a precursor of multiple myeloma (MM) and related conditions. In previous registry-based, retrospective studies, autoimmune diseases have been associated with MGUS. However, these studies were not based on a screened population and are therefore prone to ascertainment bias., Objective: To examine whether MGUS is associated with autoimmune diseases., Design: A cross-sectional study within iStopMM (Iceland Screens, Treats, or Prevents MM), a prospective, population-based screening study of MGUS., Setting: Icelandic population of adults aged 40 years or older., Patients: 75 422 persons screened for MGUS., Measurements: Poisson regression for prevalence ratios (PRs) of MGUS among persons with or without an autoimmune disease, adjusted for age and sex., Results: A total of 10 818 participants had an autoimmune disorder, of whom 599 had MGUS (61 with a prior clinical diagnosis and 538 diagnosed at study screening or evaluation). A diagnosis of an autoimmune disease was not associated with MGUS (PR, 1.05 [95% CI, 0.97 to 1.15]). However, autoimmune disease diagnoses were associated with a prior clinical diagnosis of MGUS (PR, 2.11 [CI, 1.64 to 2.70])., Limitation: Registry data were used to gather information on autoimmune diseases, and the homogeneity of the Icelandic population may limit the generalizability of these results., Conclusion: The study did not find an association between autoimmune disease and MGUS in a systematically screened population. Previous studies not done in systematically screened populations have likely been subject to ascertainment bias. The findings indicate that recommendations to routinely screen patients with autoimmune disease for MGUS may not be warranted., Primary Funding Source: The International Myeloma Foundation and the European Research Council., Competing Interests: Disclosures: Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M23-2867.

Background: In Iceland, a small number of kidney transplants from living donors (LDs) are performed at Landspitali University Hospital (LUH) in Reykjavik, while deceased donor transplants have until recently invariably been carried out abroad. In this study, we evaluated the outcome of kidney transplantation in Icelandic patients., Methods: This was a retrospective study that included all Icelandic residents who underwent kidney transplantation between 1 January 2000 and 31 December 2019. Data were obtained from the Icelandic End-Stage Kidney Disease Registry, medical records at LUH, and the Scandiatransplant database. The Chronic Kidney Disease Epidemiology Collaboration equation was used to calculate estimated glomerular filtration rate from serum creatinine for recipients and donors aged >18 years, and the modified Schwartz equation for those aged ≤18 years. Survival was estimated using the Kaplan-Meier method, and the log-rank test was employed for group comparisons., Results: A total of 229 kidney transplants in 221 patients were performed during the 20-year period, of which 135 (58.9%) were from LDs. Transplants carried out at LUH were 118 (51.5%), of which 116 were from LDs. During a median follow-up of 7.4 years (range 0.1-20), 27 (12.2%) patients died, 20 (74%) of whom had a functioning graft. One-year patient survival was 99.1% [95% confidence interval (CI), 97.9-100], 5-year survival was 95.7% (95% CI, 92.7-98.7), and 10-year survival was 87.7% (95% CI, 82.4-93.4). Death-censored graft survival was 98.3% (95% CI, 96.6-100), 96.8% (95% CI, 94.4-99.2), and 89.2% (95% CI, 84.1-94.7) at 1, 5, and 10 years, respectively., Conclusions: Patient and graft survival are comparable with those of large transplant centers, demonstrating the feasibility of running a quality kidney transplant program in a small nation in collaboration with a larger center abroad., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2024 Palsson, Andresdottir, Jonsson, Jonsson, Hilmarsson, Indridason and Palsson.)

