Proteinuria and rate of change in kidney function in a community-based population

Pre-admission proteinuria impacts risk of non-recovery after dialysis-requiring acute kidney injury

Renal recovery after dialysis-requiring acute kidney injury (AKI-D) is an important clinical and patient-centered outcome. Here we examined whether the pre-admission proteinuria level independently influences risk for non-recovery after AKI-D in a community-based population. All adult members of Kaiser Permanente Northern California who experienced AKI-D between January 1, 2009 and September 30, 2015 were included. Pre-admission proteinuria levels were determined by dipstick up to four years before the AKI-D hospitalization and the outcome was renal recovery (survival and dialysis-independence four weeks and more) at 90 days after initiation of renal replacement therapy. We used multivariable logistic regression to adjust for baseline estimated glomerular filtration rate (eGFR), age, sex, ethnicity, short-term predicted risk of death, comorbidities, and medication use. Among 5,347 adults with AKI-D, the mean age was 66 years, 59% were men, and 50% were white. Compared with negative/trace proteinuria, the adjusted odds ratios for non-recovery (continued dialysis-dependence or death) were 1.47 (95% confidence interval 1.19-1.82) for 1+ proteinuria and 1.92 (1.54-2.38) for 2+ or more proteinuria. Among survivors, the crude probability of recovery ranged from 83% for negative/trace proteinuria with baseline eGFR over 60 mL/min/1.73m² to 25% for 2+ or more proteinuria with eGFR 15-29 mL/min/1.73m². Thus, the pre-AKI-D level of proteinuria is a graded, independent risk factor for non-recovery and helps to improve short-term risk stratification for patients with AKI-D.

Changes in proteinuria and the risk of myocardial infarction in people with diabetes or pre-diabetes: a prospective cohort study

Background

The relationship between changes in proteinuria and myocardial infarction (MI) remains unclear in people with diabetes or pre-diabetes. We aimed to evaluate the predictive value and independent role of changes in proteinuria over a 2-year period in the incidence of MI in people with diabetes or pre-diabetes.

Methods

Based on the baseline and 2-year dipstick screening results from the Kailuan prospective cohort study, participants were divided into four categories: no proteinuria, remittent proteinuria, incident proteinuria, and persistent proteinuria. Four multivariable Cox proportional hazard models were built to adjust for the effects of different confounding covariates.

Results

Among the 17,625 participants in this study, there were a total of 238 incidents of MI during a median follow-up of 6.69 years. After adjusting for demography factors and laboratory indices, the association between persistent proteinuria and MI incidence was maintained (hazard ratio [HR] 2.50, 95% confidence interval [CI] 1.48–4.22). Every decrease of proteinuria from 2006 to 2008 was observed to be responsible for a 21% decline of MI incidence (HR 0.79, 95% CI 0.68–0.90). The interaction between changes in proteinuria and diabetes was confirmed with no effect on MI (P = 0.3371).

Conclusions

Persistent proteinuria is an independent risk factor for MI incidence in the pre-diabetic and diabetic population. These findings may help clinicians to interpret proteinuria changes in the outpatient setting and provide possible preventive approaches for people with pre-diabetes or diabetes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-017-0586-7) contains supplementary material, which is available to authorized users.

Treatment decisions for older adults with advanced chronic kidney disease

Dialysis initiation rates among older adults, aged 75 years or greater, are increasing at a faster rate than for younger age groups. Older adults with advanced CKD (eGFR < 30 ml/min/1.73 m2) typically lose renal function slowly, often suffer from significant comorbidity and thus may die from associated comorbidities before they require dialysis.A patient's pattern of renal function loss over time in relation to their underlying comorbidities can serve as a guide to the probability of a future dialysis requirement. Most who start dialysis, initiate treatment "early", at an estimated glomerulofiltration rate (eGFR) >10 ml/min/1.73 m2 and many initiate dialysis in hospital, often in association with an episode of acute renal failure. In the US older adults start dialysis at a mean e GFR of 12.6 ml/min/1.73 m2 and 20.6% die within six months of dialysis initiation. In both the acute in hospital and outpatient settings, many older adults appear to be initiating dialysis for non-specific, non-life threatening symptoms and clinical contexts. Observational data suggests that dialysis does not provide a survival benefit for older adults with poor mobility and high levels of comorbidity. To optimize the care of this population, early and repeat shared decision making conversations by health care providers, patients, and their families should consider the risks, burdens, and benefits of dialysis versus conservative management, as well as the patient specific symptoms and clinical situations that could justify dialysis initiation. The potential advantages and disadvantages of dialysis therapy should be considered in conjunction with each patient's unique goals and priorities.In conclusion, when considering the morbidity and quality of life impact associated with dialysis, many older adults may prefer to delay dialysis until there is a definitive indication or may opt for conservative management without dialysis. This approach can incorporate all CKD treatments other than dialysis, provide psychosocial and spiritual support and active symptom management and may also incorporate a palliative care approach with less medical monitoring of lab parameters and more focus on the use of drug therapies directed to relief of a patient's symptoms.

Time-Varying Association of Individual BP Components with eGFR in Late-Stage CKD

BACKGROUND AND OBJECTIVES

The association of individual BP components with changes in eGFR in patients with late-stage CKD is unknown. The objectives of our study were to examine the associations of systolic BP, diastolic BP, and pulse pressure with continuous temporal changes in eGFR and an eGFR decline ≥30% in late-stage CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We performed a retrospective cohort study (2010-2015) of patients with CKD in a multidisciplinary CKD clinic with an eGFR≤30. The associations of repeat measures of BP (systolic BP, diastolic BP, and pulse pressure) with eGFR were examined using general linear mixed models. The associations of BP components and eGFR decline ≥30% were examined with time-varying Cox models.

