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1.  Risk Factors for Chronic Kidney Disease among American Indians and Alaska Natives – Findings from the Kidney Early Evaluation Program 
American Journal of Nephrology  2008;29(5):440-446.
Background
American Indians and Alaska Natives (AIAN) have a high incidence of end-stage renal disease. Less is known about chronic kidney disease (CKD) among AIAN and whether risk factors differ for low estimated glomerular filtration rate (eGFR) versus albuminuria with a normal eGFR.
Methods
Cross-sectional study examining the associations of age, sex, smoking, obesity, diabetes, hypertension, family history, and geographic region with CKD among a screened population of AIAN participants in the Kidney Early Evaluation Program from 2000 to 2006. CKD was defined by the presence of either a low eGFR, <60 ml/min/1.73 m2, or albuminuria, a urine albumin/creatinine ratio ≥30 mg/g.
Results
The prevalence of any CKD was 29%, of low eGFR was 17%, and of albuminuria with a normal eGFR was 12%. Older age was the strongest predictor of low eGFR (61+ years OR 8.42, 95% CI 5.92–11.98), followed by hypertension (OR 2.38, 95% CI 1.74–3.26). In contrast, diabetes (OR 2.04, 95% CI 1.57–2.64) and hypertension (OR 2.63, 95% CI 1.93–3.59) were the only predictors of albuminuria among persons with a normal eGFR.
Conclusion
The burden of CKD was high among this screened population of AIAN, and different risk factor patterns were associated with low eGFR and albuminuria. Innovative programs and longitudinal research are needed to address CKD among AIAN.
doi:10.1159/000174857
PMCID: PMC2821946  PMID: 19011277
Chronic kidney disease; Risk factors; American Indians; Alaska Natives
2.  25-hydroxyvitamin D Levels and chronic kidney disease in the AusDiab (Australian Diabetes, Obesity and Lifestyle) study 
BMC Nephrology  2012;13:55.
Background
Low 25-hydroxy vitamin D (25(OH)D) levels have been associated with an increased risk of albuminuria, however an association with glomerular filtration rate (GFR) is not clear. We explored the relationship between 25(OH)D levels and prevalent chronic kidney disease (CKD), albuminuria and impaired GFR, in a national, population-based cohort of Australian adults (AusDiab Study).
Methods
10,732 adults ≥25 years of age participating in the baseline survey of the AusDiab study (1999–2000) were included. The GFR was estimated using an enzymatic creatinine assay and the CKD-EPI equation, with CKD defined as eGFR <60 ml/min/1.73 m2. Albuminuria was defined as a spot urine albumin to creatinine ratio (ACR) of ≥2.5 mg/mmol for men and ≥3.5 for women. Serum 25(OH)D levels of <50 nmol/L were considered vitamin D deficient. The associations between 25(OH)D level, albuminuria and impaired eGFR were estimated using multivariate regression models.
Results
30.7% of the study population had a 25(OH)D level <50 nmol/L (95% CI 25.6-35.8). 25(OH)D deficiency was significantly associated with an impaired eGFR in the univariate model (OR 1.52, 95% CI 1.07-2.17), but not in the multivariate model (OR 0.95, 95% CI 0.67-1.35). 25(OH)D deficiency was significantly associated with albuminuria in the univariate (OR 2.05, 95% CI 1.58-2.67) and multivariate models (OR 1.54, 95% CI 1.14-2.07).
Conclusions
Vitamin D deficiency is common in this population, and 25(OH)D levels of <50 nmol/L were independently associated with albuminuria, but not with impaired eGFR. These associations warrant further exploration in prospective and interventional studies.
doi:10.1186/1471-2369-13-55
PMCID: PMC3441805  PMID: 22759247
Albuminuria; Chronic kidney disease; Glomerular filtration rate; and Vitamin D
3.  Prevalence estimates of chronic kidney disease in Canada: results of a nationally representative survey 
Background:
Chronic kidney disease is an important risk factor for death and cardiovascular-related morbidity, but estimates to date of its prevalence in Canada have generally been extrapolated from the prevalence of end-stage renal disease. We used direct measures of kidney function collected from a nationally representative survey population to estimate the prevalence of chronic kidney disease among Canadian adults.
Methods:
We examined data for 3689 adult participants of cycle 1 of the Canadian Health Measures Survey (2007–2009) for the presence of chronic kidney disease. We also calculated the age-standardized prevalence of cardiovascular risk factors by chronic kidney disease group. We cross-tabulated the estimated glomerular filtration rate (eGFR) with albuminuria status.
Results:
The prevalence of chronic kidney disease during the period 2007–2009 was 12.5%, representing about 3 million Canadian adults. The estimated prevalence of stage 3–5 disease was 3.1% (0.73 million adults) and albuminuria 10.3% (2.4 million adults). The prevalence of diabetes, hypertension and hypertriglyceridemia were all significantly higher among adults with chronic kidney disease than among those without it. The prevalence of albuminuria was high, even among those whose eGFR was 90 mL/min per 1.73 m2 or greater (10.1%) and those without diabetes or hypertension (9.3%). Awareness of kidney dysfunction among adults with stage 3–5 chronic kidney disease was low (12.0%).
Interpretation:
The prevalence of kidney dysfunction was substantial in the survey population, including individuals without hypertension or diabetes, conditions most likely to prompt screening for kidney dysfunction. These findings highlight the potential for missed opportunities for early intervention and secondary prevention of chronic kidney disease.
doi:10.1503/cmaj.120833
PMCID: PMC3680588  PMID: 23649413
4.  Blood pressure and chronic kidney disease progression in a multi-racial cohort: the Multi-Ethnic Study of Atherosclerosis 
Journal of human hypertension  2013;27(7):10.1038/jhh.2013.1.
