CKD: A Call for an Age-Adapted Definition

Kidney age - chronological age difference (KCD) score provides an age-adapted measure of kidney function

BACKGROUND

Given the age-related decline in glomerular filtration rate (GFR) in healthy individuals, we examined the association of all-cause death or cardiovascular event with the Kidney age - Chronological age Difference (KCD) score, whereby an individual's kidney age is estimated from their estimated GFR (eGFR) and the age-dependent eGFR decline reported for healthy living potential kidney donors.

METHODS

We examined the association between death or cardiovascular event and KCD score, age-dependent stepped eGFR criteria (eGFRstep), and eGFR < 60 ml/min/1.73 m2 (eGFR60) in a community-based high cardiovascular risk cohort of 3837 individuals aged ≥60 (median 70, interquartile range 65, 75) years, followed for a median of 5.6 years.

RESULTS

In proportional hazards analysis, KCD score ≥ 20 years (KCD20) was associated with increased risk of death or cardiovascular event in unadjusted analysis and after adjustment for age, sex and cardiovascular risk factors. Addition of KCD20, eGFRstep or eGFR60 to a cardiovascular risk factor model did not improve area under the curve for identification of individuals who experienced death or cardiovascular event in receiver operating characteristic curve analysis. However, addition of KCD20 or eGFR60, but not eGFRstep, to a cardiovascular risk factor model improved net reclassification and integrated discrimination. KCD20 identified individuals who experienced death or cardiovascular event with greater sensitivity than eGFRstep for all participants, and with greater sensitivity than eGFR60 for participants aged 60-69 years, with similar sensitivities for men and women.

CONCLUSIONS

In this high cardiovascular risk cohort aged ≥60 years, the KCD score provided an age-adapted measure of kidney function that may assist patient education, and KCD20 provided an age-adapted criterion of eGFR-related increased risk of death or cardiovascular event. Further studies that include the full age spectrum are required to examine the optimal KCD score cut point that identifies increased risk of death or cardiovascular event, and kidney events, associated with impaired kidney function, and whether the optimal KCD score cut point is similar for men and women.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00400257 , NCT00604006 , and NCT01581827 .

Proteinuria in COVID-19: prevalence, characterization and prognostic role

BACKGROUND

Proteinuria has been commonly reported in patients with COVID-19. However, only dipstick tests have been frequently used thus far. Here, the quantification and characterization of proteinuria were investigated and their association with mortality was assessed.

METHODS

This retrospective, observational, single center study included 153 patients, hospitalized with COVID-19 between March 28th and April 30th, 2020, in whom total proteinuria and urinary α1-microglobulin (a marker of tubular injury) were measured. Association with mortality was evaluated, with a follow-up until May 7th, 2020.

RESULTS

According to the Kidney Disease Improving Global Outcomes staging, 14% (n = 21) of the patients had category 1 proteinuria (< 150 mg/g of urine creatinine), 42% (n = 64) had category 2 (between 150 and 500 mg/g) and 44% (n = 68) had category 3 proteinuria (over 500 mg/g). Urine α1-microglobulin concentration was higher than 15 mg/g in 89% of patients. After a median follow-up of 27 [14;30] days, the mortality rate reached 18%. Total proteinuria and urinary α1-microglobulin were associated with mortality in unadjusted and adjusted models. This association was stronger in subgroups of patients with normal renal function and without a urinary catheter.

CONCLUSIONS

Proteinuria is frequent in patients with COVID-19. Its characterization suggests a tubular origin, with increased urinary α1-microglobulin. Tubular proteinuria was associated with mortality in COVID-19 in our restropective, observational study.

Aging and Renal Disease: Old Questions for New Challenges

Chronic kidney disease (CKD) is a growing problem among aging population, and the number of individuals at risk of end stage renal disease is rising. Part of the reason lies in incomplete understanding of the pathways underlying renal aging and kidney disease, as well as insufficient delivery of evidence-based treatment to elderly patients with CKD. This review aims to address these unsolved issues by delineating updated mechanisms of renal senescence and summarizing recent findings on key clinical aspects of CKD in the elderly. Challenges and obstacles in caring for older people with CKD are discussed, with an emphasis on modification of risk factors, prevention of acute kidney injury, stabilization of progression and decision on dialysis initiation.

Elderly Patients in a Large Nephrology Unit: Who Are Our Old, Old-Old and Oldest-Old Patients?

The world population is aging, and the prevalence of chronic kidney disease (CKD) is increasing. Whether this increase is also due to the methods currently being used to assess kidney function in the elderly is still a matter of discussion. We aimed to describe the actual referral pattern of CKD patients in a large nephrology unit and test whether the use of different formulae to estimate kidney function could affect the staging and the need for specialist care in the older subset of our population. In 2019, 1992 patients were referred to our center. Almost 28% of the patients were aged ≥80 and about 6% were ≥90 years old. Among the causes of kidney disease, glomerulonephritis displayed a higher prevalence in younger patients whereas hypertensive or diabetic kidney disease were more prevalent in older patients. The prevalence of referred patients in advanced CKD stages increased with age; estimated glomerular filtration rate (eGFR) decreased with age regardless of which equation was used (chronic kidney disease epidemiology collaboration (CKD-EPI), Lund–Malmö Revised (LMR), modification of diet in renal disease (MDRD), Full Age Spectrum (FAS), or Berlin Initiative Study 1 (BIS)). With CKD-EPI as a reference, MDRD and FAS underestimated the CKD stage while LMR overestimated it. The BIS showed the highest heterogeneity. Considering an eGFR threshold limit of 45 mL/min for defining “significant” CKD in patients over 65 years of age, the variability in CKD staging was 10% no matter which equation was used. Our study quantified the weight of “old” and “old-old” patients on follow-up in a large nephrology outpatient unit and suggested that with the current referral pattern, the type of formula used does not affect the need for CKD care within the context of a relatively late referral, particularly in elderly patients.