RESULTS

In total, 1203 patients were followed for a median of 548 days (interquartile range, 292-913), with an average of 6.7 visits and BP measures per patient. Mean baseline systolic BP, diastolic BP, pulse pressure, and eGFR were 139.2 mmHg, 73.2 mmHg, 64.9 mmHg, and 16.8 ml/min, respectively. Systolic BP and diastolic BP measures over time were statistically significantly associated with changes in eGFR (P<0.001), whereas pulse pressure was not. Patients with extremes of systolic BP (<105 or >170) and high diastolic BP (>90) measures were at a higher risk of GFR decline ≥30% (systolic BP <105: hazard ratio, 1.51; 95% confidence interval, 0.98 to 2.34; systolic BP >170: hazard ratio, 1.62; 95% confidence interval, 1.05 to 2.49; referent systolic BP =121-130; diastolic BP =81-90: hazard ratio, 1.40; 95% confidence interval, 0.99 to 1.86; diastolic BP >90: hazard ratio, 1.83; 95% confidence interval, 1.21 to 2.77; referent diastolic BP =61-70). The findings were consistent after multiple sensitivity analyses. Pulse pressure was not significantly associated with risk of eGFR decline.

CONCLUSIONS

In patients referred to a multidisciplinary care clinic with late-stage CKD, only extremes of systolic BP and elevations of diastolic BP were associated with eGFR decline.

Absence of Decline of Kidney Function in Human Immunodeficiency Virus-Infected Patients Under Routine Clinical Management

BACKGROUND

Since the introduction of antiretroviral therapy (ART), human immunodeficiency virus (HIV)-infected patients have a drastically improved prognosis but at the same time they are also more affected by non-HIV related complications, such as chronic kidney disease. The objective of our study was to investigate the effect of proteinuria and tenofovir (TDF)-containing ART regimens on the temporal evolution of estimated glomerular filtration rate (eGFR).

METHODS

Between April 2008 and October 2012, we enrolled 395 patients with a complete renal evaluation among patients from the ANRS C03 Aquitaine cohort, a prospective hospital-based cohort of HIV-1-infected patients under routine clinical management in southwestern France. eGFR was estimated at each patient follow-up visit. A linear mixed model was used to analyze eGFR dynamics, accounting for change in TDF by modeling eGFR trajectory according to treatment periods.

RESULTS

At inclusion, 56.7% of patients were treated with TDF-containing ART regimens; prevalence of glomerular and tubular proteinuria was 7.9 and 10.8% respectively. A 1-year increase of cumulative exposure to TDF was significantly associated with a mean eGFR decrease of 1.27 mL/min/1.73 m2 (95% CI [-2.14 to -0.41]). Only a urine protein to creatinine ratio >100 mg/mmol and/or a urine albumin to creatinine ratio >70 mg/mmol were associated with eGFR trajectory (mean slope 6.18 mL/min/1.73 m2 per year; 95% CI [2.71 to 9.65]), whereas TDF use was not associated with such eGFR temporal evolution.

CONCLUSION

Decline in kidney function is limited under routine clinical management with monitoring of renal function and interventions including decision to continue or discontinue TDF.

Proteinuria as a Therapeutic Target in Advanced Chronic Kidney Disease: a Retrospective Multicenter Cohort Study

Current evidence of proteinuria reduction as a surrogate target in advanced chronic kidney disease (CKD) is incomplete due to lack of patient-pooled database. We retrospectively studied a multicenter cohort of 1891 patients who were enrolled in the nationwide multidisciplinary pre-end stage renal disease care program with a baseline glomerular filtration rate (GFR) <45 mL/min/1.73 m(2) and followed longitudinally to investigate the effect of the change in proteinuria on renal death (defined as composite of dialysis and death occurring before initiation of dialysis). The group with a change in proteinuria ≤0.30 g/g (n = 1261) had lower cumulative probabilities of renal death (p < 0.001). In a linear regression model, a higher baseline proteinuria and a greater increase in proteinuria were associated with faster annual GFR decline. Cox's analysis showed that every 1 unit increase in natural log(baseline proteinuria, 10 g/g) and every 0.1 g/g increase in the change in proteinuria resulted in 67% (HR = 1.67, 95% CI: 1.46-1.91) and 1% (HR = 1.01, 95% CI: 1.01-1.01) greater risk of renal death respectively after adjusting for the effects of the other covariates. Our study provided a patient-based evidence to support proteinuria as a therapeutic target in advanced CKD.