Background: Albuminuria is a major risk factor for chronic kidney disease (CKD) progression, especially when categorized as moderate (30 to 300 mg/g) or severe (>300 mg/g). However, there are limited data on the prognostic value of albuminuria within the normoalbuminuric range (<30 mg/g) in persons with CKD., Objective: To estimate the increase in the cumulative incidence of CKD progression with greater baseline levels of albuminuria among persons with CKD who had normoalbuminuria (<30 mg/g)., Design: Multicenter prospective cohort study., Setting: 7 U.S. clinical centers., Participants: 1629 participants meeting criteria from the CRIC (Chronic Renal Insufficiency Cohort) study with CKD (estimated glomerular filtration rate [eGFR], 20 to 70 mL/min/1.73 m 2 ) and urine albumin-creatinine ratio (UACR) less than 30 mg/g., Measurements: Baseline spot urine albumin divided by spot urine creatinine to calculate UACR as the exposure variable. The 10-year adjusted cumulative incidences of CKD progression (composite of 50% eGFR decline or kidney failure [dialysis or kidney transplantation]) from confounder adjusted survival curves using the G-formula., Results: Over a median follow-up of 9.8 years, 182 of 1629 participants experienced CKD progression. The 10-year adjusted cumulative incidences of CKD progression were 8.7% (95% CI, 5.9% to 11.6%), 11.5% (CI, 8.8% to 14.3%), and 19.5% (CI, 15.4% to 23.5%) for UACR levels of 0 to less than 5 mg/g, 5 to less than 15 mg/g, and 15 mg/g or more, respectively. Comparing persons with UACR 15 mg/g or more to those with UACR 5 to less than 15 mg/g and 0 to less than 5 mg/g, the absolute risk differences were 7.9% (CI, 3.0% to 12.7%) and 10.7% (CI, 5.8% to 15.6%), respectively. The 10-year adjusted cumulative incidence increased linearly based on baseline UACR levels., Limitation: UACR was measured once., Conclusion: Persons with CKD and normoalbuminuria (<30 mg/g) had excess risk for CKD progression, which increased in a linear fashion with higher levels of albuminuria., Primary Funding Source: None., Competing Interests: Disclosures: Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M23-2814.

Background: Monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM) are asymptomatic precursor conditions to multiple myeloma and related disorders. Smoldering multiple myeloma is distinguished from MGUS by 10% or greater bone marrow plasma cells (BMPC) on sampling, has a higher risk for progression, and requires specialist management., Objective: To develop a multivariable prediction model that predicts the probability that a person with presumed MGUS has 10% or greater BMPC (SMM or worse by bone marrow criteria) to inform the decision to obtain a bone marrow sample and compare its performance to the Mayo Clinic risk stratification model., Design: iStopMM (Iceland Screens, Treats or Prevents Multiple Myeloma), a prospective population-based screening study of MGUS. (ClinicalTrials.gov: NCT03327597)., Setting: Icelandic population of adults aged 40 years or older., Patients: 1043 persons with IgG, IgA, light-chain, and biclonal MGUS detected by screening and an interpretable bone marrow sample., Measurements: Monoclonal gammopathy of undetermined significance isotype; monoclonal protein concentration; free light-chain ratio; and total IgG, IgM, and IgA concentrations were used as predictors. Bone marrow plasma cells were categorized as 0% to 4%, 5% to 9%, 10% to 14%, or 15% or greater., Results: The c-statistic for SMM or worse was 0.85 (95% CI, 0.82 to 0.88), and calibration was excellent (intercept, -0.07; slope, 0.95). At a threshold of 10% predicted risk for SMM or worse, sensitivity was 86%, specificity was 67%, positive predictive value was 32%, and negative predictive value was 96%. Compared with the Mayo Clinic model, the net benefit for the decision to refer for sampling was between 0.13 and 0.30 higher over a range of plausible low-risk thresholds., Limitation: The prediction model will require external validation., Conclusion: This accurate prediction model for SMM or worse was developed in a population-based cohort of persons with presumed MGUS and may be used to defer bone marrow sampling and referral to hematology., Primary Funding Source: International Myeloma Foundation and the European Research Council., Competing Interests: Disclosures: Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M23-2540.