Age- and Sex-Specific Reference Values of Estimated Glomerular Filtration Rate in Chinese Population

BACKGROUND

Due to an aging population, prevalence and mortality of CKD continue to increase. Current CKD definition has been challenged recently. Age- and sex-specific reference values of estimated glomerular filtration rate (eGFR) in China are still lacking.

METHODS

Age- and sex-stratified, randomly selected inhabitants received a health examination and an inquest into medical history. The GFR was estimated using CKD-EPI equation. We calculated means with ±1.96 times of standard deviation and 2.5th, 97.5th percentiles of eGFR per 5-year age-group. Some of their GFRs were measured by the Gates method (99mTc-DTPA renal scintigraphy) and estimated by cystatin C-based equation.

RESULTS

The cohort study included 17,037 male and 9,304 female Chinese persons aged 18-99 years. A reference population of apparently healthy subjects was selected by excluding persons with known hypertension, diabetes, cardiovascular, or renal diseases. This healthy cohort study included 12,231 male subjects and 6,463 female subjects. The mean eGFR was higher in the female than that in the male who were younger than 40-year (122 mL/min/1.73 m2 vs. 111 mL/min/1.73 m2). In these apparently healthy persons, GFR declined approximately 0.8 mL/min/year. The lower limit of eGFR (2.5th percentile or mean minus 1.96 times of standard deviation) was <60 or 45 mL/min/1.73 m2 at the age of ≥40 or 65 years old, respectively.

CONCLUSION

The mean eGFR was higher in young females. GFR declined approximately 0.8 mL/min/year. The lower bound of eGFR was <60 mL/min/1.73 m2 or 45 mL/min/1.73 m2 at the age of ≥40 or ≥65 years, respectively. Our study provides age- and sex-specific reference values of GFR in a Chinese population.

Development and Validation of a Modified Full Age Spectrum Creatinine-Based Equation to Estimate Glomerular Filtration Rate : A Cross-sectional Analysis of Pooled Data

BACKGROUND

The Chronic Kidney Disease in Children Study (CKiD) equation for children and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation for adults are recommended serum creatinine (SCr)-based calculations for estimating glomerular filtration rate (GFR). However, these equations, as well as their combination, have limitations, notably the problem of implausible changes in GFR during the transition from adolescence to adulthood and overestimation of GFR in young adults. The full age spectrum (FAS) equation addresses these issues but overestimates GFR when SCr levels are low.

OBJECTIVE

To develop and validate a modified FAS SCr-based equation combining design features of the FAS and CKD-EPI equations.

DESIGN

Cross-sectional analysis with separate pooled data sets for development and validation.

SETTING

Research and clinical studies (n = 13) with measured GFR available.

PATIENTS

11 251 participants in 7 studies (development and internal validation data sets) and 8378 participants in 6 studies (external validation data set).

MEASUREMENTS

Clearance of an exogenous marker (reference method), SCr level, age, sex, and height were used to develop a new equation to estimate GFR.

RESULTS

The new European Kidney Function Consortium (EKFC) equation is a FAS equation with low bias (-1.2 mL/min/1.73 m² [95% CI, -2.7 to 0.0 mL/min/1.73 m²] in children and -0.9 mL/min/1.73 m² [CI, -1.2 to -0.5 mL/min/1.73 m²] in adults) across the FAS (2 to 90 years) and SCr range (40 to 490 µmol/L [0.45 to 5.54 mg/dL]) and with fewer estimation errors exceeding 30% (6.5% [CI, 3.8% to 9.1%] in children and 3.1% [CI, 2.5% to 3.6%] in adults) compared with the CKiD and CKD-EPI equations.

LIMITATION

No Black patients were included.

CONCLUSION

The new EKFC equation shows improved accuracy and precision compared with commonly used equations for estimating GFR from SCr levels.

PRIMARY FUNDING SOURCE

Swedish Research Council (Vetenskapsrådet).

Incidence of fractures in middle-aged individuals with early chronic kidney disease: a population-based analysis of CARTaGENE

BACKGROUND

Previous studies evaluating fractures in chronic kidney disease (CKD) have mostly focused on hip or major fractures in aged populations with moderate to advanced CKD. We aimed at evaluating the association between early CKD and fracture incidence at all sites across age and sex in middle-aged individuals.

METHODS

We analyzed CARTaGENE, a prospective population-based survey of 40- to 69-year-old individuals from Quebec (Canada). Estimated glomerular filtration rate (eGFR) at baseline was evaluated categorically or continuously using restricted cubic splines. Fractures at any site (except toes, hand and craniofacial) for up to 7 years of follow-up were identified through administrative databases using a validated algorithm. Adjusted Cox models were used to evaluate the association of CKD with fracture. Interaction terms for age and sex were also added.