CKD Progression and Mortality among Hispanics and Non-Hispanics

Although recommended approaches to CKD management are achieved less often in Hispanics than in non-Hispanics, whether long-term outcomes differ between these groups is unclear. In a prospective longitudinal analysis of participants enrolled into the Chronic Renal Insufficiency Cohort (CRIC) and Hispanic-CRIC Studies, we used Cox proportional hazards models to determine the association between race/ethnicity, CKD progression (50% eGFR loss or incident ESRD), incident ESRD, and all-cause mortality, and linear mixed-effects models to assess differences in eGFR slope. Among 3785 participants, 13% were Hispanic, 43% were non-Hispanic white (NHW), and 44% were non-Hispanic black (NHB). Over a median follow-up of 5.1 years for Hispanics and 6.8 years for non-Hispanics, 27.6% of all participants had CKD progression, 21.3% reached incident ESRD, and 18.3% died. Hispanics had significantly higher rates of CKD progression, incident ESRD, and mean annual decline in eGFR than did NHW (P<0.05) but not NHB. Hispanics had a mortality rate similar to that of NHW but lower than that of NHB (P<0.05). In adjusted analyses, the risk of CKD progression did not differ between Hispanics and NHW or NHB. However, among nondiabetic participants, compared with NHB, Hispanics had a lower risk of CKD progression (hazard ratio, 0.61; 95% confidence interval, 0.39 to 0.95) and incident ESRD (hazard ratio, 0.50; 95% confidence interval, 0.30 to 0.84). At higher levels of urine protein, Hispanics had a significantly lower risk of mortality than did non-Hispanics (P<0.05). Thus, important differences in CKD progression and mortality exist between Hispanics and non-Hispanics and may be affected by proteinuria and diabetes.

Renal function trajectory over time and adverse clinical outcomes

The growing burden of chronic kidney disease (CKD), with its associated morbidity and mortality, is recognized as a major public health problem globally and causing substantial load on health care systems. The current framework for the definition and staging of CKD, based on eGFR levels or presence of kidney damage, is useful for clinical classification of patients, but identifies a huge number of people as having CKD which is too many to target for intervention. The ability to identify a subset of patients, at high risk for adverse outcomes, would be useful to inform clinical management. The current staging system applies static definitions of kidney function that fail to capture the dynamic nature of the kidney disease over time. Now-a-days, it is possible to capture multiple measurements of different laboratory test results for an individual including eGFR values. A new possibility for identifying individuals at higher risk of adverse outcomes is being explored through assessment and consideration of the rate of change in kidney function over time, and this approach will be feasible in the current context of digitalization of health record keeping system. On the basis of the existing evidence, this paper summarizes important findings that support the concept of dynamic changes in kidney function over time, and discusses how the magnitude of these changes affect the future adverse outcomes of kidney disease, particularly the End Stage Renal Disease (ESRD), CVD and mortality.

NF-κB-dependent increase in tissue factor expression is responsible for hypoxic podocyte injury

BACKGROUND

Fibrin deposition within glomeruli is commonly seen in kidney biopsy specimens, suggesting enhanced coagulant activity. Tissue factor (TF) is a coagulation factor which is also related to various biological effects, and TF is upregulated by hypoxia in cancer cells. Recently, hypoxic podocyte injury has been proposed, therefore, we investigated TF expression in hypoxia.

METHODS

Conditionally immortalized human podocytes were differentiated and treated under hypoxic or normoxic conditions. mRNA expressions of TF and tissue factor pathway inhibitor (TFPI) were analyzed by quantitative RT-PCR. Protein levels of TF and TFPI were tested by enzyme-linked immunosorbent assay. We employed small interfering RNA (siRNA) to temporary knockdown early growth response protein 1 (Egr-1), hypoxia-inducible factor-1α (HIF-1α) and TF. The expression of CD2-associated protein (CD2AP) mRNA and phalloidin staining was examined to assess podocyte injury.

RESULTS

Hypoxia increased mRNA expression of TF (6 h: 2.3 ± 0.05 fold, p < 0.001, 24 h: 5.6 ± 2.4 fold, p < 0.05) and suppressed TFPI (6 h: 0.54 ± 0.04 fold, p < 0.05, 24 h: 0.24 ± 0.06 fold, p < 0.001) compared with normoxia. Similarly, protein levels of TF were increased and TFPI were decreased. Egr-1 siRNA did not change TF mRNA expression. Pyrrolidine dithiocarbamate (PDTC), a nuclear factor kappa B (NF-κB) inhibitor, significantly reduced hypoxia induced TF expression, and HIF-1α knockdown further increased TF. Hypoxia resulted in decreased CD2AP and actin reorganization in podocytes, and these changes were attenuated by TF siRNA.

CONCLUSION

Hypoxia increased the expression of TF in human podocytes NF-κB dependently. TF may have a critical role in the hypoxic podocyte injury.

Natural history and outcome of light chain deposition disease

Light chain deposition disease (LCDD) is characterized by the deposition of monotypic immunoglobulin light chains in the kidney, resulting in renal dysfunction. Fifty-three patients with biopsy-proven LCDD were prospectively followed at the UK National Amyloidosis Center. Median age at diagnosis was 56 years, and patients were followed for a median of 6.2 years (range, 1.1-14.0 years). Median renal survival from diagnosis by Kaplan-Meier analysis was 5.4 years, and median estimated patient survival was 14.0 years; 64% of patients were alive at censor. Sixty-two percent of patients required dialysis, and median survival from commencement of dialysis was 5.2 years. There was a strong association between hematologic response to chemotherapy and renal outcome, with a mean improvement in glomerular filtration rate (GFR) of 6.1 mL/min/year among those achieving a complete or very good partial hematologic response (VGPR) with chemotherapy, most of whom remained dialysis independent, compared with a mean GFR loss of 6.5 mL/min/year among those achieving only a partial or no hematologic response (P < .009), most of whom developed end-stage renal disease (ESRD; P = .005). Seven patients received a renal transplant, and among those whose underlying clonal disorder was in sustained remission, there was no recurrence of LCDD up to 9.7 years later. This study highlights the need to diagnose and treat LCDD early and to target at least a hematologic VGPR with chemotherapy, even among patients with advanced renal dysfunction, to delay progression to ESRD and prevent recurrence of LCDD in the renal allografts of those who subsequently receive a kidney transplant.