Adenine phosphoribosyltransferase (APRT) deficiency is a rare , hereditary disorder characterized by renal excretion of 2,8-dihydroxyadenine (DHA), leading to kidney stone formation and chronic kidney disease (CKD). Treatment with a xanthine oxidoreductase inhibitor, allopurinol or febuxostat, reduces urinary DHA excretion and slows the progression of CKD. The method currently used for therapeutic monitoring of APRT deficiency lacks specificity and thus, a more reliable measurement technique is needed. In this study, an ultra-performance liquid chromatography-tandem mass spectrometry method for simultaneous quantification of DHA, adenine, allopurinol, oxypurinol and febuxostat in human plasma was optimized and validated. Plasma samples were prepared with protein precipitation using acetonitrile followed by evaporation. The chemometric approach design of experiments was implemented to optimize gradient steepness, amount of organic solvent, flow rate, column temperature, cone voltage, desolvation temperature and desolvation flow rate. Experimental screening was conducted using fractional factorial design with addition of complementary experiments at the axial points for optimization of peak area, peak resolution and peak width. The assay was validated according to the US Food and Drug Administration guidelines for bioanalytical method validation over the concentration range of 50 to 5000 ng/mL for DHA, allopurinol and febuxostat, 100 to 5000 ng/mL for adenine and 50 to 12,000 ng/mL for oxypurinol, with r 2  ≥ 0.99. The analytical assay achieved acceptable performance of accuracy (-10.8 to 8.3 %) and precision (CV < 15 %). DHA, adenine, allopurinol, oxypurinol and febuxostat were stable in plasma samples after five freeze-thaw cycles at -80 °C and after storage at -80 °C for 12 months. The assay was evaluated for quantification of the five analytes in clinical plasma samples from six APRT deficiency patients and proved to be both efficient and accurate. The proposed assay will be valuable for guiding pharmacotherapy and thereby contribute to improved and more personalized care for patients with APRT deficiency., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Background: Acute kidney injury (AKI) is a serious complication following major surgery. This study examined the incidence and risk factors of AKI following orthopaedic surgeries in an Icelandic cohort, as well as the association between AKI and patient- and surgery-related factors., Methods: This retrospective cohort study comprised all patients 18 years and older who underwent orthopaedic surgeries at Landspitali - The National University Hospital in the years 2006-2018 with available serum creatinine (SCr) measurements adjacent to the surgery to stage AKI. AKI was defined according to SCr portion of the KDIGO criteria. Logistic regression was used to identify patient- and surgical factors related to progression of AKI and Poisson-regression was used to explore changes in incidence., Results: A total of 222 cases of AKI following 3208 surgeries (6.9%) were identified in the study period with a rise in the incidence by about 17% per year. Higher age (odds ratio (OR), 1.02, 95% confidence interval (CI), 1.01-1.04 per year) and underlying reduction in kidney function (OR 1.93 (1.30-2.81), 3.24 (2.08-4.96) and 4.08 (2.35-6.96) for estimated glomerular filtration rate (eGFR) of 30-59, 15-29 and <15 mL/min/1.73 m 2 compared with eGFR >60 mL/min/1.73 m 2 ) were associated with higher risk of AKI, but female sex was associated with decreased odds (OR = 0.73; 95% CI, 0.54-0.98). After correcting for age, sex, preoperative kidney function, emergency surgery and underlying comorbidities and frailty, there was an increased risk of long-term mortality in patients with AKI (HR 1.41, 95% CI 1.08-1.85), and patients who developed AKI also had accelerated progression of chronic kidney disease compared with patients who did not develop AKI., Conclusions: The incidence of AKI following orthopaedic surgeries is increasing and is associated with adverse outcomes. It is important that elderly individuals and patients who have reduced kidney function receive adequate monitoring and surveillance in the perioperative period., (© 2023 Acta Anaesthesiologica Scandinavica Foundation.)

Introduction: Cardiovascular disease is a significant cause of mortality after kidney transplantation. Whether pre-transplant screening for coronary artery disease (CAD) in asymptomatic kidney transplant candidates (KTCs) is beneficial is unclear., Methods: We conducted a retrospective cohort study evaluating post-transplant cardiovascular events in 192 high-risk KTCs who underwent pre-transplant CAD evaluation. The study aimed to identify risk factors associated with finding severe CAD on pre-transplant angiography, and to assess the relationship between screening strategies and post-transplant cardiovascular events., Results: At five years post-transplant, cardiovascular events occurred in 23.9% of subjects. Prior CAD history and left ventricular ejection fraction (LVEF) < 50% were associated with higher odds of finding severe CAD on pre-transplant angiography. Severe CAD on angiography was associated with a higher risk of early cardiovascular events within six months of transplantation. However, coronary intervention in KTCs with severe CAD was not associated with lower rates of post-transplant cardiovascular events., Conclusion: Pre-transplant coronary angiography to identify severe CAD is of highest yield in KTCs with a history of CAD or an LVEF < 50%. Our findings indicate that the identification of severe CAD in KTCs has prognostic significance for the early post-transplant period. Optimization of medical therapy in these high-risk KTCs may improve post-transplant cardiovascular outcomes., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2023 Morená, Al Jurdi, Adam, Verhoeff, Palsson, Ribas, Hullekes, Cohen Bucay, Elias and Riella.)