RESULTS

A total of 19 391 individuals (756 CKD Stage 3; 9114 Stage 2; 9521 non-CKD) were included and 829 fractures occurred during a median follow-up of 70 months. Compared with the median eGFR of 90 mL/min/1.73 m2, eGFRs of ≤60 mL/min/1.73 m2 were associated with increased fracture incidence in unadjusted and adjusted models [adjusted hazard ratio (HR) = 1.25 (95% confidence interval 1.05-1.49) for 60 mL/min/1.73 m2; 1.65 (1.14-2.37) for 45 mL/min/1.73 m2]. The eGFR was linearly associated with fracture incidence <75 mL/min/1.73 m2 [HR = 1.18 (1.04-1.34) per 10 mL/min/1.73 m2 decrease] but not above [HR = 0.98 (0.91-1.06) per 10 mL/min/1.73 m2 decrease). The effect of decreased eGFR on fracture incidence was more pronounced in younger individuals [HR = 2.45 (1.28-4.67) at 45 years; 1.11 (0.73-1.67) at 65 years] and in men.

CONCLUSIONS

Even early CKD increases fracture incidence, especially in younger individuals and in men.

Aging is associated with slower renal progression in patients with chronic kidney disease

Objectives:

Chronic kidney disease (CKD) is prevalent among the elderly. However, little is known about how the clinical course of CKD vary with age. The purpose of this study was to examine the impact of aging on the risk of end-stage kidney disease (ESKD) in patients with moderate to advanced CKD.

Materials and Methods:

A total of 454 patients with stages 3–5 CKD were prospectively followed for a median of 5.1 years. The primary outcome was ESKD needing chronic dialysis therapy or preemptive kidney transplantation. The secondary outcome was a composite of ESKD or all-cause mortality.

Results:

The mean age of the patients was 65 ± 13 years. 65.4% were men, 44.9% had diabetes mellitus, and 22.7% had cardiovascular disease. Overall, 142 participants progressed to ESKD and 63 participants died. Compared with young patients (age <65 years, n = 205), elderly patients (age ≥65 years, n = 249) were associated with a significantly decreased risk of ESKD in Cox proportional hazards models adjusted for sex, smoking history, diabetes mellitus, cardiovascular disease, systolic blood pressure, estimated glomerular filtration rate, urine protein: Creatinine ratio, use of renin-angiotensin-aldosterone blocker, hemoglobin, phosphate, interleukin-6, body mass index, and N-terminal pro-brain natriuretic peptide (hazard ratio [HR]: 0.66; 95% confidence interval [CI]: 0.45, 0.96; P = 0.028). The results remained statistically significant when death as a competing risk was taken into account (subdistribution HR: 0.65; 95% CI: 0.45, 0.95, P = 0.026). Notably, elderly did not predict a higher risk for the composite outcome (HR: 0.94; 95% CI: 0.67, 1.32; P = 0.723).

Conclusion:

Elderly confers a decreased risk of ESKD in Taiwanese patients with moderate to advanced CKD. Our findings suggest that age is an important effect modifier for CKD progression.

The case for early identification and intervention of chronic kidney disease: conclusions from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference

Chronic kidney disease (CKD) causes substantial global morbidity and increases cardiovascular and all-cause mortality. Unlike other chronic diseases with established strategies for screening, there has been no consensus on whether health systems and governments should prioritize early identification and intervention for CKD. Guidelines on evaluating and managing early CKD are available but have not been universally adopted in the absence of incentives or quality measures for prioritizing CKD care. The burden of CKD falls disproportionately upon persons with lower socioeconomic status, who have a higher prevalence of CKD, limited access to treatment, and poorer outcomes. Therefore, identifying and treating CKD at the earliest stages is an equity imperative. In 2019, Kidney Disease: Improving Global Outcomes (KDIGO) held a controversies conference entitled "Early Identification and Intervention in CKD." Participants identified strategies for screening, risk stratification, and treatment for early CKD and the key health system and economic factors for implementing these processes. A consensus emerged that CKD screening coupled with risk stratification and treatment should be implemented immediately for high-risk persons and that this should ideally occur in primary or community care settings with tailoring to the local context.

Familial Aggregation of CKD and Heritability of Kidney Biomarkers in the General Population: The Lifelines Cohort Study

RATIONALE & OBJECTIVE

Chronic kidney disease (CKD) has a heritable component. We aimed to quantify familial aggregation of CKD in the general population and assess the extent to which kidney traits could be explained by genetic and environmental factors.

STUDY DESIGN

Cross-sectional 3-generation family study.

SETTING & PARTICIPANTS

Data were collected at entry into the Lifelines Cohort Study from a sample of the general population of the northern Netherlands, composed predominantly of individuals of European ancestry.

EXPOSURE

Family history of CKD.

OUTCOMES

The primary outcome was CKD, defined as estimated glomerular filtration rate (eGFR)<60mL/min/1.73m², where GFR was estimated using the CKD Epidemiology Collaboration creatinine equation. Among a subsample for which urinary albumin concentration was available (n=59,943), urinary albumin excretion was expressed as the rate of urinary albumin excretion (UAE) per 24 hours or urinary albumin-creatinine ratio (UACR).

