Chronic kidney disease the promise and the perils

Chronic kidney disease in the elderly and frail patient: perspectives with opinions and comments

Chronic kidney disease is common in elderly and frail people. The importance of age in staging chronic kidney disease is discussed as well as the possible constraints of staging what is actually a 'continuum' of disease progression. Frailty is a biological state characterized by the decline of several physiological systems and strongly correlated with adverse health outcomes, including mortality. Frailty is measured by the Comprehensive Geriatric Assessment, which focuses on quantitative rating scales that determine not only the clinical profile and pathological risk of frail individuals, but also their residual capacities, functional status, and quality of life. There is circumstantial evidence that Comprehensive Geriatric Assessment can improve both survival and quality of life in elderly chronic kidney disease patients. Despite the long list of emerging risk factors and markers of chronic kidney disease progression, it is the authors' opinion that a single biochemical parameter can hardly cover the complexity of chronic kidney disease in elderly and frail patients. Among the numerous clinical scores proposed, the European Renal Best Practice guidelines recommend the Renal Epidemiology and Information Network score and the Kidney Failure Risk Equations. The former provides a reasonable estimate of short-term mortality risk, the latter provides the risk of chronic kidney disease progression. In conclusion, the elderly individual with advanced chronic kidney disease is often comorbid and frail with peculiarities in terms of disease grading, clinical assessment and monitoring. The time has come to reshape the care of this growing number of patients by focusing on multidisciplinary teams both in the hospital and in the community.

Association of elevated blood serum high-sensitivity C-reactive protein levels and body composition with chronic kidney disease: A population-based study in Taiwan

Chronic kidney disease (CKD) is a risk factor for cardiovascular diseases and is associated with an increase in all-cause mortality. Studies regarding association among various body compositions in different inflamed states and the risk of CKD were rare. We aimed to evaluate the relationship among body composition, high-sensitivity C-reactive protein (hsCRP) level, and the risk of CKD.This was a retrospective cross-sectional study using annual health examination data from 2 medical centers in northern and southern Taiwan between January and December 2015. We performed a variance analysis of the estimated glomerular filtration rate (eGFR) distribution in groups based on hsCRP and body fat percentage (BFP), and a multivariate logistic regression model was used to assess the relationship among BFP, hsCRP levels, and CKD.A total of 10,267 subjects aged ≥18 years undergoing health examination were analyzed. In our study, overweight/obese patients were associated with increased risk of CKD. Nevertheless, in subjects with elevated hsCRP level, overweight/obese group with a higher BFP had a lower risk of CKD as compared with overweight/obese with normal BFP group (for BMI ≧ 23 kg/m, high BFP/high hsCRP: odds ratio [OR] for CKD 1.86, 95% confidence interval [CI] = 1.10-3.17, P = .02; normal BFP/high hsCRP group: OR 2.32, 95% CI = 1.23-4.37, P = .01) after adjusting for various confounders.Our findings suggest that various body compositions in different inflamed states may interfere with the risk of CKD. These results provide an important method for the early detection of impaired renal function by identifying various body compositions and inflammation states to detect CKD at an earlier stage.

Combined body mass index with high-sensitivity C-reactive protein as independent predictors for chronic kidney disease in a relatively healthy population in Taiwan

BACKGROUND/OBJECTIVES

Obesity, a chronic inflammatory state, increases risk of cardiovascular disease and insulin resistance, which are the leading cause of end-stage renal disease (ESRD). We evaluated the relationship between body mass index (BMI) and high-sensitivity C-reactive protein (hsCRP) level and impaired kidney function to determine the predictive value of both markers for estimating chronic kidney disease (CKD) risk in a healthy adult population in Taiwan.

SUBJECTS/METHODS

In a retrospective cross-sectional study of 4100 subjects ⩾18 years, a multivariate logistic regression model was used to assess the relationship among BMI, high hsCRP levels and CKD. Receiver-operating characteristic curve and Youden index were developed to define the discrimination power of combining BMI with hsCRP for CKD prediction and to determine the best predictive index.

RESULTS

Overweight/obese subjects with high hsCRP levels had the highest odds ratio for CKD (P=0.048). In females, combining BMI with hsCRP for CKD prediction was superior to that of males (0.890 vs 0.623, respectively; both P<0.001). For females, the Youden index was 25.65 kg/m(2) for BMI and 1.04 μg/ml for hsCRP.

CONCLUSIONS

Overweight/obesity with higher hsCRP levels is associated with reduced renal function and increased risk for CKD. BMI and hsCRP levels can be used as surrogate markers for CKD risk, especially for females.