Objectives: Prior studies on the association of estimated glomerular filtration rate (eGFR) and mortality have failed to include methods to account for repeated eGFR determinations. The aim of this study was to estimate the association between eGFR and mortality in the general population in Iceland employing a joint model., Methods: We obtained all serum creatinine and urine protein measurements from all clinical laboratories in Iceland in the years 2008-16. Clinical data were obtained from nationwide electronic medical records. eGFR was calculated using the Chronic Kidney Disease Epidemiology Collaboration equation and categorized as follows: 0-29, 30-44, 45-59, 60-74, 75-89, 90-104 and >104 mL/min/1.73 m2. A multiple imputation method was used to account for missing urine protein data. A joint model was used to assess risk of all-cause mortality., Results: We obtained 2 120 147 creatinine values for 218 437 individuals, of whom 84 364 (39%) had proteinuria measurements available. Median age was 46 (range 18-106) years and 47% were men. Proteinuria associated with increased risk of death for all eGFR categories in persons of all ages. In persons ≤65 years, the lowest risk was observed for eGFR of 75-89 mL/min/1.73 m2 without proteinuria. For persons aged >65 years, the lowest risk was observed for eGFR of 60-74 mL/min/1.73 m2 without proteinuria. eGFR of 45-59 mL/min/1.73 m2 without proteinuria did not associate with increased mortality risk in this age group. eGFR >104 mL/min/1.73 m2 associated with increased mortality., Conclusions: These results lend further support to the use of age-adapted eGFR thresholds for defining chronic kidney disease. Very high eGFR needs to be studied in more detail with regard to mortality., (© The Author(s) 2023. Published by Oxford University Press on behalf of the ERA.)

Background: In a population-based setting, we investigated the risks of testing positive for SARS-CoV-2 and developing severe COVID-19 outcomes among cancer patients compared with the general population., Methods: In nationwide cohorts, we identified all individuals in Norway, Denmark and Iceland who tested positive for SARS-CoV-2 or had a severe COVID-19 outcome (hospitalisation, intensive care, and death) from March until December 2020, using data from national health registries. We estimated standardised incidence ratios (SIRs) with 95% confidence intervals (CIs) comparing cancer patients with the general population., Findings: During the first wave of the pandemic, cancer patients in Norway and Denmark had higher risks of testing SARS-CoV-2 positive compared to the general population. Throughout 2020, recently treated cancer patients were more likely to test SARS-CoV-2 positive. In Iceland, cancer patients experienced no increased risk of testing positive. The risk of COVID-19-related hospitalisation was higher among cancer patients diagnosed within one year of hospitalisation (Norway: SIR = 2.43, 95% CI 1.89-3.09; Denmark: 2.23, 1.96-2.54) and within five years (Norway: 1.58, 1.35-1.83; Denmark: 1.54, 1.42-1.66). Risks were higher in recently treated cancer patients and in those diagnosed with haematologic malignancies, colorectal or lung cancer. Risks of COVID-19-related intensive care and death were higher among cancer patients., Interpretation: Cancer patients were at increased risk of testing positive for SARS-CoV-2 during the first pandemic wave when testing availability was limited, while relative risks of severe COVID-19 outcomes remained increased in cancer patients throughout 2020. Recent cancer treatment and haematologic malignancy were the strongest risk factors., Funding: Nordic Cancer Union., Competing Interests: ML declares stock or stock options in Astra Zeneca and Pfizer Inc. The other authors declare no competing interests., (© 2023 The Author(s).)

Background: Persistent symptoms are common after SARS-CoV-2 infection but correlation with objective measures is unclear., Methods: We invited all 3098 adults who tested SARS-CoV-2 positive in Iceland before October 2020 to the deCODE Health Study. We compared multiple symptoms and physical measures between 1706 Icelanders with confirmed prior infection (cases) who participated, and 619 contemporary and 13,779 historical controls. Cases participated in the study 5-18 months after infection., Results: Here we report that 41 of 88 symptoms are associated with prior infection, most significantly disturbed smell and taste, memory disturbance, and dyspnea. Measured objectively, cases had poorer smell and taste results, less grip strength, and poorer memory recall. Differences in grip strength and memory recall were small. No other objective measure associated with prior infection including heart rate, blood pressure, postural orthostatic tachycardia, oxygen saturation, exercise tolerance, hearing, and traditional inflammatory, cardiac, liver, and kidney blood biomarkers. There was no evidence of more anxiety or depression among cases. We estimate the prevalence of long Covid to be 7% at a median of 8 months after infection., Conclusions: We confirm that diverse symptoms are common months after SARS-CoV-2 infection but find few differences between cases and controls in objective parameters measured. These discrepancies between symptoms and physical measures suggest a more complicated contribution to symptoms related to prior infection than is captured with conventional tests. Traditional clinical assessment is not expected to be particularly informative in relating symptoms to a past SARS-CoV-2 infection., (© 2023. The Author(s).)