ANALYTICAL APPROACH

Familial aggregation of CKD was assessed by calculating the recurrence risk ratio (RRR), using adapted Cox proportional hazards models. Heritability of continuous kidney-related traits was estimated using linear mixed models and defined as the ratio of the additive genetic variance to total phenotypic variance. All models were adjusted for age, sex, and known risk factors for kidney disease.

RESULTS

Among 155,911 participants with available eGFR data, the prevalence of CKD was 1.19% (1,862 cases per 155,911). The risk of CKD in those with an affected first-degree relative was 3 timeshigher than the risk in the total sample (RRR, 3.04 [95% CI, 2.26-4.09). In those with an affected spouse, risk of CKD was also higher (RRR, 1.56 [95% CI, 1.20-1.96]), indicative of shared environmental factors and/or assortative mating. Heritability estimates of eGFR, UAE, and UACR were 44%, 20%, and 18%, respectively. For serum urea, creatinine, and uric acid, estimates were 31%, 37%, and 48%, respectively, whereas estimates for serum electrolytes ranged from 22% to 28%.

LIMITATIONS

Use of estimated rather than measured GFR. UAE data only available in a subsample.

CONCLUSIONS

In this large population-based family study, a positive family history was strongly associated with increased risk of CKD. We observed moderate to high heritability of kidney traits and related biomarkers. These results indicate an important role of genetic factors in CKD risk.

SGLT2 inhibition requires reconsideration of fundamental paradigms in chronic kidney disease, 'diabetic nephropathy', IgA nephropathy and podocytopathies with FSGS lesions

In 2020, the Dapagliflozin and Prevention of Adverse Outcomes in Chronic Kidney Disease (DAPA-CKD) trial first demonstrated that inhibition of the sodium-glucose transporter-2 (SGLT2) with dapagliflozin attenuates the progression of chronic kidney disease (CKD) with proteinuria in patients with or without diabetes at an unprecedented effect size. These results have far-reaching implications for a series of traditional concepts in Nephrology. It now became obvious that CKD with and without diabetes involves a predominant SGLT2-driven pathophysiology compared with the other pathogenic pathways currently under consideration. As SGLT2 inhibition is similarly efficacious in diabetic and non-diabetic CKD with proteinuria, treating CKD rather than 'diabetic nephropathy' becomes the central paradigm. Indeed, in older adults with type 2 diabetes, CKD is rather of multifactorial origin. As the DAPA-CKD trial included more patients with immunoglobulin A nephropathy (IgAN) than any of the previous IgAN trials, dual renin-angiotensin/SGLT2 inhibition may become the new standard. The same applies for patients with podocytopathy-related focal segmental glomerulosclerosis lesions. From now on, IgAN and podocytopathy trials without SGLT2 inhibition as background therapy and without glomerular filtration rate decline as primary outcome criterion will be of limited value. These and other potential implications will trigger broad discussions and secondary research activities with conclusions difficult to predict today. However, one is for sure: Nephrology after the DAPA-CKD trial will be not the same as it was before. Finally!

Kidney Function as Risk Factor and Predictor of Cardiovascular Outcomes and Mortality Among Older Adults

RATIONALE & OBJECTIVE

Estimated glomerular filtration rate (eGFR) and urinary albumin-creatinine ratio (UACR) are associated with cardiovascular events in the general population but their utility among older adults is unclear. We investigated the associations of eGFR and UACR with stroke, myocardial infarction (MI), and death among older adults.

STUDY DESIGN

Population-based cohort study.

SETTING & PARTICIPANTS

1,581 participants (aged≥70 years) in the Berlin Initiative Study (BIS) without prior stroke or MI.

EXPOSURES & PREDICTORS

Serum creatinine- and cystatin C-based eGFR, UACR categories, and measured GFR (n=436).

OUTCOMES

Stroke, MI, and all-cause mortality.

ANALYTICAL APPROACH

HRs and 95% CIs derived from multivariable-adjusted Cox proportional hazards models for association analyses. Net reclassification improvement (NRI) and C statistic differences comparing the predictive benefit of kidney measures with a traditional cardiovascular risk model.

RESULTS

During a median follow-up of 8.2 years, 193 strokes, 125 MIs, and 531 deaths occurred. Independent of UACR, when GFR was estimated using the creatinine- and cystatin C-based BIS equation, eGFR of 45 to 59mL/min/1.73m² (vs eGFR>60mL/min/1.73m²) was associated with stroke (HR, 2.23; 95% CI, 1.55-3.21) but not MI or all-cause mortality. For those with eGFR<45mL/min/1.73m², the HRs were 1.99 (95% CI, 1.23-3.20) for stroke, 1.38 (95% CI, 0.81-2.36) for MI, and 1.57 (95% CI, 1.20-2.06) for mortality. Compared with UACR<30mg/g, UACR of 30 to 300mg/g was not associated with stroke (HR, 0.91; 95% CI, 0.63-1.33) but was associated with MI (HR, 1.65; 95% CI, 1.09-2.51) and all-cause mortality (HR, 1.63; 95% CI, 1.34-1.98). Prediction analysis for stroke showed significant positive NRI for eGFR calculated using the cystatin C-based Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation and the creatinine- and cystatin C-based BIS and Full Age Spectrum equations. UACR demonstrated significant positive NRIs for MI and mortality.

LIMITATIONS

eGFR and UACR categorization based on single assessments; lack of cause-specific death data.