The rebirth of interest in renal tubular function

The measurement of glomerular filtration rate by the clearance of inulin or creatinine has evolved over the past 50 years into an estimated value based solely on plasma creatinine concentration. We have examined some of the misconceptions and misunderstandings of the classification of renal disease and its course, which have followed this evolution. Furthermore, renal plasma flow and tubular function, which in the past were estimated by the clearance of the exogenous aryl amine, para-aminohippurate, are no longer measured. Over the past decade, studies in experimental animals with reduced nephron mass and in patients with reduced renal function have identified small gut-derived, protein-bound uremic retention solutes ("uremic toxins") that are poorly filtered but are secreted into the lumen by organic anion transporters (OATs) in the proximal renal tubule. These are not effectively removed by conventional hemodialysis or peritoneal dialysis. Residual renal function, urine produced in patients with advanced renal failure or undergoing dialysis treatment, may represent, at least in part, secretion of fluid and uremic toxins, such as indoxyl sulfate, mediated by proximal tubule OATs and might serve as a useful survival function. In light of this new evidence of the physiological role of proximal tubule OATs, we suggest that measurement of renal tubular function and renal plasma flow may be of considerable value in understanding and managing chronic kidney disease. Data obtained in normal subjects indicate that renal plasma flow and renal tubular function might be measured by the clearance of the endogenous aryl amine, hippurate.

Long-term evolution of renal function in patients with type 2 diabetes mellitus: a registry-based retrospective cohort study

OBJECTIVES

To picture the 10-year evolution of renal function in patients with type 2 diabetes mellitus (T2DM) and chronic kidney disease (CKD) and to describe the risk factors for severe decline.

SETTING

Primary registration network with 97 general practitioners working in 55 practices sending routinely collected patient data.

PARTICIPANTS

From the database, we selected all patients aged 40 years or older with T2DM and at least two creatinine measurements in two different years with an interval of at least 3 months. Based on the last available value of estimated glomerular filtration rate calculated by the modification of diet in renal disease (MDRD) equation, patients were divided into grades of CKD. Severe decline (decline of >4 mL/min/year) and 'certain drop' (CD, year-to-year decline >10 mL/min) were determined in patients with CKD. Determinants of severe decline and CD were investigated with logistic regression and longitudinal logistic regression analysis, respectively.

PRIMARY OUTCOME MEASURE

Kidney function (MDRD).

RESULTS

4041 patients, 1980 women, were included. The mean age was 71 years, mean diabetes duration was 7.7 years; 1514 (38%) suffered from CKD, 231 (15%) presented with severe decline and 18% of the patients with CKD presented with two or more CDs. Younger age, male gender, mean glycated haemoglobin and a higher number of CDs were significantly associated with the presence of severe decline (p<0.05); statins and higher diastolic blood pressure were significantly associated with the absence of severe decline (p<0.001). ACE inhibitors, other antihypertensive drugs and antidiabetic drugs including insulin therapy were specific determinants of CD.

CONCLUSIONS

CKD is highly prevalent in patients with T2DM; a minority of patients evolve into severe decline that is associated with younger age, male gender, 'CD' and manageable factors such as blood pressure, blood glucose, associated drugs prescriptions and statin therapy. Further prospective observational and experimental research is needed to clarify the nature of those associations.

Associations of kidney disease measures with mortality and end-stage renal disease in individuals with and without hypertension: a meta-analysis

BACKGROUND

Hypertension is the most prevalent comorbidity in individuals with chronic kidney disease. However, whether the association of the kidney disease measures, estimated glomerular filtration rate (eGFR) and albuminuria, with mortality or end-stage renal disease (ESRD) differs by hypertensive status is unknown.

METHODS

We did a meta-analysis of studies selected according to Chronic Kidney Disease Prognosis Consortium criteria. Data transfer and analyses were done between March, 2011, and June, 2012. We used Cox proportional hazards models to estimate the hazard ratios (HR) of mortality and ESRD associated with eGFR and albuminuria in individuals with and without hypertension.