Risks for mortality and renal replacement therapy in atherosclerotic renovascular disease compared with other causes of chronic kidney disease

AIM

Patients with atherosclerotic renovascular disease (ARVD) have an increased risk for death and likelihood of initiating renal replacement therapy (RRT) compared with the general population. No data exist to describe prognosis in ARVD compared with other causes of chronic kidney disease (CKD). We compare patient outcomes between ARVD and other causes of CKD.

METHODS

Patients were selected from two prospective observational cohort studies of outcome in ARVD and CKD. Multivariate Cox regression was used to compare risk for RRT and death (both prior to and following initiation of RRT) between patients with ARVD and other causes of CKD.

RESULTS

Of 1472 patients (563 (38%) ARVD, 909 (62%) non-ARVD), 242 (16%) progressed to RRT and 640 (44%) died over a median follow-up period of 4.1 (2.4-5.6) years. Patients with ARVD had an increased risk for death (HR 1.5 (1.2-1.8), P < 0.001) but not for RRT (HR 1.0 (0.7-1.4), P = 0.9). The largest increase in risk for death was observed relative to renal limited diseases, e.g. pyelonephritis (HR 2.4 (1.3-4.5), P = 0.004) and interstitial/infiltrative disease (HR 2.2 (1.3-4.5), P = 0.02). Following initiation of RRT, patients with ARVD had a significantly increased risk for death compared with patients without ARVD (HR 3.3 (2.2-5.0), P < 0.001).

CONCLUSIONS

Patients with ARVD as a cause of CKD have an increased risk for death both prior to and following initiation of RRT. Further work should seek to identify modifiable risk factors relevant to prognosis.

Glomerular Density in Biopsy-Proven Hypertensive Nephrosclerosis

BACKGROUND

Previous autopsy studies suggested that a reduced nephron number is associated with increased risk of hypertension and chronic kidney disease. However, the significance of the nephron number estimated from a renal biopsy in patients with hypertensive nephrosclerosis (HNS) has not yet been elucidated.

METHODS

In this cross-sectional study, we examined the clinicopathological findings of biopsy-proven HNS patients with preserved renal function (estimated glomerular filtration rate ≥ 60 ml/min/1.73 m(2)). The glomerular density (GD; the number of glomeruli per total renal cortical area) in biopsy specimens was evaluated as a surrogate of the nephron number. Renal biopsies from kidney transplant donors were used as healthy controls.

RESULTS

A total of 58 HNS patients were enrolled. The GD value in the HNS patients was low compared with those in the kidney transplant donors (2.0 vs. 3.2 /mm(2)). These differences remained significant when globally sclerotic glomeruli were included in the calculation of the GD. Of note, the GD in HNS patients with overt proteinuria (≥1 g/day) was significantly lower than that of HNS patients with mild proteinuria (<1g/day; 1.8 vs. 2.2/mm(2), P = 0.014). In contrast, other histopathological parameters, including the severity of global glomerulosclerosis, interstitial fibrosis/tubular atrophy and arterial and arteriole lesions were comparable between the 2 HNS subgroups. In addition, the GD was identified as a factor that was associated with the amount of urinary protein excretion at biopsy, independent of other clinicopathological factors.

CONCLUSIONS

These results suggest that a low GD is a renal histological characteristic of HNS patients, especially those with overt proteinuria.

Estimated glomerular filtration rate progression in UK primary care patients with type 2 diabetes and diabetic kidney disease: a retrospective cohort study

AIMS

To examine the rates of diabetic kidney disease (DKD) progression and associated factors, we undertook a study of estimated glomerular filtration rate (eGFR) in a historical cohort of UK primary care patients with type 2 diabetes mellitus (T2DM) and associated DKD from the Clinical Practice Research Datalink.

METHODS

Our eligible population were patients with definitive T2DM from a recorded diagnostic code with either a diagnosis of chronic kidney disease (CKD) or renal function test values and renal abnormalities consistent with a CKD diagnosis, identified between 1 October 2006 and 31 December 2011. Only patients with albuminuria results reported in mg/l were used for the longitudinal statistical analyses of the eGFR rate of change using multilevel models.

RESULTS

We identified 111,030 patients with T2DM. Among them 58.6% (95% confidence interval (CI): 58.3-58.9) had CKD and 37.2% (95% CI: 36.9-37.5%) had presumed DKD at baseline. Only 19.4% of patients had urinary albumin test results expressed as mg/l in the year prior to index date. Almost two-thirds (63.8%) of patients with T2DM and presumed DKD received prescriptions for angiotensin-converting enzyme (ACE) inhibitors or angiotensin type 1 receptor blockers (ARB) or both. Time-dependent variables that predict subsequent eGFR decline include increased albuminuria, time from index date and older age.

CONCLUSION

Only a minority of diabetic patients with DKD had quantitative albuminuria assessments. The relatively low proportion of DKD patients with ACEi or ARB prescriptions suggests a gap between healthcare practice and available scientific evidence during the study period. Increased albuminuria and older age were the most consistent predictors of subsequent eGFR decline.