CONCLUSIONS

eGFR of 45 to 59mL/min/1.73m² without albuminuria was associated with stroke but not MI or all-cause mortality in older adults. In contrast, UACR of 30 to 300mg/g was associated with MI and all-cause mortality but not with stroke. Furthermore, cystatin C-based eGFR improved risk prediction for stroke in this cohort of older adults.

How to interpret an estimated glomerular filtration rate (eGFR) in 2020?

Chronic kidney disease (CKD) is defined as abnormalities of kidney structure and function proven to be chronic. The prevalence of CKD in the majority of studies is 10%-16%, neglecting the chronicity character. Jonsson et al., in a nationwide study defining CKD adhering strictly to Kidney Disease: Improving Global Outcomes (KDIGO) criteria, found a clearly lower prevalence of CKD (6%). This indicated that to obtain a correct CKD prevalence, one should start by correctly applying the KDIGO guidelines.

Breath Ammonia Is a Useful Biomarker Predicting Kidney Function in Chronic Kidney Disease Patients

Chronic kidney disease (CKD) is a public health problem and its prevalence has increased worldwide; patients are commonly unaware of the condition. The present study aimed to investigate whether exhaled breath ammonia via vertical-channel organic semiconductor (V-OSC) sensor measurement could be used for rapid CKD screening. We enrolled 121 CKD stage 1–5 patients, including 19 stage 1 patients, 26 stage 2 patients, 38 stage 3 patients, 21 stage 4 patients, and 17 stage 5 patients, from July 2019 to January 2020. Demographic and laboratory data were recorded. The exhaled ammonia was collected and rapidly measured by the V-OSC sensor to correlate with kidney function. Results showed no significant difference in age, sex, body weight, hemoglobin, albumin level, and comorbidities in different CKD stage patients. Correlation analysis demonstrated a good correlation between breath ammonia and blood urea nitrogen levels, serum creatinine levels, and estimated glomerular filtration rate (eGFR). Breath ammonia concentration was significantly elevated with increased CKD stage compared with the previous stage (CKD stage 1/2/3/4/5: 636 ± 94; 1020 ± 120; 1943 ± 326; 4421 ± 1042; 12781 ± 1807 ppb, p < 0.05). The receiver operating characteristic curve analysis showed an area under the curve (AUC) of 0.835 (p < 0.0001) for distinguishing CKD stage 1 from other CKD stages at 974 ppb (sensitivity, 69%; specificity, 95%). The AUC was 0.831 (p < 0.0001) for distinguishing between patients with/without eGFR < 60 mL/min/1.73 m² (cutoff 1187 ppb: sensitivity, 71%; specificity, 78%). At 886 ppb, the sensitivity increased to 80% but the specificity decreased to 69%. This value is suitable for kidney function screening. Breath ammonia detection with V-OSC is a real time, inexpensive, and easy to administer measurement device for screening CKD with reliable diagnostic accuracy.

Phosphate and Kidney Healthy Aging

<b><i>Background:</i></b> The aging population is increasing rapidly, much faster than our understanding on how to promote healthy aging free of multimorbidities. The aging kidney shows a decline in its function. Whether this decline is preventable or physiological is still debated. Main risks factors for developing CKD are aging common comorbidites, such as hypertension, diabetes, and obesity. Phosphate is vital for our organism, but it is also present in a great variety of food products as food additive and preservative. Due to the higher consumption of processed food in the last century, concern has arisen if a chronic high consumption of phosphate may be toxic impacting on healthy aging. <b><i>Summary:</i></b> Several studies show an association between higher serum phosphate levels and a higher risk of overall mortality and cardiovascular disease. Moreover, higher phosphate levels also worsen CKD progression and may contribute to renal dysfunction in healthy individuals. Acute high phosphate intake is rare but can cause acute kidney injury. Yet, the question if controlling phosphate intake may modulate serum phosphate concentrations remains unanswered, as assessment of phosphate intake is still a difficult task. Phosphate consumption estimations by dietary recalls are largely underestimated, especially in populations groups consuming high amount of processed food. <b><i>Key Message:</i></b> A healthy diet with phosphate source from food may contribute to promote healthy aging and longevity.

Chronic Kidney Disease in Tasmania: Protocol for a Data Linkage Study

Background

Chronic kidney disease (CKD) is a significant and growing health burden globally. Tasmania has the highest state prevalence for non-Indigenous Australians and it has consistently had the lowest incidence and prevalence of dialysis in Australia.

Objective

To examine the gap between the high community prevalence of CKD in Tasmania and the low use of dialysis.

Methods

This is a retrospective cohort study using linked data from 5 health and 2 pathology data sets from the island state of Tasmania, Australia. The study population consists of any person (all ages including children) who had a blood measurement of creatinine with the included pathology providers between January 1, 2004, and December 31, 2017. This study population (N=460,737) includes within it a CKD cohort, which was detected via pathology or documentation of kidney replacement therapy (KRT; dialysis or kidney transplant). Kidney function (estimated glomerular filtration rate [eGFR]) was calculated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula. Individuals with 2 measures of eGFR<60 mL/min/1.73 m², at least 90 days apart, were identified as having CKD and were included in the CKD cohort. Individuals treated with dialysis or transplant were identified from the Australia and New Zealand Dialysis and Transplant Registry.