FINDINGS

We analysed data for 45 cohorts (25 general population, seven high-risk, and 13 chronic kidney disease) with 1,127,656 participants, 364,344 of whom had hypertension. Low eGFR and high albuminuria were associated with mortality irrespective of hypertensive status in the general population and high-risk cohorts. All-cause mortality risk was 1·1-1·2 times higher in individuals with hypertension than in those without hypertension at preserved eGFR. A steeper relative risk gradient in individuals without hypertension than in those with hypertension at eGFR range 45-75 mL/min per 1·73 m(2) led to much the same mortality risk at lower eGFR. With a reference eGFR of 95 mL/min per 1·73 m(2) in each group to explicitly assess interaction, adjusted HR for all-cause mortality at eGFR 45 mL/min per 1·73 m(2) was 1·77 (95% CI 1·57-1·99) in individuals without hypertension versus 1·24 (1·11-1·39) in those with hypertension (p for overall interaction=0·0003). Similarly, for albumin-creatinine ratio of 300 mg/g (vs 5 mg/g), HR was 2·30 (1·98-2·68) in individuals without hypertension versus 2·08 (1·84-2·35) in those with hypertension (p for overall interaction=0·019). We recorded much the same results for cardiovascular mortality. The associations of eGFR and albuminuria with ESRD, however, did not differ by hypertensive status. Results for chronic kidney disease cohorts were similar to those for general and high-risk population cohorts.

INTERPRETATION

Chronic kidney disease should be regarded as at least an equally relevant risk factor for mortality and ESRD in individuals without hypertension as it is in those with hypertension.

FUNDING

US National Kidney Foundation.

Continuing exposure to low-dose nonylphenol aggravates adenine-induced chronic renal dysfunction and role of rosuvastatin therapy

Background

Nonylphenol (NP), an environmental organic compound, has been demonstrated to enhance reactive-oxygen species (ROS) synthesis. Chronic exposure to low-dose adenine (AD) has been reported to induce chronic kidney disease (CKD).

Methods

In this study, we tested the hypothesis that chronic exposure to NP will aggravate AD-induced CKD through increasing generations of inflammation, ROS, and apoptosis that could be attenuated by rosuvastatin. Fifty male Wistar rats were equally divided into group 1 (control), group 2 (AD in fodder at a concentration of 0.25%), group 3 (NP: 2 mg/kg/day), group 4 (combined AD & NP), and group 5 (AD-NP + rosuvastatin: 20 mg/kg/day). Treatment was continued for 24 weeks for all animals before being sacrificed.

Results

By the end of 24 weeks, serum blood urea nitrogen (BUN) and creatinine levels were increased in group 4 than in groups 1–3, but significantly reduced in group 5 as compared with group 4 (all p < 0.05). Histopathology scorings of renal-parenchymal and tubular damages were significantly higher in group 4 than in groups 1–3, but remarkably lower in group 5 compared with group 4 (all p < 0.01). Both gene and protein levels of inflammation, oxidative stress, ROS, and cellular apoptosis were remarkably higher in group 4 compared with groups 1–3, but lowered in group 5 than in group 4 (all p < 0.001). Conversely, both gene and protein levels of anti-oxidants, anti-inflammation and anti-apoptosis were markedly increased in group 5 compared with group 4 (all p < 0.001).

Conclusion

NP worsened AD-induced CKD that could be reversed by rosuvastatin therapy.

Predicting hospital cost in CKD patients through blood chemistry values

Background

Controversy exists in predicting costly hospitalization in patients with chronic kidney disease and co-morbid conditions. We therefore tested associations between serum chemistry values and the occurrence of in-patient hospital costs over a thirteen month study period. Secondarily, we derived a linear combination of variables to estimate probability of such occurrences in any patient.

Method

We calculated parsimonious values for select variables associated with in-patient hospitalization and compared sensitivity and specificity of these models to ordinal staging of renal disease.

Data from 1104 de-identified patients which included 18 blood chemistry observations along with complete claims data for all medical expenses.

We employed multivariable logistic regression for serum chemistry values significantly associated with in-patient hospital costs exceeding $3,000 in any single month and contrasted those results to other models by ROC area curves.

Results

The linear combination of weighted Z scores for parathyroid hormone, phosphorus, and albumin correlated with in-patient hospital care at p < 0.005. ROC curves derived from weighted variables of age, eGFR, hemoglobin, albumin, creatinine, and alanine aminotransferase demonstrated significance over models based on non-weighted Z scores for those same variables or CKD stage alone. In contrast, the linear combination of weighted PTH, PO4 and albumin demonstrated better prediction, but not significance over non-weighted Z scores for PTH alone.

Conclusion

Further study is justified to explore indices that predict costly hospitalization. Such metrics could assist Accountable Care Organizations in evaluating risk adjusted compensation for providers.

Rate of change in kidney function and the risk of death: the case for incorporating the rate of kidney function decline into the CKD staging system

Chronic kidney disease (CKD) is associated with increased risk of death. A wave of recent studies used longitudinal data to examine the effect of the rate of decline of kidney function on the risk of death. The results from these studies show that there is an independent and graded association between the rate of kidney function decline and the risk of death. There is a need to incorporate the rate of decline in the definition of CKD. This redefinition of CKD will transform a static definition into a dynamic one that more accurately describes the disease state in an individual patient.