The relationship between blood pressure (BP) and kidney function among individuals with chronic kidney disease (CKD) remains controversial. This study evaluated the association between BP and estimated glomerular filtration rate (eGFR) decline among adults with nondiabetic stage 3 CKD. The Multi-Ethnic Study of Atherosclerosis participants with an eGFR 30–59 ml min–1 per 1.73 m2 at baseline without diabetes were included. Participants were followed over a 5-year period. Kidney function change was determined by annualizing the change in eGFR using cystatin C, creatinine and a combined equation. Risk factors for progression of CKD (defined as a decrease in annualized eGFR >2.5 ml min–1 per 1.73 m2) were identified using univariate analyses and sequential logistic regression models. There were 220 participants with stage 3 CKD at baseline using cystatin C, 483 participants using creatinine and 381 participants using the combined equation. The median (interquartile range) age of the sample was 74 (68–79) years. The incidence of progression of CKD was 16.8% using cystatin C and 8.9% using creatinine (P = 0.002). Systolic BP >140 mm Hg or diastolic BP >90 mm Hg was significantly associated with progression using a cystatin C-based (odds ratio (OR), 2.49; 95% confidence interval (CI), 1.12–5.52) or the combined equation (OR, 2.07; 95% CI, 1.16–3.69), but not when using creatinine after adjustment for covariates. In conclusion, with the inclusion of cystatin C in the eGFR assessment hypertension was an important predictor of CKD progression in a multi-ethnic cohort with stage 3 CKD.
doi:10.1038/jhh.2013.1
PMCID: PMC3830562  PMID: 23407373
blood pressure; glomerular filtration rate; renal disease; cystatin C; creatinine; ethnicity
5.  The impact of different GFR estimating equations on the prevalence of CKD and risk groups in a Southeast Asian cohort using the new KDIGO guidelines 
BMC Nephrology  2012;13:1.
Background
Recently, the Kidney Disease: Improving Global Outcomes (KDIGO) group recommended that patients with CKD should be assigned to stages and composite relative risk groups according to GFR (G) and proteinuria (A) criteria. Asians have among the highest rates of ESRD in the world, but establishing the prevalence and prognosis CKD is a problem for Asian populations since there is no consensus on the best GFR estimating (eGFR) equation. We studied the effects of the choice of new Asian and Caucasian eGFR equations on CKD prevalence, stage distribution, and risk categorization using the new KDIGO classification.
Methods
The prevalence of CKD and composite relative risk groups defined by eGFR from with Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI); standard (S) or Chinese(C) MDRD; Japanese CKD-EPI (J-EPI), Thai GFR (T-GFR) equations were compared in a Thai cohort (n = 5526)
Results
There was a 7 fold difference in CKD3-5 prevalence between J-EPI and the other Asian eGFR formulae. CKD3-5 prevalence with S-MDRD and CKD-EPI were 2 - 3 folds higher than T-GFR or C-MDRD. The concordance with CKD-EPI to diagnose CKD3-5 was over 90% for T-GFR or C-MDRD, but they only assigned the same CKD stage in 50% of the time. The choice of equation also caused large variations in each composite risk groups especially those with mildly increased risks. Different equations can lead to a reversal of male: female ratios. The variability of different equations is most apparent in older subjects. Stage G3aA1 increased with age and accounted for a large proportion of the differences in CKD3-5 between CKD-EPI, S-MDRD and C-MDRD.
Conclusions
CKD prevalence, sex ratios, and KDIGO composite risk groupings varied widely depending on the equation used. More studies are needed to define the best equation for Asian populations.
doi:10.1186/1471-2369-13-1
PMCID: PMC3274433  PMID: 22226403
EGAT; glomerular filtration rate; renal failure; epidemiology, classification; kidney; Thai
6.  Uric Acid, Hypertension, and CKD among Alaska Eskimos—the Genetics of Coronary Artery Disease in Alaska Natives (GOCADAN) Study 
It is unknown what role uric acid may play in the increasing cardiovascular disease (CVD) among Alaska Eskimos. Uric acid is associated with both hypertension (HTN) and chronic kidney disease (CKD). We analyzed 1078 Genetics of Coronary Artery Disease in Alaska Natives (GOCADAN) participants. Estimated glomerular filtration rate (eGFR) was calculated from serum creatinine measures using the MDRD equation. CKD was defined by an eGFR of <60ml/min/1.73m2. We adjusted for age, sex, education, diabetes, hypertension (or eGFR), obesity, lipids, and smoking status; 7% (n=75) had prevalent CKD. eGFR decreased with increasing tertiles of serum uric acid. (p<0.001) Uric acid was independently associated with prevalent CKD (Adjusted Odds Ratio [OR] and 95% confidence interval [CI] of 2.04 (1.62–2.56), respectively). 21% (n=230) had prevalent HTN; Uric acid was independently associated with prevalent HTN (Adjusted OR 1.2, 95% CI 1.1–1.5). Uric acid is independently associated with prevalent CKD and HTN in this population.
doi:10.1111/j.1751-7176.2011.00574.x
PMCID: PMC3507473  PMID: 22277138
Alaska Eskimos; chronic kidney disease; epidemiology; hypertension; uric acid
7.  The Association between Parathyroid Hormone Levels and Hemoglobin in Diabetic and Nondiabetic Participants in the National Kidney Foundation's Kidney Early Evaluation Program 
Cardiorenal Medicine  2013;3(2):120-127.
Background
Both anemia and secondary hyperparathyroidism are reflections of hormonal failure in chronic kidney disease (CKD). While the association of elevated levels of parathyroid hormone (PTH) and anemia has been studied among those with advanced CKD, less is known about this association in mild-to-moderate CKD.
Methods
In a cross-sectional analysis, the relationship between PTH and hemoglobin levels was investigated in 10,750 participants in the National Kidney Foundation's Kidney Early Evaluation Program with an estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m2.