Results

The study population consisted of 460,737 people (n=245,573 [53.30%] female, mean age 47.4 years) who were Tasmanian residents aged 18 years and older and were followed for a median of 7.8 years. During the later 5 years of the study period, 86.79% (355,622/409,729) of Tasmanian adults were represented. The CKD cohort consisted of 56,438 people (ie, 12.25% of the study population; 53.87% (30,405/56,438) female, mean age 69.9 years) followed for a median of 10.4 years with 56,039 detected via eGFR and 399 people detected via documentation of KRT. Approximately half (227,433/460,737, 49.36%) of the study population and the majority of the CKD cohort (41,448/56,438, 73.44%) had an admission episode. Of the 55,366 deaths recorded in the study population, 45.10% (24,970/55,366) had CKD.

Conclusions

Whole-of-population approaches to examine CKD in the community can be achieved by data linkage. Over this 14-year period, CKD affected 12.25% (56,438/460,737) of Tasmanian adult residents and was present in 45.10% (24,970/55,366) of deaths.

International Registered Report Identifier (IRRID)

DERR1-10.2196/20160

Prevalence, concordance and associations of chronic kidney disease by five estimators in South Africa

Background

To determine the prevalence, distribution, concordance and associations of chronic kidney disease (CKD) determined by five glomerular filtration rate (GFR) formulae in urban black residents of Cape Town.

Methods

Data collection in this cross-sectional study included interviews, clinical measurements and biochemical analyses, including serum creatinine and cystatin C levels. GFR was based on the CKD Epidemiology Collaboration (CKD-EPI) equations (CKD-EPI creatinine (CKD-EPIcr), CKD-EPI cystatin C (CKD-EPIcys), CKD-EPI creatinine-cystatins (CKD-EPIcr-cys)), Modification of Diet in Renal Disease (MDRD) and Cockcroft-Gault formula (CGF). GFR < 60 mL/min/1.73 m² defined CKD.

Results

Among 392 men and 700 women, mean GFR, was between 114.0 (CKD-EPIcr) and 135.4 mL/min/1.73 m² (CGF) in men, and between 107.5 (CKD-EPIcr-cys) and 173.4 mL/min/1.73 m² (CGF) in women. CKD prevalence ranged from 2.3% (CKD-EPIcr and MDRD) to 5.1% (CKD-EPIcys) in men and 1.6% (CGF) to 6.7% (CKD-EPIcr-cys) in women. The kappa statistic was high between CKD-EPIcr and MDRD (0.934), and CKD-EPIcys and CKD-EPIcr-cys (0.815), but fair-to-moderate between the other eqs. (0.353–0.565). In the basic regressions, older age and body mass index ≥30 kg/m², but not gender, were significantly associated with CKD-EPIcr-defined CKD. In the presence of these three variables, hypertension, heart rate ≥ 90 beats/minute, diabetes and low-density lipoprotein cholesterol were significant predictors of prevalent CKD.

Conclusions

Varying CKD prevalence estimates, because of different GFR equations used, underscores the need to improve accuracy of CKD diagnoses. Furthermore, screening for CKD should be incorporated into the routine assessment of high-risk patients such as those with hypertension or diabetes.

CKD Awareness Among US Adults by Future Risk of Kidney Failure

RATIONALE & OBJECTIVE

Persons with chronic kidney disease (CKD) are often unaware of their disease status. Efforts to improve CKD awareness may be most effective if focused on persons at highest risk for progression to kidney failure.

STUDY DESIGN

Serial cross-sectional surveys.

SETTING & PARTICIPANTS

Nonpregnant adults (aged≥20 years) with CKD glomerular filtration rate categories 3-4 (G3-G4) who participated in the National Health and Nutrition Examination Survey from 1999 to 2016 (n = 3,713).

PREDICTOR

5-year kidney failure risk, estimated using the Kidney Failure Risk Equation. Predicted risk was categorized as minimal (<2%), low (2%-<5%), intermediate (5%-<15%), or high (≥15%).

OUTCOME

CKD awareness, defined by answering "yes" to the question "Have you ever been told by a doctor or other health professional that you had weak or failing kidneys?"

ANALYTICAL APPROACH

Prevalence of CKD awareness was estimated within each risk group using complex sample survey methods. Associations between Kidney Failure Risk Equation risk and CKD awareness were assessed using multivariable logistic regression. CKD awareness was compared with awareness of hypertension and diabetes during the same period.

RESULTS

In 2011 to 2016, unadjusted CKD awareness was 9.6%, 22.6%, 44.7%, and 49.0% in the minimal-, low-, intermediate-, and high-risk groups, respectively. In adjusted analyses, these proportions did not change over time. Awareness of CKD, including among the highest risk group, remains consistently below that of hypertension and diabetes and awareness of these conditions increased over time.

LIMITATIONS

Imperfect sensitivity of the "weak or failing kidneys" question for ascertaining CKD awareness.

CONCLUSIONS

Among adults with CKD G3-G4 who have 5-year estimated risks for kidney failure of 5%-<15% and≥15%, approximately half were unaware of their kidney disease, a gap that has persisted nearly 2 decades.