Detection of chronic kidney disease with creatinine, cystatin C, and urine albumin-to-creatinine ratio and association with progression to end-stage renal disease and mortality

CONTEXT

A triple-marker approach for chronic kidney disease (CKD) evaluation has not been well studied.

OBJECTIVE

To evaluate whether combining creatinine, cystatin C, and urine albumin-to-creatinine ratio (ACR) would improve identification of risks associated with CKD compared with creatinine alone.

DESIGN, SETTING, AND PARTICIPANTS

Prospective cohort study involving 26,643 US adults enrolled in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study from January 2003 to June 2010. Participants were categorized into 8 groups defined by estimated glomerular filtration rate (GFR) determined by creatinine and by cystatin C of either <60 or ≥60 mL/min/1.73 m(2) and ACR of either <30 or ≥30 mg/g.

MAIN OUTCOME MEASURES

All-cause mortality and incident end-stage renal disease with median follow-up of 4.6 years.

RESULTS

Participants had a mean age of 65 years, 40% were black, and 54% were women. Of 26,643 participants, 1940 died and 177 developed end-stage renal disease. Among participants without CKD defined by creatinine, 24% did not have CKD by either ACR or cystatin C. Compared with those with CKD defined by creatinine alone, the hazard ratio for death in multivariable-adjusted models was 3.3 (95% confidence interval [CI], 2.0-5.6) for participants with CKD defined by creatinine and ACR; 3.2 (95% CI, 2.2-4.7) for those with CKD defined by creatinine and cystatin C, and 5.6 (95% CI, 3.9-8.2) for those with CKD defined by all biomarkers. Among participants without CKD defined by creatinine, 3863 (16%) had CKD detected by ACR or cystatin C. Compared with participants who did not have CKD by any measure, the HRs for mortality were 1.7 (95% CI, 1.4-1.9) for participants with CKD defined by ACR alone, 2.2 (95% CI, 1.9-2.7) for participants with CKD defined by cystatin C alone, and 3.0 (95% CI, 2.4-3.7) for participants with CKD defined by both measures. Risk of incident end-stage renal disease was higher among those with CKD defined by all markers (34.1 per 1000 person-years; 95% CI, 28.7-40.5 vs 0.33 per 1000 person-years; 95% CI, 0.05-2.3) for those with CKD defined by creatinine alone. The second highest end-stage renal disease rate was among persons missed by the creatinine measure but detected by both ACR and cystatin C (rate per 1000 person-years, 6.4; 95% CI, 3.6-11.3). Net reclassification improvement for death was 13.3% (P < .001) and for end-stage renal disease was 6.4% (P < .001) after adding estimated GFR cystatin C in fully adjusted models with estimated GFR creatinine and ACR.

CONCLUSION

Adding cystatin C to the combination of creatinine and ACR measures improved the predictive accuracy for all-cause mortality and end-stage renal disease.

The characteristics of new semi-quantitative method for diagnosing proteinuria by using random urine samples

We assessed the characteristics of the new semi-quantitative test paper (Clinitek ATLAS Pro(12)) using random urine samples. Three hundred urine samples were analyzed using either the new test paper, conventional dipsticks, quantitative (P/C ratio), or immunological quantitative methods (A/C ratio). Our study showed that the new test paper is highly sensitive and specific for the detection of urinary protein. The new test paper also detected the urine protein more accurately than the conventional test and has a lower false-positive rate. In addition, the new test paper detected 14 of the 300 patients (4.7%) as dilute urine samples needing reassessment. Seventeen of the 300 samples tested were negative with conventional dipsticks but positive with the new test paper. The new semi-quantitative test paper not only has higher sensitivity than the conventional dipstick method, but also has potential to detect dilute samples.

Rate of kidney function decline associates with mortality

The effect of rate of decline of kidney function on risk for death is not well understood. Using the Department of Veterans Affairs national databases, we retrospectively studied a cohort of 4171 patients who had rheumatoid arthritis and early stage 3 chronic kidney disease (CKD; estimated GFR 45 to 60 ml/min) and followed them longitudinally to characterize predictors of disease progression and the effect of rate of kidney function decline on mortality. After a median of 2.6 years, 1604 (38%) maintained stable kidney function; 426 (10%), 1147 (28%), and 994 (24%) experienced mild, moderate, and severe progression of CKD, respectively (defined as estimated GFR decline of 0 to 1, 1 to 4, and >4 ml/min per yr). Peripheral artery disease predicted moderate progression of CKD progression. Black race, hypertension, diabetes, cardiovascular disease, and peripheral artery disease predicted severe progression of CKD. After a median of 5.7 years, patients with severe progression had a significantly increased risk for mortality (hazard ratio 1.54; 95% confidence interval 1.30 to 1.82) compared with those with mild progression; patients with moderate progression exhibited a similar trend (hazard ratio 1.10; 95% confidence interval 0.98 to 1.30). Our results demonstrate an independent and graded association between the rate of kidney function decline and mortality. Incorporating the rate of decline into the definition of CKD may transform a static definition into a dynamic one that more accurately describes the potential consequences of the disease for an individual.