Importance: Histologic lesions in the kidney may reflect or contribute to systemic processes that may lead to adverse cardiovascular events., Objective: To assess the association between kidney histopathologic lesion severity and the risk of incident major adverse cardiovascular events (MACE)., Design, Setting, and Participants: This prospective observational cohort study included participants without a history of myocardial infarction, stroke, or heart failure from the Boston Kidney Biopsy Cohort recruited from 2 academic medical centers in Boston, Massachusetts. Data were collected from September 2006 and November 2018, and data were analyzed from March to November 2021., Exposures: Semiquantitative severity scores for kidney histopathologic lesions adjudicated by 2 kidney pathologists, a modified kidney pathology chronicity score, and primary clinicopathologic diagnostic categories., Main Outcomes and Measures: The main outcome was the composite of death or incident MACE, which included myocardial infarction, stroke, and heart failure hospitalization. All cardiovascular events were independently adjudicated by 2 investigators. Cox proportional hazards models estimated associations of histopathologic lesions and scores with cardiovascular events adjusted for demographic characteristics, clinical risk factors, estimated glomerular filtration rate (eGFR), and proteinuria., Results: Of 597 included participants, 308 (51.6%) were women, and the mean (SD) age was 51 (17) years. The mean (SD) eGFR was 59 (37) mL/min per 1.73 m2, and the median (IQR) urine protein to creatinine ratio was 1.54 (0.39-3.95). The most common primary clinicopathologic diagnoses were lupus nephritis, IgA nephropathy, and diabetic nephropathy. Over a median (IQR) of 5.5 (3.3-8.7) years of follow-up, the composite of death or incident MACE occurred in 126 participants (37 per 1000 person-years). Compared with the reference group of individuals with proliferative glomerulonephritis, the risk of death or incident MACE was highest in individuals with nonproliferative glomerulopathy (hazard ratio [HR], 2.61; 95% CI, 1.30-5.22; P = .002), diabetic nephropathy (HR, 3.56; 95% CI, 1.62-7.83; P = .002), and kidney vascular diseases (HR, 2.86; 95% CI, 1.51-5.41; P = .001) in fully adjusted models. The presence of mesangial expansion (HR, 2.98; 95% CI, 1.08-8.30; P = .04) and arteriolar sclerosis (HR, 1.68; 95% CI, 1.03-2.72; P = .04) were associated with an increased risk of death or MACE. Compared with minimal chronicity, greater chronicity was significantly associated with an increased risk of death or MACE (severe: HR, 2.50; 95% CI, 1.06-5.87; P = .04; moderate: HR, 1.66; 95% CI, 0.74-3.75; P = .22; mild: HR, 2.22; 95% CI, 1.01-4.89; P = .047) in fully adjusted models., Conclusions and Relevance: In this study, specific kidney histopathological findings were associated with increased risks of CVD events. These results provide potential insight into mechanisms of the heart-kidney relationship beyond those provided by eGFR and proteinuria.

Rationale & Objectives: The urine-to-plasma (U/P) ratio of urea is correlated with urine-concentrating capacity and associated with progression of autosomal dominant polycystic kidney disease. As a proposed biomarker of tubular function, we hypothesized that the U/P urea ratio would also be associated with progression of more common forms of chronic kidney disease (CKD)., Study Design: Observational cohort study., Setting & Participants: 3,723 adults in the United States with estimated glomerular filtration rate (eGFR) of 20-70 mL/min/1.73 m 2 , enrolled in the Chronic Renal Insufficiency Cohort (CRIC) Study., Exposure: U/P urea ratio, calculated from 24-hour urine collections and plasma samples at baseline., Outcome: Associations of U/P urea ratio with eGFR slope, initiation of kidney replacement therapy (KRT), and CKD progression, defined as 50% decline in eGFR or incident KRT., Analytical Approach: Multivariable linear mixed-effects models tested associations with eGFR slope. Cox proportional hazards models tested associations with dichotomous CKD outcomes., Results: The median U/P urea ratio was 14.8 (IQR, 9.5-22.2). Compared with participants in the highest U/P urea ratio quintile, those in the lowest quintile had a greater eGFR decline by 1.06 mL/min/1.73 m 2 per year (P < 0.001) over 7.0 (IQR, 3.0-11.0) years of follow-up observation. Each 1-SD lower natural log-transformed U/P urea ratio was independently associated with CKD progression (HR, 1.22 [95% CI, 1.12-1.33]) and incident KRT (HR, 1.22 [95% CI, 1.10-1.33]). Associations differed by baseline eGFR (P interaction = 0.009). Among those with an eGFR ≥30 mL/min/1.73 m 2 , each 1-SD lower in ln(U/P urea ratio) was independently associated with CKD progression (HR, 1.30 [95% CI, 1.18-1.45]), but this was not significant among those with eGFR <30 mL/min/1.73 m 2 (HR, 1.00 [95% CI, 0.84-1.20])., Limitations: Possibility of residual confounding. Single baseline 24-hour urine collection for U/P urea ratio., Conclusions: In a large and diverse cohort of patients with common forms of CKD, U/P urea was independently associated with disease progression and incident kidney failure. Associations were not significant among those with advanced CKD at baseline., (Copyright © 2022 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.)