Results
In the unadjusted analysis, higher PTH levels were associated with lower hemoglobin levels. However, after multivariable adjustment for age, race, gender, smoking status, education, cardiovascular disease, diabetes, hypertension, cancer, albuminuria, BMI, baseline eGFR, calcium, and phosphorus, the direction of association changed. As compared to the first PTH quintile, hemoglobin levels were 0.09 g/dl (95% CI: 0.01-0.18), 0.15 g/dl (95% CI: 0.07-0.24), 0.18 g/dl (95% CI: 0.09-0.26), and 0.13 g/dl (95% CI: 0.07-0.25) higher for the second, third, fourth, and fifth quintiles, respectively. Similarly, each standard deviation increase in natural log transformed PTH was associated with a 0.06 g/dl (95% CI: 0.03-0.09, p = 0.0003) increase in hemoglobin. However, a significant effect modification was seen for diabetes (p = 0.0003). Each standard deviation increase in natural log transformed PTH was associated with a 0.10 g/dl (95% CI: 0.054-0.138, p < 0.0001) increase in hemoglobin, while no association was seen among those without diabetes mellitus.
Conclusion
After multivariable adjustment, there was a small positive association between PTH and hemoglobin among diabetics but not among nondiabetics.
doi:10.1159/000351229
PMCID: PMC3721130  PMID: 23922552
Chronic kidney disease; Anemia; Secondary hyperparathyroidism

8.  Association of Chronic Kidney Disease with Atrial Fibrillation Among Adults in the United States: Reasons for Geographic and Racial Differences in Stroke (REGARDS) Study 
Background
Atrial fibrillation (AF) is common among patients with end-stage renal disease, but few data are available on its prevalence among adults with chronic kidney disease (CKD) of lesser severity.
Methods and Results
We evaluated the association of CKD with electrocardiogram-detected AF among 26,917 participants in the REasons for Geographic and Racial Differences in Stroke (REGARDS) study, a population-based cohort of African-American and white US adults ≥45 years of age. Estimated glomerular filtration rate (eGFR) was calculated using the abbreviated Modification of Diet in Renal Disease study equation and albuminuria was defined as a urinary albumin to creatinine ratio ≥30 mg/g. Participants were categorized by renal function: no CKD (eGFR ≥60 ml/min/1.73m2 without albuminuria, n=21,081), stage 1–2 CKD (eGFR ≥60 ml/min/1.73m2 with albuminuria n=2,938), stage 3 CKD (eGFR 30 to 59 ml/min/1.73m2, n=2,683) and stage 4–5 CKD (eGFR <30 ml/min/1.73m2, n=215). The prevalence of AF among participants without CKD, and with stage 1–2, stage 3, and stage 4–5 CKD was 1.0%, 2.8%, 2.7% and 4.2%, respectively. Compared to participants without CKD, the age, race, sex adjusted odds ratios for prevalent AF were 2.67 (95% CI 2.04 – 3.48), 1.68 (95% CI 1.26 – 2.24) and 3.52 (95% CI 1.73–7.15) among those with stage 1–2, stage 3 and stage 4–5 CKD. The association between CKD and prevalent AF remained statistically significant after further multivariable adjustment and was consistent across numerous subgroups.
Conclusions
- Regardless of severity, CKD is associated with an increased prevalence of AF among US adults.
doi:10.1161/CIRCEP.110.957100
PMCID: PMC3049935  PMID: 21076159
chronic kidney disease; atrial fibrillation; electrocardiography
9.  Relationship between Stage of Kidney Disease and Incident Heart Failure in Older Adults 
American Journal of Nephrology  2011;34(2):135-141.
Background
The relationship between stage of chronic kidney disease (CKD) and incident heart failure (HF) remains unclear.
Methods
Of the 5,795 community-dwelling adults ≥65 years in the Cardiovascular Health Study, 5,450 were free of prevalent HF and had baseline estimated glomerular filtration rate (eGFR: ml/min/1.73 m2) data. Of these, 898 (16%) had CKD 3A (eGFR 45–59 ml/min/1.73 m2) and 242 (4%) had CKD stage ≥3B (eGFR <45 ml/min/1.73 m2). Data on baseline proteinuria were not available and 4,310 (79%) individuals with eGFR ≥60 ml/min/1.73 m2 were considered to have no CKD. Propensity scores estimated separately for CKD 3A and ≥3B were used to assemble two cohorts of 1,714 (857 pairs with CKD 3A and no CKD) and 557 participants (148 CKD ≥3B and 409 no CKD), respectively, balanced on 50 baseline characteristics.
Results
During 13 years of follow-up, centrally-adjudicated incident HF occurred in 19, 24 and 38% of pre-match participants without CKD (reference), with CKD 3A [unadjusted hazard ratio (HR) 1.40; 95% confidence interval (CI) 1.20–1.63; p < 0.001] and with CKD ≥3B (HR 3.37; 95% CI 2.71–4.18; p < 0.001), respectively. In contrast, among matched participants, incident HF occurred in 23 and 23% of those with CKD 3A and no CKD, respectively (HR 1.03; 95% CI 0.85–1.26; p = 0.746), and 36 and 28% of those with CKD ≥3B and no CKD, respectively (HR 1.44; 95% CI 1.04–2.00; p = 0.027).
Conclusions
Among community-dwelling older adults, CKD is a marker of incident HF regardless of stage; however, CKD ≥3B, not CKD 3A, has a modest independent association with incident HF.
doi:10.1159/000328905
PMCID: PMC3136373  PMID: 21734366
Chronic kidney disease; Heart failure
10.  High Prevalence of Stage 3 Chronic Kidney Disease in Older Adults Despite Normal Serum Creatinine 
BACKGROUND
Serum creatinine is commonly used to diagnose chronic kidney disease (CKD), but may underestimate CKD in older adults when compared with using glomerular filtration rates (eGFR). The magnitude of this underestimation is not clearly defined.
OBJECTIVE
Using the Modification of Diet in Renal Disease (MDRD) equation, to describe both the prevalence and the magnitude of underestimation of stage 3 CKD (GFR 30–59 ml/min/1.73 m2), as well as ideal serum creatinine cutoff values to diagnose stage 3 CKD among Americans ≥65 years of age.
DESIGN
Cross-sectional.