The association between age and nephrosclerosis on renal biopsy among healthy adults

BACKGROUND

Chronic kidney disease is common with older age and is characterized on renal biopsy by global glomerulosclerosis, tubular atrophy, interstitial fibrosis, and arteriosclerosis.

OBJECTIVE

To see whether the prevalence of these histologic abnormalities in the kidney increases with age in healthy adults and whether histologic findings are explained by age-related differences in kidney function or chronic kidney disease risk factors.

DESIGN

Cross-sectional study.

SETTING

Mayo Clinic, Rochester, Minnesota, from 1999 to 2009.

PATIENTS

1203 adult living kidney donors.

MEASUREMENTS

Core-needle biopsy of the renal cortex obtained during surgical implantation of the kidney, and medical record data of kidney function and risk factors obtained before donation.

RESULTS

The prevalence of nephrosclerosis (> or =2 chronic histologic abnormalities) was 2.7% (95% CI, 1.1% to 6.7%) for patients aged 18 to 29 years, 16% (CI, 12% to 20%) for patients aged 30 to 39 years, 28% (CI, 24% to 32%) for patients aged 40 to 49 years, 44% (CI, 38% to 50%) for patients aged 50 to 59 years, 58% (CI, 47% to 67%) for patients aged 60 to 69 years, and 73% (CI, 43% to 90%) for patients aged 70 to 77 years. Adjustment for kidney function and risk factor covariates did not explain the age-related increase in the prevalence of nephrosclerosis.

LIMITATION

Kidney donors are selected for health and lack the spectrum or severity of renal pathologic findings in the general population.

CONCLUSION

Kidney function and chronic kidney disease risk factors do not explain the strong association between age and nephrosclerosis in healthy adults.

PRIMARY FUNDING SOURCE

National Institutes of Health, U.S. Public Health Service.

The association between age and nephrosclerosis on renal biopsy among healthy adults

BACKGROUND

Chronic kidney disease is common with older age and is characterized on renal biopsy by global glomerulosclerosis, tubular atrophy, interstitial fibrosis, and arteriosclerosis.

OBJECTIVE

To see whether the prevalence of these histologic abnormalities in the kidney increases with age in healthy adults and whether histologic findings are explained by age-related differences in kidney function or chronic kidney disease risk factors.

DESIGN

Cross-sectional study.

SETTING

Mayo Clinic, Rochester, Minnesota, from 1999 to 2009.

PATIENTS

1203 adult living kidney donors.

MEASUREMENTS

Core-needle biopsy of the renal cortex obtained during surgical implantation of the kidney, and medical record data of kidney function and risk factors obtained before donation.

RESULTS

The prevalence of nephrosclerosis (> or =2 chronic histologic abnormalities) was 2.7% (95% CI, 1.1% to 6.7%) for patients aged 18 to 29 years, 16% (CI, 12% to 20%) for patients aged 30 to 39 years, 28% (CI, 24% to 32%) for patients aged 40 to 49 years, 44% (CI, 38% to 50%) for patients aged 50 to 59 years, 58% (CI, 47% to 67%) for patients aged 60 to 69 years, and 73% (CI, 43% to 90%) for patients aged 70 to 77 years. Adjustment for kidney function and risk factor covariates did not explain the age-related increase in the prevalence of nephrosclerosis.

LIMITATION

Kidney donors are selected for health and lack the spectrum or severity of renal pathologic findings in the general population.

CONCLUSION

Kidney function and chronic kidney disease risk factors do not explain the strong association between age and nephrosclerosis in healthy adults.

PRIMARY FUNDING SOURCE

National Institutes of Health, U.S. Public Health Service.