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., (© The Author(s) 2022. Published by Oxford University Press on behalf of the ERA.)

Serum free light chain (FLC) concentration is greatly affected by kidney function. Using a large prospective population-based cohort, we aimed to establish a reference interval for FLCs in persons with chronic kidney disease (CKD). A total of 75422 participants of the iStopMM study were screened with serum FLC, serum protein electrophoresis and immunofixation. Estimated glomerular filtration rate (eGFR) was calculated from serum creatinine. Central 99% reference intervals were determined, and 95% confidence intervals calculated. Included were 6461 (12%) participants with measured FLCs, eGFR < 60 mL/min/1.73 m 2 , not receiving renal replacement therapy, and without evidence of monoclonality. Using current reference intervals, 60% and 21% had kappa and lambda FLC values outside the normal range. The FLC ratio was outside standard reference interval (0.26-1.65) in 9% of participants and outside current kidney reference interval (0.37-3.10) in 0.7%. New reference intervals for FLC and FLC ratio were established. New reference intervals for the FLC ratio were 0.46-2.62, 0.48-3.38, and 0.54-3.30 for eGFR 45-59, 30-44, and < 30 mL/min/1.73 m 2 groups, respectively. The crude prevalence of LC-MGUS in CKD patients was 0.5%. We conclude that current reference intervals for FLC and FLC ratio are inaccurate in CKD patients and propose new eGFR based reference intervals to be implemented., (© 2022. The Author(s).)

Background: Protein biomarkers may provide insight into kidney disease pathology but their use for the identification of phenotypically distinct kidney diseases has not been evaluated., Methods: We used unsupervised hierarchical clustering on 225 plasma biomarkers in 541 individuals enrolled into the Boston Kidney Biopsy Cohort, a prospective cohort study of individuals undergoing kidney biopsy with adjudicated histopathology. Using principal component analysis, we studied biomarker levels by cluster and examined differences in clinicopathologic diagnoses and histopathologic lesions across clusters. Cox proportional hazards models tested associations of clusters with kidney failure and death., Results: We identified three biomarker-derived clusters. The mean estimated glomerular filtration rate was 72.9 ± 28.7, 72.9 ± 33.4 and 39.9 ± 30.4 mL/min/1.73 m 2 in Clusters 1, 2 and 3, respectively. The top-contributing biomarker in Cluster 1 was AXIN, a negative regulator of the Wnt signaling pathway. The top-contributing biomarker in Clusters 2 and 3 was Placental Growth Factor, a member of the vascular endothelial growth factor family. Compared with Cluster 1, individuals in Cluster 3 were more likely to have tubulointerstitial disease ( P  < .001) and diabetic kidney disease ( P  < .001) and had more severe mesangial expansion [odds ratio (OR) 2.44, 95% confidence interval (CI) 1.29, 4.64] and inflammation in the fibrosed interstitium (OR 2.49 95% CI 1.02, 6.10). After multivariable adjustment, Cluster 3 was associated with higher risks of kidney failure (hazard ratio 3.29, 95% CI 1.37, 7.90) compared with Cluster 1., Conclusion: Plasma biomarkers may identify clusters of individuals with kidney disease that associate with different clinicopathologic diagnoses, histopathologic lesions and adverse outcomes, and may uncover biomarker candidates and relevant pathways for further study., (© The Author(s) 2022. Published by Oxford University Press on behalf of the ERA.)