The prevalence of chronic kidney disease in Iceland according to KDIGO criteria and age-adapted estimated glomerular filtration rate thresholds

Most epidemiological studies on chronic kidney disease (CKD) are based solely on estimated glomerular filtration rate (eGFR). Few studies have included proteinuria, while the chronicity criterion is usually omitted. To explore this, we examined the prevalence of CKD stages 1-5 in Iceland based on multiple markers of kidney damage. All serum creatinine values, urine protein measurements and diagnostic codes for kidney diseases and comorbid conditions for people aged 18 years and older were obtained from electronic medical records of all healthcare institutions in Iceland in 2008-2016. CKD was defined according to the Kidney Disease: Improving Global Outcomes (KDIGO) clinical practice guideline using diagnoses indicative of a chronic kidney disease, proteinuria and/or an eGFR under 60 mL/min/1.73 m² for over three months. Mean annual age-standardized prevalence of CKD stages 1-5 was calculated based on the KDIGO criteria and age-adapted eGFR thresholds from 2,120,147 creatinine values for 218,437 individuals, 306,531 proteinuria measurements for 86,364 individuals and 6973 individuals carrying a kidney disease diagnosis. Median age was 63 years (range, 18-106) and 47% were male. The mean annual age standardized CKD prevalence was 5.13% for men and 6.75% for women using the KDIGO criteria but by age-adapted eGFR cut-offs, the prevalence was 3.27% for men and 4.01% for women. Thus, our nationwide study, defining CKD in Iceland with strict adherence to the KDIGO criteria, demonstrates a lower prevalence of CKD than anticipated from most previous studies.

Treatment switch in Fabry disease- a matter of dose?

BACKGROUND

Patients with Fabry disease (FD) on reduced dose of agalsidase-beta or after switch to agalsidase-alfa show a decline in chronic kidney disease epidemiology collaboration-based estimated glomerular filtration rate (eGFR) and a worsened plasma lyso-Gb3 decrease. Hence, the most effective dose is still a matter of debate.

METHODS

In this prospective observational study, we assessed end-organ damage and clinical symptoms in 78 patients who had received agalsidase-beta (1.0 mg/kg) for >1 year, which were assigned to continue this treatment (agalsidase-beta, regular-dose group, n=17); received a reduced dose of agalsidase-beta and subsequent switch to agalsidase-alfa (0.2 mg/kg) or a direct switch to 0.2 mg/kg agalsidase-alfa (switch group, n=22); or were re-switched to agalsidase-beta after receiving agalsidase-alfa for 12 months (re-switch group, n=39) with a follow-up of 88±25 months.

RESULTS

No differences for clinical events were observed for all groups. Patients within the re-switch group started with the worst eGFR values at baseline (p=0.0217). Overall, eGFR values remained stable in the regular-dose group (p=0.1052) and decreased significantly in the re-switch and switch groups (p<0.0001 and p=0.0052, respectively). However, in all groups males presented with an annual loss of eGFR by -2.9, -2.5 and -3.9 mL/min/1.73 m² (regular-dose, re-switch, switch groups, all p<0.05). In females, eGFR decreased significantly only in the re-switch group by -2.9 mL/min/1.73 m² per year (p<0.01). Lyso-Gb3 decreased in the re-switch group after a change back to agalsidase-beta (p<0.05).

CONCLUSIONS

Our data suggest that a re-switch to high dosage of agalsidase results in a better biochemical response, but not in a significant renal amelioration especially in classical males.

GFR in Healthy Aging: an Individual Participant Data Meta-Analysis of Iohexol Clearance in European Population-Based Cohorts

BACKGROUND

Population mean GFR is lower in older age, but it is unknown whether healthy aging is associated with preserved rather than lower GFR in some individuals.

METHODS

We investigated the cross-sectional association between measured GFR, age, and health in persons aged 50-97 years in the general population through a meta-analysis of iohexol clearance measurements in three large European population-based cohorts. We defined a healthy person as having no major chronic disease or risk factors for CKD and all others as unhealthy. We used a generalized additive model to study GFR distribution by age according to health status.

RESULTS

There were 935 (22%) GFR measurements in persons who were healthy and 3274 (78%) in persons who were unhealthy. The mean GFR was lower in older age by -0.72 ml/min per 1.73 m² per year (95% confidence interval [95% CI], -0.96 to -0.48) for men who were healthy versus -1.03 ml/min per 1.73 m² per year (95% CI, -1.25 to -0.80) for men who were unhealthy, and by -0.92 ml/min per 1.73 m² per year (95% CI, -1.14 to -0.70) for women who were healthy versus -1.22 ml/min per 1.73 m² per year (95% CI, -1.43 to -1.02) for women who were unhealthy. For healthy and unhealthy people of both sexes, both the 97.5th and 2.5th GFR percentiles exhibited a negative linear association with age.

CONCLUSIONS

Healthy aging is associated with a higher mean GFR compared with unhealthy aging. However, both the mean and 97.5 percentiles of the GFR distribution are lower in older persons who are healthy than in middle-aged persons who are healthy. This suggests that healthy aging is not associated with preserved GFR in old age.

Longitudinal Changes in Kidney Function Estimated from Cystatin C and Its Association with Mortality in Elderly Women

BACKGROUND/AIMS

Prospective data on age-related changes in kidney function are required, especially since the current Kidney Disease Improving Global Outcomes (KDIGO) definition has been suggested to classify a large number of elderly people with CKD.

OBJECTIVE

This study, a complement to our previous Cr-based study in the same cohort, is aimed at evaluating cystatin C (cysC)-based changes in kidney function during aging in older women and analyzing the association between CKD and mortality through 10 years of follow-up.