PARTICIPANTS
A total of 3,406 participants ≥65 years of age from the 1999–2004 National Health and Nutrition Examination Surveys (NHANES).
MEASUREMENTS
Serum creatinine levels were used to determine eGFR from the MDRD equation. Information on clinical conditions was self-reported.
RESULTS
Overall, 36.1% of older adults in the US have stage 3 or greater CKD as defined by eGFR values. Among older adults with stage 3 CKD, 80.6% had creatinine values ≤1.5 mg/dl, and 38.6% had creatinine values ≤1.2 mg/dl. Optimal cutoff values for serum creatinine in the diagnosis of stage 3 CKD in older adults were ≥1.3 mg/dl for men and ≥1.0 mg/dl for women, regardless of the presence or absence of hypertension, diabetes, or congestive heart failure.
CONCLUSION
Use of serum creatinine underestimates the presence of advanced (stage 3 or greater) CKD among older adults in the US. Automated eGFR reporting may improve the accuracy of risk stratification for older adults with CKD.
doi:10.1007/s11606-008-0850-3
PMCID: PMC2607515  PMID: 18987917
chronic kidney disease; serum creatinine; older adults; glomerular filtration rate
11.  Association of estimated glomerular filtration rate and albuminuria with mortality and end-stage renal disease: a collaborative meta-analysis of kidney disease cohorts 
Kidney international  2011;79(12):1331-1340.
Limited data are available on the independent associations of estimated glomerular filtration rate (eGFR) and albuminuria with mortality and end stage renal disease (ESRD) among individuals with chronic kidney disease (CKD). We conducted a collaborative meta-analysis of 21,688 participants selected for CKD from 13 cohorts.
After adjustment for potential confounders and albuminuria, a 15 mL/min/1.73 m2 lower eGFR below 45 mL/min/1.73 m2 was significantly associated with mortality (pooled hazard ratio [HR] 1.47 [95% CI: 1.22–1.79]), and ESRD (pooled HR 6.24 [95% CI: 4.84–8.05]). There was significant heterogeneity between studies for both HR estimates. After adjustment for risk factors and eGFR, an eight-fold higher albumin:creatinine ratio (ACR) or protein:creatinine ratio (PCR) was significantly associated with mortality (pooled HR 1.40 [95% CI: 1.27–1.55]), without evidence of significant heterogeneity. An eight-fold higher ACR or PCR was also strongly associated with ESRD (pooled HR 3.04 [95% CI: 2.27–4.08]), with significant heterogeneity between HR estimates.
Lower eGFR and more severe albuminuria independently predict mortality and ESRD among individuals selected for CKD. The associations are stronger for ESRD than for mortality. The observed associations are consistent with CKD classification based on eGFR stages, and suggest that albuminuria provides additional prognostic information among individuals with CKD.
doi:10.1038/ki.2010.550
PMCID: PMC3917543  PMID: 21289598
12.  Association between First Nations ethnicity and progression to kidney failure by presence and severity of albuminuria 
Background:
Despite a low prevalence of chronic kidney disease (estimated glomerular filtration rate [GFR] < 60 mL/min per 1.73 m2), First Nations people have high rates of kidney failure requiring chronic dialysis or kidney transplantation. We sought to examine whether the presence and severity of albuminuria contributes to the progression of chronic kidney disease to kidney failure among First Nations people.
Methods:
We identified all adult residents of Alberta (age ≥ 18 yr) for whom an outpatient serum creatinine measurement was available from May 1, 2002, to Mar. 31, 2008. We determined albuminuria using urine dipsticks and categorized results as normal (i.e., no albuminuria), mild, heavy or unmeasured. Our primary outcome was progression to kidney failure (defined as the need for chronic dialysis or kidney transplantation, or a sustained doubling of serum creatinine levels). We calculated rates of progression to kidney failure by First Nations status, by estimated GFR and by albuminuria category. We determined the relative hazard of progression to kidney failure for First Nations compared with non–First Nations participants by level of albuminuria and estimated GFR.
Results:
Of the 1 816 824 participants we identified, 48 669 (2.7%) were First Nations. First Nations people were less likely to have normal albuminuria compared with non–First Nations people (38.7% v. 56.4%). Rates of progression to kidney failure were consistently 2- to 3-fold higher among First Nations people than among non–First Nations people, across all levels of albuminuria and estimated GFRs. Compared with non–First Nations people, First Nations people with an estimated GFR of 15.0–29.9 mL/min per 1.73 m2 had the highest risk of progression to kidney failure, with similar hazard ratios for those with normal and heavy albuminuria.
Interpretation:
Albuminuria confers a similar risk of progression to kidney failure for First Nations and non–First Nations people.
doi:10.1503/cmaj.130776
PMCID: PMC3903763  PMID: 24295865
13.  High rates of albuminuria but not of low eGFR in Urban Indigenous Australians: the DRUID Study 
BMC Public Health  2011;11:346.
Background
Indigenous Australians have an incidence of end stage kidney disease 8-10 times higher than non-Indigenous Australians. The majority of research studies concerning Indigenous Australians have been performed in rural or remote regions, whilst the majority of Indigenous Australians actually live in urban settings. We studied prevalence and factors associated with markers of kidney disease in an urban Indigenous Australian cohort, and compared results with those for the general Australian population.
Methods
860 Indigenous adult participants of the Darwin Region Urban Indigenous Diabetes (DRUID) Study were assessed for albuminuria (urine albumin-creatinine ratio≥2.5 mg/mmol males, ≥3.5 mg/mmol females) and low eGFR (estimated glomular filtration rate < 60 mls/min/1.73 m2). Associations between risk factors and kidney disease markers were explored. Comparison was made with the AusDiab cohort (n = 8,936 aged 25-64 years), representative of the general Australian adult population.