Metabolic syndrome and chronic kidney disease

The prevalence of metabolic syndrome (MetS) is increasing worldwide in both developing and developed countries. Experimental and clinical studies have revealed that MetS plays an important role in the development of chronic kidney disease (CKD), which leads to end-stage renal disease. Emerging evidence also suggests that CKD may actually cause MetS since the kidney is an important organ of glucose and lipid homeostasis. Although multiple mechanisms have been shown to be involved in the pathogenesis of MetS, insulin resistance appears to be a central pathophysiological factor contributing to MetS. In this review we will discuss the association of MetS with insulin resistance and CKD, and the renal pathophysiological changes associated with MetS.

High prevalence of undiagnosed chronic kidney disease among at-risk population in Kinshasa, the Democratic Republic of Congo

Background

There is limited knowledge of Chronic Kidney Disease (CKD) among high risk populations, especially in the developing countries. We report our study of testing for CKD in at-risk subjects.

Methods

In a cross-sectional study, 527 people from primary and secondary health care areas in the city of Kinshasa were studied from a random sample of at-risk out-patients with hypertension, diabetes, obesity, or HIV+. We measured blood pressure (BP), blood glucose level, proteinuria, body mass index, and estimated glomerular filtration rate (eGFR by MDRD equation) using calibrated creatinine levels based on one random measurement. The associations between health characteristics, indicators of kidney damage (proteinuria) and kidney function (<60 ml/min/1.73 m²) were also examined.

Results

The prevalence of CKD in this study was 36%, but only 12% were aware of their condition. 4% of patients had stage 1 CKD, 6% stage 2, 18% stage 3, 2% stage 4, and 6% had stage 5. 24 hour quantitative proteinuria (>300 mg/day) was found in 19%. In those with the at-risk conditions, the % of CKD was: 44% in patients with hypertension, 39% in those with diabetes; 16% in the obese and 12% in those who were HIV+. 82% of those with a history of diabetes had elevated serum glucose levels at screening (≥ 126 mg/dl). Only 6% of individuals with hypertension having CKD had reduced BP to lower than 130/80 mmHg. In multivariate analysis, diabetes, proteinuria and hypertension were the strongest determinants of CKD 3+.

Conclusion

It appears that one out of three people in this at-risk population has undiagnosed CKD and poorly controlled CKD risk factors. This growing problem poses clear challenges to this developing country. Therefore, CKD should be addressed through the development of multidisciplinary teams and improved communication between traditional health care givers and nephrology services. Attention to CKD risk factors must become a priority.

Demographic and clinical characteristics associated with glomerular filtration rates in living kidney donors

Due to the shortage of organs, living donor acceptance criteria are becoming less stringent. An accurate determination of the glomerular filtration rate (GFR) is critical in the evaluation of living kidney donors and a value exceeding 80 ml/min per 1.73 m(2) is usually considered suitable. To improve strategies for kidney donor screening, an understanding of factors that affect GFR is needed. Here we studied the relationships between donor GFR measured by (125)I-iothalamate clearances (mGFR) and age, gender, race, and decade of care in living kidney donors evaluated at the Cleveland Clinic from 1972 to 2005. We report the normal reference ranges for 1057 prospective donors (56% female, 11% African American). Females had slightly higher mGFR than males after adjustment for body surface area, but there were no differences due to race. The lower limit of normal for donors (5th percentile) was less than 80 ml/min per 1.73 m(2) for females over age 45 and for males over age 40. We found a significant doubling in the rate of GFR decline in donors over age 45 as compared to younger donors. The age of the donors and body mass index increased over time, but their mGFR, adjusted for body surface area, significantly declined by 1.49+/-0.61 ml/min per 1.73 m(2) per decade of testing. Our study shows that age and gender are important factors determining normal GFR in living kidney donors.

Combining GFR and albuminuria to classify CKD improves prediction of ESRD

Despite the high prevalence of chronic kidney disease (CKD), relatively few individuals with CKD progress to ESRD. A better understanding of the risk factors for progression could improve the classification system of CKD and strategies for screening. We analyzed data from 65,589 adults who participated in the Nord-Trøndelag Health (HUNT 2) Study (1995 to 1997) and found 124 patients who progressed to ESRD after 10.3 yr of follow-up. In multivariable survival analysis, estimated GFR (eGFR) and albuminuria were independently and strongly associated with progression to ESRD: Hazard ratios for eGFR 45 to 59, 30 to 44, and 15 to 29 ml/min per 1.73 m(2) were 6.7, 18.8, and 65.7, respectively (P < 0.001 for all), and for micro- and macroalbuminuria were 13.0 and 47.2 (P < 0.001 for both). Hypertension, diabetes, male gender, smoking, depression, obesity, cardiovascular disease, dyslipidemia, physical activity and education did not add predictive information. Time-dependent receiver operating characteristic analyses showed that considering both the urinary albumin/creatinine ratio and eGFR substantially improved diagnostic accuracy. Referral based on current stages 3 to 4 CKD (eGFR 15 to 59 ml/min per 1.73 m(2)) would include 4.7% of the general population and identify 69.4% of all individuals progressing to ESRD. Referral based on our classification system would include 1.4% of the general population without losing predictive power (i.e., it would detect 65.6% of all individuals progressing to ESRD). In conclusion, all levels of reduced eGFR should be complemented by quantification of urinary albumin to predict optimally progression to ESRD.