Early chronic kidney disease: diagnosis, management and models of care

Chronic kidney disease (CKD) is prevalent in many countries, and the costs associated with the care of patients with end-stage renal disease (ESRD) are estimated to exceed US$1 trillion globally. The clinical and economic rationale for the design of timely and appropriate health system responses to limit the progression of CKD to ESRD is clear. Clinical care might improve if early-stage CKD with risk of progression to ESRD is differentiated from early-stage CKD that is unlikely to advance. The diagnostic tests that are currently used for CKD exhibit key limitations; therefore, additional research is required to increase awareness of the risk factors for CKD progression. Systems modelling can be used to evaluate the impact of different care models on CKD outcomes and costs. The US Indian Health Service has demonstrated that an integrated, system-wide approach can produce notable benefits on cardiovascular and renal health outcomes. Economic and clinical improvements might, therefore, be possible if CKD is reconceptualized as a part of primary care. This Review discusses which early CKD interventions are appropriate, the optimum time to provide clinical care, and the most suitable model of care to adopt.

Predictors of Rapid Progression of Glomerular and Nonglomerular Kidney Disease in Children and Adolescents: The Chronic Kidney Disease in Children (CKiD) Cohort

BACKGROUND

Few studies have prospectively evaluated the progression of chronic kidney disease (CKD) in children and adolescents, as well as factors associated with progression.

STUDY DESIGN

Prospective multicenter observational cohort study.

SETTING & PARTICIPANTS

496 children and adolescents with CKD enrolled in the Chronic Kidney Disease in Children (CKiD) Study.

PREDICTORS

Proteinuria, hypoalbuminemia, blood pressure, dyslipidemia, and anemia.

OUTCOMES

Parametric failure-time models were used to characterize adjusted associations between baseline levels and changes in predictors and time to a composite event of renal replacement therapy or 50% decline in glomerular filtration rate (GFR).

RESULTS

398 patients had nonglomerular disease and 98 had glomerular disease; of these, 29% and 41%, respectively, progressed to the composite event after median follow-ups of 5.2 and 3.7 years, respectively. Demographic and clinical characteristics and outcomes differed substantially according to the underlying diagnosis; hence, risk factors for progression were assessed in stratified analyses, and formal interactions by diagnosis were performed. Among patients with nonglomerular disease and after adjusting for baseline GFR, times to the composite event were significantly shorter with urinary protein-creatinine ratio > 2mg/mg, hypoalbuminemia, elevated blood pressure, dyslipidemia, male sex, and anemia, by 79%, 69%, 38%, 40%, 38%, and 45%, respectively. Among patients with glomerular disease, urinary protein-creatinine ratio >2mg/mg, hypoalbuminemia, and elevated blood pressure were associated with significantly reduced times to the composite event by 94%, 71%, and 67%, respectively. Variables expressing change in patient clinical status over the initial year of the study contributed significantly to the model, which was cross-validated internally.

LIMITATIONS

Small number of events in glomerular patients and use of internal cross-validation.

CONCLUSIONS

Characterization and modeling of risk factors for CKD progression can be used to predict the extent to which these factors, either alone or in combination, would shorten the time to renal replacement therapy or 50% decline in GFR in children with CKD.

Interplay of vitamin D, erythropoiesis, and the renin-angiotensin system

For many years deficiency of vitamin D was merely identified and assimilated to the presence of bone rickets. It is now clear that suboptimal vitamin D status may be correlated with several disorders and that the expression of 1-α-hydroxylase in tissues other than the kidney is widespread and of clinical relevance. Recently, evidence has been collected to suggest that, beyond the traditional involvement in mineral metabolism, vitamin D may interact with other kidney hormones such as renin and erythropoietin. This interaction would be responsible for some of the systemic and renal effects evoked for the therapy with vitamin D. The administration of analogues of vitamin D has been associated with an improvement of anaemia and reduction in ESA requirements. Moreover, vitamin D deficiency could contribute to an inappropriately activated or unsuppressed RAS, as a mechanism for progression of CKD and/or cardiovascular disease. Experimental data on the anti-RAS and anti-inflammatory effects treatment with active vitamin D analogues suggest a therapeutic option particularly in proteinuric CKD patients. This option should be considered for those subjects that are intolerant to anti-RAS agents or, as add-on therapy, in those already treated with anti-RAS but not reaching the safe threshold level of proteinuria.

Serum 25-hydroxyvitamin D level and kidney function decline in a Swiss general adult population

BACKGROUND AND OBJECTIVES

Molecular evidence suggests that levels of vitamin D are associated with kidney function loss. Still, population-based studies are limited and few have considered the potential confounding effect of baseline kidney function. This study evaluated the association of serum 25-hydroxyvitamin D with change in eGFR, rapid eGFR decline, and incidence of CKD and albuminuria.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Baseline (2003-2006) and 5.5-year follow-up data from a Swiss adult general population were used to evaluate the association of serum 25-hydroxyvitamin D with change in eGFR, rapid eGFR decline (annual loss >3 ml/min per 1.73 m(2)), and incidence of CKD and albuminuria. Serum 25-hydroxyvitamin D was measured at baseline using liquid chromatography-tandem mass spectrometry. eGFR and albuminuria were collected at baseline and follow-up. Multivariate linear and logistic regression models were used considering potential confounding factors.

RESULTS

Among the 4280 people included in the analysis, the mean±SD annual eGFR change was -0.57±1.78 ml/min per 1.73 m(2), and 287 (6.7%) participants presented rapid eGFR decline. Before adjustment for baseline eGFR, baseline 25-hydroxyvitamin D level was associated with both mean annual eGFR change and risk of rapid eGFR decline, independently of baseline albuminuria. Once adjusted for baseline eGFR, associations were no longer significant. For every 10 ng/ml higher baseline 25-hydroxyvitamin D, the adjusted mean annual eGFR change was -0.005 ml/min per 1.73 m(2) (95% confidence interval, -0.063 to 0.053; P=0.87) and the risk of rapid eGFR decline was null (odds ratio, 0.93; 95% confidence interval, 0.79 to 1.08; P=0.33). Baseline 25-hydroxyvitamin D level was not associated with incidence of CKD or albuminuria.