Results
A high prevalence of albuminuria (14.8%) was found in DRUID, whilst prevalence of low eGFR was 2.4%. Older age, higher HbA1c, hypertension, higher C-reactive protein and current smoking were independently associated with albuminuria on multiple regression. Low eGFR was independently associated with older age, hypertension, albuminuria and higher triglycerides. Compared to AusDiab participants, DRUID participants had a 3-fold higher adjusted risk of albuminuria but not of low eGFR.
Conclusions
Given the significant excess of ESKD observed in Indigenous versus non-Indigenous Australians, these findings could suggest either: albuminuria may be a better prognostic marker of kidney disease than low eGFR; that eGFR equations may be inaccurate in the Indigenous population; a less marked differential between Indigenous and non-Indigenous Australians for ESKD rates in urban compared to remote regions; or that differences in the pathophysiology of chronic kidney disease exist between Indigenous and non-Indigenous populations.
doi:10.1186/1471-2458-11-346
PMCID: PMC3112138  PMID: 21595912
14.  Association of CKD with Disability in the United States 
Background
Little is known about disability in early-stage chronic kidney disease (CKD).
Study Design
Cross-sectional national survey (National Health and Nutrition Examination Survey 1999–2006).
Setting and Participants
Community-based survey of 16,011 non-institutionalized U.S. civilian adults (≥20 years).
Predictor
CKD, categorized as: no CKD, stages 1 and 2 [albuminuria and estimated glomerular filtration rate (eGFR) ≥60 ml/min/1.73 m2], and stages 3 and 4 (eGFR 15–59).
Outcome
Self-reported disability, defined by limitations in working, walking, and cognition; and difficulties in activities of daily living (ADL), instrumental ADL, leisure and social activities, lower extremity mobility, and general physical activity.
Measurements
Albuminuria and eGFR assessed from urine and blood samples; disability, demographics, access to care, and comorbid conditions assessed by standardized questionnaire.
Results
Age-adjusted prevalence of reported limitations was generally significantly greater with CKD: e.g., difficulty with ADLs was reported by 17.6%, 24.7%, and 23.9% of older (≥65 years) and 6.8%, 11.9%, and 11.0% of younger (20–64 years) adults with no CKD, stages 1 and 2, and stages 3 and 4, respectively. CKD was also associated with greater reported limitations and difficulty in other activities after age adjustment, including instrumental ADL, leisure and social activities, lower extremity mobility, and general physical activity. Other demographics, socioeconomic status, and access to care generally only slightly attenuated the observed associations, particularly among older individuals; adjustment for cardiovascular disease, arthritis, and cancer attenuated most associations such that statistical significance was no longer achieved.
Limitations
Inability to establish causality and possible unmeasured confounding.
Conclusion
CKD is associated with higher prevalence of disability in the United States. Age and other comorbid conditions account for most, but not all, of this association.
doi:10.1053/j.ajkd.2010.08.016
PMCID: PMC3025052  PMID: 21036441
chronic kidney disease; disability; activities of daily living; limitations; employment; physical functioning; cognitive functioning
15.  Comparative effectiveness of incident oral antidiabetic drugs on kidney function 
Kidney International  2012;81(7):698-706.
Diabetes is a major cause of chronic kidney disease, and oral antidiabetic drugs are the mainstay of therapy for most patients with Type 2 diabetes. Here we evaluated their role on renal outcomes by using a national Veterans Administration database to assemble a retrospective cohort of 93,577 diabetic patients who filled an incident oral antidiabetic drug prescription for metformin, sulfonylurea, or rosiglitazone, and had an estimated glomerular filtration rate (eGFR) of 60 ml/min or better. The primary composite outcome was a persistent decline in eGFR from baseline of 25% or more (eGFR event) or a diagnosis of end-stage renal disease (ESRD). The secondary outcome was an eGFR event, ESRD, or death. Sensitivity analyses included using a more stringent definition of the eGFR event requiring an eGFR <60 ml/min per 1.73 m2 in addition to the 25% or more decline; controlling for baseline proteinuria thereby restricting data to 15,065 patients; and not requiring persistent treatment with the initial oral antidiabetic drug. Compared to patients using metformin, sulfonylurea users had an increased risk for both the primary and the secondary outcome, each with an adjusted hazard ratio of 1.20. Results of sensitivity analyses were consistent with the main findings. The risk associated with rosiglitazone was similar to metformin for both outcomes. Thus, compared to metformin, oral antidiabetic drug treatment with sulfonylureas increased the risk of a decline in eGFR, ESRD, or death.
doi:10.1038/ki.2011.444
PMCID: PMC3306005  PMID: 22258320
chronic kidney disease; diabetes; diabetic nephropathy
16.  Lower estimated GFR and higher albuminuria are associated with adverse kidney outcomes in both general and high-risk populations 
Kidney international  2011;80(1):93-104.
Both low eGFR and albuminuria are known risk factors for ESRD. This paper focuses on their joint contribution to ESRD and other kidney outcomes.
We performed a collaborative meta-analysis of 9 general population cohorts with 845,125 participants and 8 cohorts with 173,892 participants selected because of high risk for chronic kidney disease. Both eGFR and albuminuria were tested as risk factors for ESRD, acute kidney injury and progressive chronic kidney disease.
In general population cohorts, the risk for ESRD was unrelated to eGFR at values 75–105 ml/min/1.73m2 and increased exponentially at lower eGFR. Hazard ratios (95% confidence interval) at eGFR 60, 45, and 15 (versus 95) ml/min/1.73m2 were 3.69 (2.36–5.76), 29.3 (19.5–44.1) and 454.9 (112.4–1840.2), respectively, after adjustment for albumin-to-creatinine ratio and cardiovascular risk factors. Albuminuria was associated with ESRD risk linearly without thresholds. Adjusted hazard ratios at albumin-to-creatinine ratios 30, 300 and 1000 (versus 5) mg/g were 4.87 (2.30–10.3), 13.4 (5.49–32.7) and 28.4 (14.9–54.2), respectively. eGFR and albuminuria were multiplicatively associated with ESRD, without evidence for interaction. Similar, but numerically less pronounced associations were observed for acute kidney injury and progressive chronic kidney disease. The findings in high risk cohorts were generally comparable to those in general population cohorts.