METHODS

cysC was available in 981 women from the Osteoporosis Prospective Risk Assessment (OPRA) cohort, all aged 75 years on entry. Reinvestigations were made after 5 (n = 685) and 10 years (n = 365). Kidney function was estimated (estimated glomerular filtration rate [eGFR]) using Chronic Kidney Disease Epidemiology Collaboration cysC and Caucasian, Asian, Pediatric, and Adult cysC equations and the change in function calculated. Women were staged equivalent to CKD stage 1, 2, 3a, or 3b-5 according to the KDIGO classification. Mortality risk was estimated for 5-year or 10-year follow-up time using Cox proportional hazard analyses (reference category, CKD stages 1 and 2).

RESULTS

Mortality risk for women with the worst kidney function (CKD stages 3b-5) increased during both 5-year follow-up times compared to that for women in stages 1 and 2 (age 75-80 years: adjusted Hazard Ratio [HRadj] 3.9, 95% confidence interval [CI] 2.3-6.5; age 80-85 years: HRadj 1.7, 95% CI 1.0-2.7). In contrast, women in stage 3a had increased risk only in the first 5-year follow-up (HRadj 1.7, 95% CI 1.0-3.0, age 75-80 years). Change in kidney function amounted to a loss of 1.9 (±1.4) mL/min/1.73 m2 per year during the 10-year follow-up, and at age 85 years, 4 of every 5 women had an eGFR equivalent to CKD.

CONCLUSION

In the future, an age-adapted definition of CKD, lowering the threshold for CKD in the elderly, may be beneficial to avoid overdiagnosis of CKD.

Inflammaging and Complement System: A Link Between Acute Kidney Injury and Chronic Graft Damage

The aberrant activation of complement system in several kidney diseases suggests that this pillar of innate immunity has a critical role in the pathophysiology of renal damage of different etiologies. A growing body of experimental evidence indicates that complement activation contributes to the pathogenesis of acute kidney injury (AKI) such as delayed graft function (DGF) in transplant patients. AKI is characterized by the rapid loss of the kidney's excretory function and is a complex syndrome currently lacking a specific medical treatment to arrest or attenuate progression in chronic kidney disease (CKD). Recent evidence suggests that independently from the initial trigger (i.e., sepsis or ischemia/reperfusions injury), an episode of AKI is strongly associated with an increased risk of subsequent CKD. The AKI-to-CKD transition may involve a wide range of mechanisms including scar-forming myofibroblasts generated from different sources, microvascular rarefaction, mitochondrial dysfunction, or cell cycle arrest by the involvement of epigenetic, gene, and protein alterations leading to common final signaling pathways [i.e., transforming growth factor beta (TGF-β), p16 ink4a , Wnt/β-catenin pathway] involved in renal aging. Research in recent years has revealed that several stressors or complications such as rejection after renal transplantation can lead to accelerated renal aging with detrimental effects with the establishment of chronic proinflammatory cellular phenotypes within the kidney. Despite a greater understanding of these mechanisms, the role of complement system in the context of the AKI-to-CKD transition and renal inflammaging is still poorly explored. The purpose of this review is to summarize recent findings describing the role of complement in AKI-to-CKD transition. We will also address how and when complement inhibitors might be used to prevent AKI and CKD progression, therefore improving graft function.

Sex- and age-specific variations, temporal trends and metabolic determinants of serum uric acid concentrations in a large population-based Austrian cohort

Little is known about sex- and age-specific variations and temporal trends in serum uric acid (SUA) concentrations, the prevalence of hyperuricemia and its association with metabolic risk factors in the general population. Between January 1, 1985 and June 30, 2005 146,873 participants (42% women) were recruited. Prevalence of hyperuricemia was estimated applying a common (SUA > 360 µmol/L) and sex-specific cut-off points (women > 340 µmol/L, men > 420 µmol/L). At baseline, mean age was 41.2 years in men and 51.5 years in women, mean SUA concentration was 314.8 µmol/L and 243.6 µmol/L, respectively. Applying a common cut-off point, the prevalence of hyperuricemia was 18.5% in men and 4.4% in women and by sex-specific cut-off points it was 15.1% and 13.8%, respectively. SUA levels increased by 6.7 µmol/L per decade in men, but remained constant in women until the age of 50 years with a sharp increase by approximately 22 µmol/L per decade thereafter. In men and women, hyperuricemia was associated with obesity, hypertriglyceridemia and elevated gamma-glutamyl transferase. With increasing age SUA levels and the prevalence of hyperuricemia rise in a sex-specific manner. Above the age of 65 years, the sex-specific prevalence of hyperuricemia in women outreaches that in men.

Therapeutic management of HIV-infected patients with chronic kidney disease

CKD and HIV infection are two chronic diseases impacting heavily on the survival of the affected patients. The interplay between HIV infection and chronic kidney disease (CKD) is complex and interactions occur at multiple levels. Approach to the management of HIV-infected patients requires special attention to face the numerous therapeutic difficulties ranging from drug-drug interactions to drug-toxicity. The most effective strategy is targeted to suppression of HIV viral load, as it dramatically changes the prognosis of the patients as well as prevents the development of HIV-associated kidney disease. As shown in this review, the approach to the therapeutic management of CKD in the setting of HIV infection varies in relation to the degree of renal impairment.