CONCLUSIONS

The association of 25-hydroxyvitamin D with eGFR decline is confounded by baseline eGFR. Sufficient 25-hydroxyvitamin D levels do not seem to protect from eGFR decline independently from baseline eGFR.

Resolution of low-grade proteinuria is associated with improved outcomes after renal transplantation-a retrospective longitudinal study

Low-grade proteinuria and systolic hypertension (SHT) are risk factors for allograft failure. Both are dynamic variables and their relationship is not independent. We have simultaneously analyzed the effects of proteinuria and SHT on graft outcomes in 805 adult Kidney Transplant Recipients and impact of their changes over time. Proteinuria and systolic blood pressure (SBP) were recorded for years 1 and 3 posttransplantation. Subjects with proteinuria >1 g/day were excluded. Patients were divided into groups based on proteinuria (Absent(A) <150 mg/day or low-grade(P)150 mg-1 g/day) and blood pressure (Normotensive-SBP <140 mmHg or hypertensive-SBP ≥ 140 mmHg). Graft survival was assessed in all four groups over 10 years by multivariate analysis. At the three annual time points (Year 1, 2 and 3) hypertensive patients with proteinuria had the worst graft survival. Patients with persistent proteinuria between years 1-2 and 2-3 had the poorest graft survival with an improvement if proteinuria regressed (P-A), especially in the Hypertensive group. The impact of proteinuria was highest in persistently hypertensive patients between years 1-3. Thus both proteinuria and SHT were associated with poor graft survival and the combination of the two led to the worst outcomes. Importantly, SHT was associated with significantly worse outcomes in patients with proteinuria. Patient cohort with SHT and low-grade proteinuria represent a selective group that might benefit from intervention.

Vitamin D analogues to target residual proteinuria: potential impact on cardiorenal outcomes

Residual proteinuria, the amount of proteinuria that remains during optimally dosed renin-angiotensin-aldosterone system (RAAS) blockade, is an independent risk factor for progressive renal function loss and cardiovascular complications in chronic kidney disease (CKD) patients. Dual RAAS blockade may reduce residual proteinuria but without translating into improved cardiorenal outcomes at least in diabetic nephropathy; rather, dual RAAS blockade may increase the risk of adverse events. These findings have challenged the concept of residual proteinuria as an absolute treatment target. Therefore, new strategies must be explored to address whether by further reduction of residual proteinuria using interventions not primarily targeting the RAAS benefit in terms of cardiorenal risk reduction would accrue. Both clinical and experimental intervention studies have demonstrated that vitamin D can reduce residual proteinuria through both RAAS-dependent and RAAS-independent pathways. Future research should prospectively explore vitamin D treatment as an adjunct to RAAS blockade in an interventional trial exploring clinically relevant cardiorenal end points.

Compliance Index, a Marker of Peripheral Arterial Stiffness, may Predict Renal Function Decline in Patients with Chronic Kidney Disease

BACKGROUND

Compliance index derived from digital volume pulse (CI-DVP), measuring the relationship between volume and pressure changes in fingertip, is a surrogate marker of peripheral arterial stiffness. This study investigated if CI-DVP can predict renal function deterioration, cardiovascular events and mortality in patients with chronic kidney disease (CKD).

METHODS

In this prospective observational study, 149 CKD patients were included for final analysis. CI-DVP and brachial-ankle pulse wave velocity (baPWV) were measured, decline in renal function was assessed by the estimated glomerular filtration rate (eGFR) slope. Composite renal and cardiovascular outcomes were evaluated, including ≥50% eGFR decline, start of renal replacement therapy, and major adverse events.

RESULTS

Patients in CKD stages 3b to 5 had higher baPWV and lower CI-DVP values than those in patients with CKD stages 1 to 3a. Stepwise multivariate linear regression analysis showed that lower CI-DVP (p =0.0001) and greater proteinuria (p =0.0023) were independent determinants of higher eGFR decline rate. Multivariate Cox regression analysis revealed that CI-DVP (HR 0.68, 95% CI 0.46-1.00), baseline eGFR (HR 0.96, 95% CI 0.94-0.98) and serum albumin (HR 0.17, 95% CI 0.07-0.42) were independent predictors for composite renal and cardiovascular outcomes.

CONCLUSIONS

Compliance index, CI-DVP, was significantly associated with renal function decline in patients with CKD. A higher CI-DVP may have independent prognostic value in slower renal function decline and better composite renal and cardiovascular outcomes in CKD patients.

Evidence-based decision-making 6: Utilization of administrative databases for health services research

Health-care systems require reliable information on which to base health-care planning and make decisions, as well as to evaluate their policy impact. Administrative data provide important information about health services use, expenditures, clinical outcomes, and may be used to assess quality of care. With increased digitalization and accessibility of administrative databases, these data are more readily available for health service research purposes, aiding evidence-based decision-making. This chapter discusses the utility of administrative data for population-based studies of health and health care.

Kidney function, albuminuria and life expectancy

BACKGROUND

Lower estimated glomerular filtration rate is associated with reduced life expectancy. Whether this association is modified by the presence or absence of albuminuria, another cardinal finding of chronic kidney disease, is unknown.