In conclusion, lower eGFR and higher albuminuria are risk factors for ESRD, acute kidney injury and progressive chronic kidney disease independent of each other and of cardiovascular risk factors, both in the general population and high risk cohorts.
doi:10.1038/ki.2010.531
PMCID: PMC3959732  PMID: 21289597
Meta-analysis; eGFR (kidney function); albumin-to-creatinine ratio (albuminuria); dipstick (proteinuria); ESRD (end-stage renal disease); acute kidney injury; progressive chronic kidney disease
17.  Metabolic Syndrome Predicts New Onset of Chronic Kidney Disease in 5,829 Patients With Type 2 Diabetes 
Diabetes Care  2008;31(12):2357-2361.
OBJECTIVE—Type 2 diabetes is the leading cause of end-stage renal disease worldwide. Aside from hyperglycemia and hypertension, other metabolic factors may determine renal outcome. We examined risk associations of metabolic syndrome with new onset of chronic kidney disease (CKD) in 5,829 Chinese patients with type 2 diabetes enrolled between 1995 and 2005.
RESEARCH DESIGN AND METHODS—Metabolic syndrome was defined by National Cholesterol Education Program Adult Treatment Panel III criteria with the Asian definition of obesity. Estimated glomerular filtration rate (eGFR) was calculated using the abbreviated Modification of Diet in Renal Disease formula modified for the Chinese population. New onset of CKD was defined as eGFR <60 ml/min per 1.73 m2 at the time of censor. Subjects with CKD at baseline were excluded from the analysis.
RESULTS—After a median follow-up duration of 4.6 years (interquartile range: 1.9–7.3 years), 741 patients developed CKD. The multivariable-adjusted hazard ratio (HR) of CKD was 1.31 (95% CI 1.12–1.54, P = 0.001) for subjects with metabolic syndrome compared with those without metabolic syndrome. Relative to subjects with no other components of metabolic syndrome except for diabetes, those with two, three, four, and five metabolic syndrome components had HRs of an increased risk of CKD of 1.15 (0.83–1.60, P = 0.407) 1.32 (0.94–1.86, P = 0.112), 1.64 (1.17–2.32, P = 0.004), and 2.34 (1.54–3.54, P < 0.001), respectively. The metabolic syndrome traits of central obesity, hypertriglyceridemia, hypertension, and low BMI were independent predictors for CKD.
CONCLUSIONS—The presence of metabolic syndrome independently predicts the development of CKD in subjects with type 2 diabetes.
doi:10.2337/dc08-0971
PMCID: PMC2584195  PMID: 18835954
18.  The Association between Parathyroid Hormone Levels and the Cardiorenal Metabolic Syndrome in Non-Diabetic Chronic Kidney Disease 
Cardiorenal Medicine  2011;1(2):123-130.
Aims
The relationship between parathyroid hormone (PTH) and the cardiorenal metabolic syndrome was examined among non-diabetic persons with chronic kidney disease (CKD).
Methods
In a cross-sectional analysis, the relationship between PTH levels and the cardiorenal metabolic syndrome was investigated in 3,215 non-diabetic participants in the National Kidney Foundation-Kidney Early Evaluation Program (KEEP 2.0) found to have CKD (eGFR <60 ml/min/1.73 m2).
Results
In unadjusted analyses, the prevalence of the cardiorenal metabolic syndrome increased along increasing PTH quartiles (31.7, 33.8, 37.3, and 48.7%, respectively, p for trend <0.0001). After multivariate adjustment, as compared to the first PTH quartile, odds of the cardiorenal metabolic syndrome were 16% (p = 0.18), 35% (p = 0.006), and 80% (p < 0.0001) higher for the second, third, and fourth quartiles, respectively. When taken as a continuous predictor, each standard deviation increase of natural log transformed PTH was associated with 26% (p < 0.0001) higher odds of the cardiorenal metabolic syndrome. The association of PTH with the cardiorenal metabolic syndrome was not modified by age or gender (p for interaction was not significant for both modifiers).
Conclusions
Among an outpatient non-diabetic population with CKD, higher PTH levels were associated with a higher prevalence of the cardiorenal metabolic syndrome.
doi:10.1159/000327149
PMCID: PMC3101512  PMID: 22258399
Chronic kidney disease; Hyperparathyroidism; KEEP; Metabolic syndrome
19.  Carboxymethyl-lysine, an advanced glycation end product, and decline of renal function in older community-dwelling adults 
European journal of nutrition  2008;48(1):38-44.
Background
Advanced glycation end products (AGEs) are bioactive molecules found in greater concentrations in foods that have been processed at high temperatures. AGEs have been associated with impaired renal function in diabetes and in uremia. The relationship between AGEs and renal function in community-dwelling adults has not been well characterized.
Aim of the Study
The objective was to determine whether plasma AGEs are independently associated with chronic kidney disease (CKD) and predictive of renal function in older adults.
Methods
The relationship between plasma carboxymethyl-lysine (CML), an AGE, and CKD (≥stage 3 of National Kidney Foundation classification; estimated glomerular filtration rate [eGFR] <60 mL/min/1.73 m2) and eGFR at 3- and 6-years follow-up was examined in a population-based study of aging, the InCHIANTI study, in Tuscany, Italy.
Results
Of 1,008 adults, aged ≥65 years, 153 (15.2%) had CKD at enrollment. Mean (Standard Deviation [S.D.]) plasma CML was 365 (110) ng/mL. Plasma CML was associated with CKD (Odds Ratio [O.R.] expressed per 1 S.D., 1.53, 95% Confidence Interval [C.I.] 1.27-1.84, P <0.0001) in a multivariate logistic regression model, adjusting for potential confounders. Plasma CML was associated with eGFR (beta = -2.77, standard error [S.E.] = 0.51, P <0.0001) at baseline, 3-year (beta = -2.54, S.E. = 0.61, P <0.0001) and 6-year follow-up visits (beta = -1.21, S.E. = 0.70, P = 0.08) in multivariate linear regression models, adjusting for potential confounders. The associations between plasma CML and prevalent CKD, eGFR, and eGFR at 3- and 6-year follow-up were significant and nearly unchanged after exclusion of adults with diabetes.