Kidney stones and the risk for chronic kidney disease

BACKGROUND AND OBJECTIVES

Kidney stones lead to chronic kidney disease (CKD) in people with rare hereditary disorders (e.g., primary hyperoxaluria, cystinuria), but it is unknown whether kidney stones are an important risk factor for CKD in the general population.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Among Olmsted County, MN, residents, all stone formers (n = 4774) whose condition was diagnosed in 1986 through 2003 were matched 1:3 to control subjects (n = 12,975). Cox proportional hazards models adjusted for age, gender, and comorbidities (hypertension, diabetes, obesity, dyslipidemia, gout, alcohol abuse, tobacco use, coronary artery disease, heart failure, cerebral infarct, and peripheral vascular disease) were used to assess the risk for incident CKD defined as a clinical diagnosis (diagnostic codes), ESRD or death with CKD, sustained (>90 d) elevated serum creatinine (>1.3 mg/dl in men, >1.1 mg/dl in women), or sustained estimated GFR <60 ml/min per 1.73 m(2).

RESULTS

During a mean of 8.6 yr of follow-up, stone formers were at increased risk for a clinical diagnosis of CKD, but an increased risk for ESRD or death with CKD was NS. Among patients with follow-up serum creatinine levels, stone formers were at increased risk for a sustained elevated serum creatinine and a sustained reduced GFR.

CONCLUSIONS

Kidney stones are a risk factor for CKD, and studies are warranted to assess screening and preventive measures for CKD in stone formers.

Predictivity of survival according to different equations for estimating renal function in community-dwelling elderly subjects

BACKGROUND

Detection of subjects with early chronic kidney disease (CKD) is important because some will progress up to stage 5 CKD, and most are at high risk of cardiovascular morbidity and mortality. While validity and precision of estimated glomerular filtration rate (eGFR) equations in tracking true GFR have been repeatedly investigated, their prognostic performance for mortality has not been hitherto compared. This is especially relevant in an elderly population in whom the risk of death is far more common than progression.

METHODS

We analysed data of participants in the InCHIANTI study, a community-based cohort study of older adults. Twenty-four-hour creatinine clearance (Ccr), Cockcroft-Gault (C-G) and Modification of Diet in Renal Disease (MDRD)-derived equations (six and four input variables) were calculated at enrolment (1998-2000), and all-cause mortality and cardiovascular mortality were prospectively ascertained by Cox regression over a 6-year follow-up.

RESULTS

Of the 1270 participants, 942 (mean age 75 years) had complete data for this study. The mean renal function ranged from 77 ml/min/1.73 m(2) by Ccr to 64 ml/min/1.73 m(2) by C-G. Comparisons among equations using K/DOQI staging highlight relevant mismatches, with a prevalence of CKD ranging from 22% (MDRD-4) to 40% (C-G). Reduced renal function was a strong independent predictor of death. In a Cox model--adjusted for demographics, physical activity, comorbidities, proteinuria and inflammatory parameters-participants with Ccr 60-90 ml/min/1.73 m(2) and Ccr <60 ml/min/1.73 m(2) were, respectively, 1.70 (95% CI: 1.02-2.83) and 1.91 (95% CI: 1.11-3.29) times more likely to die over the follow-up compared to those with Ccr >90 ml/min/1.73 m(2). For the C-G, the group with values <60 ml/min/1.73 m(2) had a significant higher all-cause mortality compared to those with values >90 ml/min/1.73 m(2) (HR 2.59, 95% CI: 1.13-5.91). The classification based on the MDRD formulae did not provide any significant prognostic information. The adjusted risk of all-cause mortality followed a similar pattern when Ccr and estimating equations were introduced as continuous variables or dichotomized as higher or lower than 60 ml/min. C-G was the best prognostic indicator of cardiovascular mortality. Possibly, Ccr and C-G are better prognostic indicators than MDRD-derived equations because they incorporate a stronger effect of age.