OBJECTIVE

Our objective was to estimate the life expectancy of middle-aged men and women with varying levels of eGFR and concomitant albuminuria.

DESIGN

A retrospective cohort study.

SETTING

A large population-based cohort identified from the provincial laboratory registry in Alberta, Canada.

PARTICIPANTS

Adults aged ≥30 years who had outpatient measures of serum creatinine and albuminuria between May 1, 2002 and March 31, 2008.

MEASUREMENTS

PREDICTOR

Baseline levels of kidney function identified from serum creatinine and albuminuria measurements.

OUTCOMES

all cause mortality during the follow-up.

METHODS

Patients were categorized based on their estimated glomerular filtration rate (eGFR) (≥60, 45-59, 30-44, and 15-29 mL/min/1 · 73 m(2)) as well as albuminuria (normal, mild, and heavy) measured by albumin-to-creatinine ratio or urine dipstick. The abridged life table method was applied to calculate the life expectancies of men and women from age 40 to 80 years across combined eGFR and albuminuria categories. We also categorized participants by severity of kidney disease (low risk, moderately increased risk, high risk, and very high risk) using the combination of eGFR and albuminuria levels.

RESULTS

Among men aged 50 years and with eGFR ≥60 mL/min/1.73 m(2), estimated life expectancy was 24.8 (95% CI: 24.6-25.0), 17.5 (95% CI: 17.1-17.9), and 13.5 (95% CI: 12.6-14.3) years for participants with normal, mild and heavy albuminuria respectively. Life expectancy for men with mild and heavy albuminuria was 7.3 (95% CI: 6.9-7.8) and 11.3 (95% CI: 10.5-12.2) years shorter than men with normal proteinuria, respectively. A reduction in life expectancy was associated with an increasing severity of kidney disease; 24.8 years for low risk (95% CI: 24.6-25.0), 19.1 years for moderately increased risk (95% CI: 18.7-19.5), 14.2 years for high risk (95% CI: 13.5-15.0), and 9.6 years for very high risk (95% CI: 8.4-10.8). Among women of similar age and kidney function, estimated life expectancy was 28.9 (95% CI: 28.7-29.1), 19.8 (95% CI: 19.2-20.3), and 14.8 (95% CI: 13.5-16.0) years for participants with normal, mild and heavy albuminuria respectively. Life expectancy for women with mild and heavy albuminuria was 9.1 (95% CI: 8.5-9.7) and 14.2 (95% CI: 12.9-15.4) years shorter than the women with normal proteinuria, respectively. For women also a graded reduction in life expectancy was observed across the increasing severity of kidney disease; 28.9 years for low risk (95% CI: 28.7-29.1), 22.5 years for moderately increased risk (95% CI: 22.0-22.9), 16.5 years for high risk (95% CI: 15.4-17.5), and 9.2 years for very high risk (95% CI: 7.8-10.7).

LIMITATIONS

Possible misclassification of long-term kidney function categories cannot be eliminated. Possibility of confounding due to concomitant comorbidities cannot be ruled out.

CONCLUSION

The presence and degree of albuminuria was associated with lower estimated life expectancy for both gender and was especially notable in those with eGFR ≥30 mL/min/1.73 m(2). Life expectancy associated with a given level of eGFR differs substantially based on the presence and severity of albuminuria.

Dietary restriction in moderately obese rats improves body size and glucose handling without the renal and hepatic alterations observed with a high-protein diet

Obesity is increasing worldwide, and high-protein (HP) diets are widely used for weight loss. However, the overall safety of HP diets is not well established in obese individuals, who make up a significant proportion of the population. To evaluate the health effects of an HP diet in obesity, obesity-prone (OP) Sprague-Dawley rats were given high-fat diets for 12 weeks to induce obesity. Following this, for 8 more weeks, these rats were given either a normal-protein (NP) (15% of energy) or an HP (35% of energy) diet ad libitum, or the NP diet at a restricted level to achieve body weights similar to those of the HP group (pair-weighted (PW) group). Obesity-resistant (OR) control rats were also given the NP diet throughout the feeding period. The HP-OP group had higher food intake but lower body weight, improved glucose handling, and lowered serum haptoglobin compared with the NP-OP group. These benefits were also observed in PW-OP rats. In addition, PW-OP rats had less fat accumulation when compared with NP-OP rats, and an improved Lee index, lower liver size, and lower serum alanine aminotransferase when compared with HP-OP rats. On the other hand, kidney size, proteinuria, and serum homocysteine were increased in HP-OP rats compared with NP-OP rats, whereas PW-OP rats did not experience these effects. These results indicate that in obese rats, more benefits are obtained via dietary restriction with an NP diet and without some of the potentially detrimental effects of an HP diet.

Presence of early CKD-related metabolic complications predict progression of stage 3 CKD: a case-controlled study

BACKGROUND

Only a subset of patients who enter stage 3 chronic kidney disease (CKD) progress to stage 4. Identifying which patients entering stage 3 are most likely to progress could improve outcomes, by allowing more appropriate referrals for specialist care, and spare those unlikely to progress the adverse effects and costliness of an unnecessarily aggressive approach. We hypothesized that compared to non-progressors, patients who enter stage 3 CKD and ultimately progress have experienced greater loss of renal function, manifested by impairment of metabolic function (anemia, worsening acidosis and mineral abnormalities), than is reflected in the eGFR at entry to stage 3. The purpose of this case-controlled study was to design a prediction model for CKD progression using laboratory values reflecting metabolic status.