Conclusion
Plasma CML is independently associated with CKD and is an independent predictor of decline in renal function in older community-dwelling adults.
doi:10.1007/s00394-008-0757-0
PMCID: PMC2637810  PMID: 19031098
advanced glycation end products; aging; carboxymethyl-lysine; chronic kidney disease; renal function
20.  Chronic Kidney Disease Identification in a High-Risk Urban Population: Does Automated eGFR Reporting Make a Difference? 
Whether automated estimated glomerular filtration rate (eGFR) reporting for patients is associated with improved provider recognition of chronic kidney disease (CKD), as measured by diagnostic coding of CKD in those with laboratory evidence of the disease, has not been explored in a poor, ethnically diverse, high-risk urban patient population. A retrospective cohort of 237 adult patients (≥20 years) with incident CKD (≥1 eGFR ≥60 ml/min/1.73 m2, followed by ≥2 eGFRs <60 ml/min/1.73 m2 ≥3 months apart)—pre- or postautomated eGFR reporting—was identified within the San Francisco Department of Public Health Community Health Network (January 2005–July 2009). Patients were considered coded if any ICD-9-CM diagnostic codes for CKD (585.x), other kidney disease (580.x–581.x, 586.x), or diabetes (250.4) or hypertension (403.x, 404.x) CKD were present in the medical record within 6 months of incident CKD. Multivariable logistic regression was used to obtain adjusted odds ratios (ORs) for CKD coding. We found that, pre-eGFR reporting, 42.5 % of incident CKD patients were coded for CKD. Female gender, increased age, and non-Black race were associated with lower serum creatinine and lower prevalence of coding but comparable eGFR. Prevalence of coding was not statistically significantly higher overall (49.6 %, P = 0.27) or in subgroups after the institution of automated eGFR reporting. However, gaps in coding by age and gender were narrowed post-eGFR, even after adjustment for sociodemographic and clinical characteristics: 47.9 % of those <65 and 30.3 % of those ≥65 were coded pre-eGFR, compared to 49.0 % and 52.0 % post-eGFR (OR = 0.43 and 1.16); similarly, 53.2 % of males and 25.4 % of females were coded pre-eGFR compared to 52.8 % and 44.0 % post-eGFR (OR 0.28 vs. 0.64). Blacks were more likely to be coded in the post-eGFR period: OR = 1.08 and 1.43 (Pinteraction > 0.05). Automated eGFR reporting may help improve CKD recognition, but it is not sufficient to resolve underidentification of CKD by safety net providers.
doi:10.1007/s11524-012-9726-2
PMCID: PMC3531349  PMID: 22684427
Chronic kidney disease; Diagnostic coding; Estimated glomerular filtration rate; Female; African American
21.  Cystatin C and Albuminuria as Risk Factors for Development of CKD Stage 3: The Multi-Ethnic Study of Atherosclerosis (MESA) 
Background
The growing burden and morbidity of chronic kidney disease (CKD) warrant effective strategies for identifying those at increased risk. We examined the association of cystatin C and albuminuria with development of CKD stage 3.
Study Design
Prospective observational study.
Setting and Participants
5,422 participants from the Multi-Ethnic Study of Atherosclerosis with estimated glomerular filtration rate (eGFR) ≥ 60 ml/min/1.73m2.
Predictor
Participants were categorized into four mutually exclusive groups: presence or absence of microalbuminuria (albumin-creatinine ratio >17 and > 25 µg/mg in men and women, respectively) in those with or without cystatin C ≥ 1.0 mg/L.
Outcomes and Measurements
Incident CKD stage 3 was defined as eGFR < 60 ml/min/1.73m2 at the 3rd or 4th visit and an annual decline of > 1 ml/min/1.73 m2. Poisson regression was used to evaluate incident rate ratios in unadjusted and adjusted analyses that include baseline eGFR.
Results
Mean age was 61 years, 49% were men, 38% white, 11% had diabetes, 13.7% had cystatin C ≥ 1mg/L, 8.4% had microalbuminuria, and 2.7 % had cystatin C ≥ 1 mg/L with microalbuminuria. 554 (10%) participants developed CKD stage 3 over a median follow-up of 4.7 years and the adjusted incidence rate ratios (95% CI) were 1.57 (1.19–2.07), 1.37 (1.13–1.66), and 2.12 (1.61–2.80) in those with microalbuminuria, cystatin C ≥ 1 mg/L, and both, respectively, compared to those with neither.
Limitations
Relatively short follow up and absence of measured GFR.
Conclusions
Cystatin C and microalbuminuria are independent risk factors for incident CKD stage 3 and could be useful as screening tools to identify those at increased risk.
doi:10.1053/j.ajkd.2010.11.021
PMCID: PMC3090544  PMID: 21296473
22.  Association between family members of dialysis patients and chronic kidney disease: a multicenter study in China 
BMC Nephrology  2013;14:19.
Background
Family members of patients with end stage renal disease were reported to have an increased prevalence of chronic kidney disease (CKD). However, studies differentiated genetic and non-genetic family members are limited. We sought to investigate the prevalence of CKD among fist-degree relatives and spouses of dialysis patients in China.
Methods
Seventeen dialysis facilities from 4 cities of China including 1062 first-degree relatives and 450 spouses of dialysis patients were enrolled. Sex- and age- matched controls were randomly selected from a representative sample of general population in Beijing. CKD was defined as decreased estimated glomerular (eGFR < 60 mL/min/1.73 m2) or albuminuria.