Background: The severity of SARS-CoV-2 infection varies from asymptomatic state to severe respiratory failure and the clinical course is difficult to predict. The aim of the study was to develop a prognostic model to predict the severity of COVID-19 in unvaccinated adults at the time of diagnosis., Methods: All SARS-CoV-2-positive adults in Iceland were prospectively enrolled into a telehealth service at diagnosis. A multivariable proportional-odds logistic regression model was derived from information obtained during the enrollment interview of those diagnosed between February 27 and December 31, 2020 who met the inclusion criteria. Outcomes were defined on an ordinal scale: (1) no need for escalation of care during follow-up; (2) need for urgent care visit; (3) hospitalization; and (4) admission to intensive care unit (ICU) or death. Missing data were multiply imputed using chained equations and the model was internally validated using bootstrapping techniques. Decision curve analysis was performed., Results: The prognostic model was derived from 4756 SARS-CoV-2-positive persons. In total, 375 (7.9%) only required urgent care visits, 188 (4.0%) were hospitalized and 50 (1.1%) were either admitted to ICU or died due to complications of COVID-19. The model included age, sex, body mass index (BMI), current smoking, underlying conditions, and symptoms and clinical severity score at enrollment. On internal validation, the optimism-corrected Nagelkerke's R 2 was 23.4% (95%CI, 22.7-24.2), the C-statistic was 0.793 (95%CI, 0.789-0.797) and the calibration slope was 0.97 (95%CI, 0.96-0.98). Outcome-specific indices were for urgent care visit or worse (calibration intercept -0.04 [95%CI, -0.06 to -0.02], E max 0.014 [95%CI, 0.008-0.020]), hospitalization or worse (calibration intercept -0.06 [95%CI, -0.12 to -0.03], E max 0.018 [95%CI, 0.010-0.027]), and ICU admission or death (calibration intercept -0.10 [95%CI, -0.15 to -0.04] and E max 0.027 [95%CI, 0.013-0.041])., Conclusion: Our prognostic model can accurately predict the later need for urgent outpatient evaluation, hospitalization, and ICU admission and death among unvaccinated SARS-CoV-2-positive adults in the general population at the time of diagnosis, using information obtained by telephone interview., (© 2022. The Author(s).)

Memory T-cell responses following SARS-CoV-2 infection have been extensively investigated but many studies have been small with a limited range of disease severity. Here we analyze SARS-CoV-2 reactive T-cell responses in 768 convalescent SARS-CoV-2-infected (cases) and 500 uninfected (controls) Icelanders. The T-cell responses are stable three to eight months after SARS-CoV-2 infection, irrespective of disease severity and even those with the mildest symptoms induce broad and persistent T-cell responses. Robust CD4 + T-cell responses are detected against all measured proteins (M, N, S and S1) while the N protein induces strongest CD8 + T-cell responses. CD4 + T-cell responses correlate with disease severity, humoral responses and age, whereas CD8 + T-cell responses correlate with age and functional antibodies. Further, CD8 + T-cell responses associate with several class I HLA alleles. Our results, provide new insight into HLA restriction of CD8 + T-cell immunity and other factors contributing to heterogeneity of T-cell responses following SARS-CoV-2 infection., (© 2022. The Author(s).)

Objectives: All SARS-CoV-2-positive persons in Iceland were prospectively monitored and those who required outpatient evaluation or were admitted to hospital underwent protocolized evaluation that included a standardized panel of biomarkers. The aim was to describe longitudinal changes in inflammatory biomarkers throughout the infection period of patients with COVID-19 requiring different levels of care., Design: Registry-based study., Setting: Nationwide study in Iceland., Patients: All individuals who tested positive for SARS-CoV-2 by real-time polymerase chain reaction (RT-PCR) from February 28 to December 31, 2020 in Iceland and had undergone blood tests between 5 days before and 21 days following onset of symptoms., Measurements and Main Results: Data were collected from the electronic medical record system of Landspitali-The National University Hospital of Iceland. Data analyses were descriptive and the evolution of biomarkers was visualized using locally weighted scatterplot smoothing curves stratified by the worst clinical outcome experienced by the patient: outpatient evaluation only, hospitalization, and either intensive care unit (ICU) admission or death. Of 571 included patients, 310 (54.3%) only required outpatient evaluation or treatment, 202 (35.4%) were hospitalized, and 59 (10.3%) were either admitted to the ICU or died. An early and persistent separation of the mean lymphocyte count and plasma C-reactive protein (CRP) and ferritin levels was observed between the three outcome groups, which occurred prior to hospitalization for those who later were admitted to ICU or died. Lower lymphocyte count, and higher CRP and ferritin levels correlated with worse clinical outcomes. Patients who were either admitted to the ICU or died had sustained higher white blood cell and neutrophil counts, and elevated plasma levels of procalcitonin and D-dimer compared with the other groups., Conclusions: Lymphocyte count and plasma CRP and ferritin levels might be suitable parameters to assess disease severity early during COVID-19 and may serve as predictors of worse outcome., (© 2022 Acta Anaesthesiologica Scandinavica Foundation.)