METHODS

Using data extracted from the electronic health record (EHR), two cohorts of patients in stage 3 were identified: progressors (eGFR declined >3 ml/min/1.73 m2/year; n=117) and non-progressors (eGFR declined <1 ml/min/1.713 m2; n=364). Initial laboratory values recorded a year before to a year after the time of entry to stage 3, reflecting metabolic complications (hemoglobin, bicarbonate, calcium, phosphorous, and albumin) were obtained. Average values in progressors and non-progressors were compared. Classification algorithms (Naïve Bayes and Logistic Regression) were used to develop prediction models of progression based on the initial lab data.

RESULTS

At the entry to stage 3 CKD, hemoglobin, bicarbonate, calcium, and albumin values were significantly lower and phosphate values significantly higher in progressors compared to non-progressors even though initial eGFR values were similar. The differences were sufficiently large that a prediction model of progression could be developed based on these values. Post-test probability of progression in patients classified as progressors or non-progressors were 81% (73% - 86%) and 17% (13% - 23%), respectively.

CONCLUSIONS

Our studies demonstrate that patients who enter stage 3 and ultimately progress to stage 4 manifest a greater degree of metabolic complications than those who remain stable at the onset of stage 3 when eGFR values are equivalent. Lab values (hemoglobin, bicarbonate, phosphorous, calcium and albumin) are sufficiently different between the two cohorts that a reasonably accurate predictive model can be developed.

Risk of ESRD and death in patients with CKD not referred to a nephrologist: a 7-year prospective study

BACKGROUND AND OBJECTIVES

Rising prevalence of CKD requires active involvement of general practitioners to limit ESRD and mortality risk. However, the outcomes of patients with CKD exclusively managed by general practitioners are ill defined.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We prospectively evaluated 30,326 adult patients with nondialysis CKD stages 1-5 who had never received consultation in tertiary nephrology care recruited from 700 general practitioner offices in Italy during 2002 and 2003. CKD stages were classified as stages 1 and 2 (GFR ≥ 60 ml/min per 1.73 m(2) and either albuminuria or an International Classification of Diseases, Ninth Revision, Clinical Modification code for kidney disease), stage 3a (GFR=59-45), stage 3b (GFR=44-30), stage 4 (GFR=29-15), and stage 5 (GFR<15). Primary outcome was the risk of ESRD (dialysis or transplantation) or all-cause death.

RESULTS

Overall 64% of patients were in stage 3a, and 4.5% of patients were in stages 3b-5. Patients with stages 1 and 2 were younger, were predominantly men, more frequently had diabetes, and had lower prevalence of previous cardiovascular disease than patients with stages 3a-5. Hypertension was frequent in all CKD stages (80%-94%), whereas there was a lower prevalence of dyslipidemia, albuminuria, and obesity associated with more advanced CKD. During the follow-up (median=7.2 years; interquartile range=4.7-7.7), 6592 patients died and 295 started ESRD. Compared with stages 1 and 2 (reference), mortality risk (hazard ratio, 95% confidence interval) was higher in stages 3b-5 (1.66, 1.49-1.86, 2.75, 2.41-3.13 and 2.54, 2.01-3.22, respectively) but not stage 3a (1.11, 0.99-1.23). Similarly, ESRD risk (hazard ratio, 95% confidence interval) was not higher at stage 3a (1.44, 0.79-2.64) but was greater in stages 3b-5 (11.0, 6.3-19.5, 91.2, 53.2-156.2 and, 122.8, 67.9-222.0, respectively). Among modifiable risk factors, anemia and albuminuria significantly predicted either outcome, whereas hypertension only predicted mortality.

CONCLUSIONS

In patients with CKD not referred to nephrology, risks of ESRD and mortality were higher in those with CKD stages 3b-5.

Differences in susceptibility to develop parameters of diabetic nephropathy in four mouse strains with type 1 diabetes

One-third of diabetes mellitus patients develop diabetic nephropathy, and with underlying mechanisms unknown it is imperative that diabetic animal models resemble human disease. The present study investigated the susceptibility to develop diabetic nephropathy in four commonly used and commercially available mouse strains with type 1 diabetes to determine the suitability of each strain. Type 1 diabetes was induced in C57Bl/6, NMRI, BALB/c, and 129Sv mice by alloxan, and conscious glomerular filtration rate, proteinuria, and oxidative stress levels were measured in control and diabetic animals at baseline and after 5 and 10 wk. Histological alterations were analyzed using periodic acid-Schiff staining. Diabetic C57Bl/6 displayed increased glomerular filtration rate, i.e., hyperfiltration, whereas all other parameters remained unchanged. Diabetic NMRI developed the most pronounced hyperfiltration as well as increased oxidative stress and proteinuria but without glomerular damage. Diabetic BALB/c did not develop hyperfiltration but presented with pronounced proteinuria, increased oxidative stress, and glomerular damage. Diabetic 129Sv displayed proteinuria and increased oxidative stress without glomerular hyperfiltration or damage. However, all strains displayed intrastrain correlation between oxidative stress and proteinuria. In conclusion, diabetic C57Bl/6 and NMRI both developed glomerular hyperfiltration but neither presented with histological damage, although NMRI developed low-degree proteinuria. Thus these strains may be suitable when investigating the mechanism causing hyperfiltration. Neither BALB/c nor 129Sv developed hyperfiltration although both developed pronounced proteinuria. However, only BALB/c developed detectable histological damage. Thus BALB/c may be suitable when studying the roles of proteinuria and histological alterations for the progression of diabetic nephropathy.