Results
The prevalence of eGFR less than 60 mL/min/1.73 m2, albuminuria and the overall prevalence of CKD in dialysis spouses were compared with their counterpart controls, which was 3.8% vs. 7.8% (P < 0.01), 16.8% vs. 14.6% (P = 0.29) and 18.4% vs. 19.8% (P = 0.61), respectively. The prevalence of eGFR less than 60 mL/min/1.73 m2, albuminuria and the overall prevalence of CKD in dialysis relatives were also compared with their counterpart controls, which was 1.5% vs. 2.4% (P = 0.12), 14.4% vs. 8.4% (P < 0.01) and 14.6% vs. 10.5% (P < 0.01), respectively. Multivariable Logistic regression analysis indicated that being spouses of dialysis patients is negatively associated with presence of low eGFR, and being relatives of dialysis patients is positively associated with presence of albuminuria.
Conclusions
The association between being family members of dialysis patients and presence of CKD is different between first-degree relatives and spouses. The underlying mechanisms deserve further investigation.
doi:10.1186/1471-2369-14-19
PMCID: PMC3565899  PMID: 23331610
Chronic kidney disease; Albuminuria; Renal function; Relatives; Spouses; Screening
23.  Kidney Function and Cognitive Impairment in US Adults: The REGARDS (Reasons for Geographic and Racial Differences in Stroke) Study 
Background
The association between kidney function and cognitive impairment has not been assessed in a national sample with a wide spectrum of kidney disease severity.
Study Design
Cross-sectional.
Setting & Participants
23,405 participants [EF1](mean age 64.9 ± 9.6 years) with baseline measurements of creatinine and cognitive function participating in the REGARDS (REasons for Geographic And Racial Differences in Stroke) Study, a study of stroke risk factors in a large national sample.
Predictor
Estimated glomerular filtration rate (eGFR).
Outcome
Cognitive impairment.
Measurements
Chronic kidney disease (CKD) was defined as an eGFR <60 ml/min/1.73m2 Kidney function was analyzed in 10 ml/min/1.73 m2 increments among those with CKD, and in exploratory analyses, across the range of kidney function. Cognitive function was assessed using the Six-item Screener and participants with a score ≤4 were considered to have cognitive impairment.
Results
CKD was associated with an increased prevalence of cognitive impairment, independent of confounding factors (odds ratio (OR) 1.23, 95% confidence interval (95% CI) 1.06, 1.43). Among those with CKD, each 10 ml/min/1.73m2 decrease in eGFR below 60 ml/min/1.73m2 was associated with an 11% increased prevalence of impairment (OR 1.11, 95% CI 1.04, 1.19). Exploratory analyses revealed a non-linear association between eGFR and the prevalence of cognitive impairment, with a significant, increased prevalence of impairment among those with eGFR <50 and ≥100 ml/min/1.73m2.
Limitations
Longitudinal measures of cognitive function were not available.
Conclusions
Among US adults, lower levels of kidney function are associated with an increased prevalence of cognitive impairment. The prevalence of impairment appears to increase early in the course of kidney disease; therefore screening for impairment should be considered among all adults with CKD.
doi:10.1053/j.ajkd.2008.05.004
PMCID: PMC2593146  PMID: 18585836
CKD; cognitive function; cognitive impairment
24.  Fibroblast growth factor-23 and early decrements in kidney function: the Heart and Soul Study 
Background. Fibroblast growth factor-23 (FGF-23) is associated with mortality in dialysis patients, and concentrations are elevated in moderate chronic kidney disease (CKD). The threshold of CKD or albuminuria at which FGF-23 begins to change is unknown.
Methods. In 792 outpatients with stable cardiovascular disease (CVD) and normal kidney function to moderate CKD, we evaluate the associations of estimated glomerular filtration rate (eGFR) and albumin-to-creatinine ratio (ACR) with plasma FGF-23 concentrations.
Results. Compared to participants with eGFR ≥90 ml/min/1.73m2, mean FGF-23 concentrations were 7.8 RU/ml higher (4.3–11.5, P = 0.01) in those with eGFR 60–89 ml/min/1.73m2 in models adjusted for age, sex, race, ACR, blood pressure, diabetes and body mass index. More advanced decrements in eGFR were associated with much higher FGF-23 concentrations. In spline analysis, the slope of change in FGF-23 concentration was evident at eGFR <90 ml/min/1.73m2. Compared to participants with ACR <30 mg/g, mean FGF-23 concentrations were 18.4 RU/ml higher (9.3–29.2, P < 0.001) in those with ACR 30–299 mg/g in models adjusted for identical covariates plus eGFR and much higher in individuals with ACR ≥300 mg/g. Spline analysis demonstrated a linear relationship of ACR with FGF-23, independent of eGFR, even among persons with ACR <30 mg/g.
Conclusion. Modest decrements in eGFR or elevations in albuminuria are each independently associated with higher FGF-23 concentrations in outpatients with stable CVD.
doi:10.1093/ndt/gfp699
PMCID: PMC2902926  PMID: 20037168
albuminuria; chronic; fibroblast growth factor-23; kidney disease; osteodystrophy
25.  Estimating Glomerular Filtration Rate in Diabetes Using Serum Cystatin C 
Chronic kidney disease (CKD) is a major public health problem, especially for people with diabetes. Not only is it a risk factor for end-stage renal disease (ESRD) but it is also a major cardiovascular disease (CVD) risk factor. Methods that accurately and simply estimate glomerular filtration rate (GFR) are therefore needed to optimise the detection and management of CKD in people with diabetes. One of the main failures of commonly used creatinine-based methods for estimating renal function is that they lack applicability across the full range of GFR values and underestimate GFR levels >60 mL/min/1.73m2. Methods for accurately estimating an early pathological decline in GFR (i.e. ΔGFR >3.3 mL/min/year before reaching a GFR <60 mL/min/1.73m2) are especially needed as appropriate interventions have been shown to retard progression to ESRD and reduce CVD risk in people with diabetes. In contrast, recent studies have suggested that estimates of GFR based on serum cystatin C concentration might provide a simple and accurate method for detecting and monitoring an early decline in renal function.
PMCID: PMC3100282  PMID: 21611078

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