CONCLUSIONS

In a South-European elderly population, the prevalence of CKD is high and varies widely according to the method adopted to estimate GFR. Researchers and clinicians who want to capture the prognostic information on mortality related to kidney function should use the Ccr or C-G formula and not MDRD equations. These results highlight the importance of strategies for early detection and clinical management of CKD in elderly subjects.

Rapid kidney function decline and mortality risk in older adults

BACKGROUND

Impaired kidney function is associated with increased mortality risk in older adults. It remains unknown, however, whether longitudinal declines in kidney function are independently associated with increased cardiovascular and all-cause mortality in older adults.

METHODS

The Cardiovascular Health Study evaluated a cohort of community-dwelling older adults enrolled from 1989 to 1993 in 4 US communities with follow-up through 2005. Among 4380 participants, the slope of annual decline in estimated glomerular filtration rate (eGFR) was estimated using both serum creatinine (eGFR(creat)) and cystatin C (eGFR(cys)) rates, which were measured at baseline, year 3, and year 7 of follow-up. Rapid decline in eGFR was defined as a loss greater than 3 mL/min/1.73 m(2) per year, and cardiovascular and all-cause mortality were assessed over a mean of 9.9 years of follow-up.

RESULTS

Mean (SD) levels of creatinine and cystatin C were 0.93 (0.30) mg/dL and 1.03 (0.25) mg/L, respectively; mean (SD) eGFR(creat) and eGFR(cys) were 79 (23) mL/min/1.73 m(2) and 79 (19) mL/min/1.73 m(2), respectively. Individuals with rapid decline measured by eGFR(creat) (n = 714; 16%) had increased risk of cardiovascular (adjusted hazard ratio [AHR], 1.70; 95% confidence interval [CI], 1.40-2.06) and all-cause (AHR, 1.73; 95% CI, 1.54-1.94) mortality. Individuals with rapid decline measured by eGFR(cys) (n = 1083; 25%) also had increased risk of cardiovascular (AHR, 1.53; 95% CI, 1.29-1.80) and all-cause (AHR, 1.53; 95% CI, 1.38-1.69) mortality. The association of rapid decline in eGFR with elevated mortality risk did not differ across subgroups based on baseline kidney function, age, sex, race, or prevalent coronary heart disease.

CONCLUSION

Rapid decline in eGFR is associated with an increased risk of cardiovascular and all-cause mortality in older adults, independent of baseline eGFR and other demographic variables.

All-cause mortality attributable to chronic kidney disease: a prospective cohort study based on 462 293 adults in Taiwan

BACKGROUND

Both end-stage renal disease and chronic kidney disease are increasing worldwide; however, the full effect of chronic kidney disease is unknown because mortality risks for all five stages are unavailable. We assessed prevalence and mortality risks for all stages of chronic kidney disease and quantified its attributable mortality in Taiwan.

METHODS

The cohort consisted of 462 293 individuals aged older than 20 years who participated in a standard medical screening programme since 1994. As of Dec 31, 2006, we identified 14 436 deaths. Chronic kidney disease was determined by glomerular filtration rate and urinary protein. We estimated national prevalence in Taiwan from the cohort by adjusting age and educational levels. Hazard ratios (HRs) were calculated with Cox proportionate hazards model. We calculated mortality attributable to chronic kidney disease for national population and for low socioeconomic status.

FINDINGS

The national prevalence of chronic kidney disease was 11.93% (95% CI 11.66-12.28), but only 3.54% (3.37-3.68) of participants in the cohort were aware of their disorder. Prevalence was substantially higher in the group with low socioeconomic status than in the high status group (19.87% [19.84-19.91] vs 7.33% [7.31-7.35]). 56 977 (12%) of cohort participants had chronic kidney disease; those with disease had 83% higher mortality for all cause (HR 1.83 [1.73-1.93]) and 100% higher for cardiovascular diseases (2.00 [1.78-2.25]), in a cohort that was observed for 13 years with median follow-up of 7.5 years (IQR 4.0-10.1). 10.3% (95% CI 9.57-11.03) of deaths in the entire population were attributable to chronic kidney disease, but 17.5% (16.27-18.67) of deaths in the low socioeconomic status population. 2350 (39%) deaths occurred before 65 years of age in those with chronic kidney disease. Regular users of Chinese herbal medicines had a 20% (odds ratio 1.20 [1.16-1.24]) increased risk of developing chronic kidney disease.

INTERPRETATION

The high prevalence of chronic kidney disease and its associated all-cause mortality, especially in people with low socioeconomic status, make reduction of this disorder a public-health priority. Promotion of its recognition through the general public knowing their glomerular filtration rate and testing their urine is crucial to reduce premature deaths from all causes and to attenuate this global epidemic.