Although underlying mechanisms and the clinical course of kidney disease progression are well described, less is known about potential disease reversibility. Therefore, to analyze kidney recovery, we adapted a commonly used murine chronic kidney disease (CKD) model of 2,8- dihydroxyadenine (2,8-DHA) crystal-induced nephropathy to study disease recovery and efficacy of disease-modifying interventions. The recovery phase after CKD was characterized by improved kidney function after two weeks which remained stable thereafter. By contrast, even after eight weeks recovery, tubular injury and inflammation were only partially reduced, and fibrosis persisted. Deep-learning-based histologic analysis of 8,604 glomeruli and 596,614 tubular cross sections revealed numerous tubules had undergone either prominent dilation or complete atrophy, leading to atubular glomeruli and irreversible nephron loss. We confirmed these findings in a second CKD model, reversible unilateral ureteral obstruction, in which a rapid improvement of glomerular filtration rate during recovery also did not reflect the permanent histologic kidney injury. In 2,8-DHA nephropathy, increased drinking volume was highly effective in disease prevention. However, in therapeutic approaches, high fluid intake was only effective in moderate but not severe CKD and established tissue injury was again poorly reflective of kidney function parameters. The injury was particularly localized in the medulla, which is often not analyzed. Thus, recovery after crystal- or obstruction-induced CKD is characterized by ongoing tissue injury, fibrosis, and nephron loss, but not reflected by standard measures of kidney function. Hence, our data might aid in designing kidney recovery studies and suggest the need for biomarkers specifically monitoring intra-kidney tissue injury., (Copyright © 2022 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Background and Objectives: High tacrolimus intrapatient variability has been associated with inferior graft outcomes in patients with kidney transplants. We studied baseline patterns of tacrolimus intrapatient variability in pediatric patients with kidney transplants and examined these patterns in relation to C1q-binding de novo donor-specific antibodies., Design, Setting, Participants, & Measurements: All tacrolimus levels in participants who underwent kidney-only transplantation at a single pediatric center from 2004 to 2018 (with at least 12-month follow-up, followed until 2019) were analyzed to determine baseline variability. Intrapatient variability was defined using the coefficient of variation (SD/mean ×100%) of all samples in a 6-month moving window. Routine de novo donor-specific antibody measurements were available for a subgroup of patients transplanted in 2010-2018. Cox proportional hazards models using tacrolimus intrapatient variability as a time-varying variable were used to examine the association between intrapatient variability and graft outcomes. The primary outcome of interest was C1q-binding de novo donor-specific antibody formation., Results: Tacrolimus intrapatient variability developed a steady-state baseline of 30% at 10 months post-transplant in 426 patients with a combined 31,125 tacrolimus levels. Included in the outcomes study were 220 patients, of whom 51 developed C1q-binding de novo donor-specific antibodies. De novo donor-specific antibody formers had higher intrapatient variability, with a median of 38% (interquartile range, 28%-48%) compared with 28% (interquartile range, 20%-38%) for nondonor-specific antibody formers ( P <0.001). Patients with high tacrolimus intrapatient variability (coefficient of variation >30%) had higher risk of de novo donor-specific antibody formation (hazard ratio, 5.35; 95% confidence interval, 2.45 to 11.68). Patients in the top quartile of tacrolimus intrapatient variability (coefficient of variation >41%) had the strongest association with C1q-binding de novo donor-specific antibody formation (hazard ratio, 11.81; 95% confidence interval, 4.76 to 29.27)., Conclusions: High tacrolimus intrapatient variability was strongly associated with de novo donor-specific antibody formation., (Copyright © 2022 by the American Society of Nephrology.)

Objectives: The spread of SARS-CoV-2 is dependent on several factors, both biological and behavioural. The effectiveness of nonpharmaceutical interventions can be attributed largely to changes in human behaviour, but quantifying this effect remains challenging. Reconstructing the transmission tree of the third wave of SARS-CoV-2 infections in Iceland using contact tracing and viral sequence data from 2522 cases enables us to directly compare the infectiousness of distinct groups of persons., Methods: The transmission tree enables us to model the effect that a given population prevalence of vaccination would have had on the third wave had one of three different vaccination strategies been implemented before that time. This allows us to compare the effectiveness of the strategies in terms of minimizing the number of cases, deaths, critical cases, and severe cases., Results: We found that people diagnosed outside of quarantine (Rˆ=1.31) were 89% more infectious than those diagnosed while in quarantine (Rˆ=0.70) and that infectiousness decreased as a function of time spent in quarantine before diagnosis, with people diagnosed outside of quarantine being 144% more infectious than those diagnosed after ≥3 days in quarantine (Rˆ=0.54). People of working age, 16 to 66 years (Rˆ=1.08), were 46% more infectious than those outside of that age range (Rˆ=0.74)., Discussion: We found that vaccinating the population in order of ascending age or uniformly at random would have prevented more infections per vaccination than vaccinating in order of descending age, without significantly affecting the expected number of deaths, critical cases, or severe cases., (Copyright © 2022 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)