Kidney function and discrimination of cardiovascular risk in middle-aged men

Prevalent Rate of Nonalbuminuric Renal Insufficiency and Its Association with Cardiovascular Disease Event in Korean Type 2 Diabetes

BACKGROUND

Nonalbuminuric renal insufficiency is a unique category of diabetic kidney diseases. The objectives of the study were to evaluate prevalent rate of nonalbuminuric renal insufficiency and to investigate its relationship with previous cardiovascular disease (CVD) event in Korean patients with type 2 diabetes mellitus (T2DM).

METHODS

Laboratory and clinical data of 1,067 subjects with T2DM were obtained and reviewed. Study subjects were allocated into four subgroups according to the CKD classification. Major CVD events were included with coronary, cerebrovascular, and peripheral vascular events.

RESULTS

Nonalbuminuric stage ≥3 CKD group, when compared with albuminuric stage ≥3 CKD group, had shorter diabetic duration, lower concentrations of glycated hemoglobin, high density lipoprotein cholesterol, and high-sensitivity C-reactive protein, lower prevalent rates of retinopathy and previous CVD, and higher rate of treatment with angiotensin-converting enzyme inhibitors/angiotensin II receptor blockers. Nonalbuminuric stage ≥3 CKD group showed a greater association with prior CVD events than no CKD group; however, albuminuric stage ≥3 CKD group made addition to increase prevalence of prior CVD events significantly when CKD categories were applied as covariates. Association of prior CVD events, when compared with normal estimated glomerular filtration rate (eGFR) and nonalbuminuria categories, became significant for declined eGFR, which was higher for eGFR of <30 mL/min/1.73 m², and albuminuria.

CONCLUSION

The results show that subjects with nonalbuminuric stage ≥3 CKD is significantly interrelated with occurrence of prior CVD events than those with normal eGFR with or without albuminuria. Comparing with normal eGFR and nonalbuminuria categories, the combination of increased degree of albuminuria and declined eGFR is becoming significant for the association of prior CVD events.

Low glomerular filtration rate and risk of myocardial infarction: A systematic review and meta-analysis

BACKGROUND

Chronic kidney disease is increasing in prevalence. The association between low baseline estimated glomerular filtration rate (eGFR) and future myocardial infarction has not been comprehensively assessed.

METHODS

A systematic review and meta-analysis of observational studies evaluating the risk for future myocardial infarction associated with eGFR <60 and 60-90ml/min/1.73m² was completed. Data sources included PubMed, EMBASE, and the Cochrane Library. Included studies were required to have prospectively collected data, followed subjects for at least 6months, and reported baseline eGFR levels and the multivariable-adjusted relative risk for future myocardial infarction. A random effects model was used and subgroup analyses were conducted.

RESULTS

26 publications representing 41 observational cohorts were selected. In total, 1,986,850 participants with more than 35,752 documented myocardial infarctions (follow-up range: 9months to ~20years) were evaluated. eGFR <60ml/min/1.73m² was associated with a relative risk of 1.52 (95% confidence interval 1.39-1.67; p<0.00001) while eGFR 60-90ml/min/1.73m² was associated with a relative risk of 1.21 (1.09-1.34; p=0.0002) for myocardial infarction. Significant heterogeneity existed among both eGFR groups. Subgroup analysis found a further increase in risk for myocardial infarction as eGFR declined from 30 to 60 to <30ml/min/1.73m² (1.40, 95% confidence interval, 1.21-1.61 vs.1.94, 95% confidence interval, 1.51-2.50; p=0.03).

CONCLUSIONS

Decreased baseline eGFR is independently associated with increased future myocardial infarction, and the risk increases with advanced renal insufficiency. Clinicians should be wary of acute coronary syndromes in patients with CKD.

The Envy of Scholars: Applying the Lessons of the Framingham Heart Study to the Prevention of Chronic Kidney Disease

During the past 50 years, a dramatic reduction in the mortality rate associated with cardiovascular disease has occurred in the US and other countries. Statistical modeling has revealed that approximately half of this reduction is the result of risk factor mitigation. The successful identification of such risk factors was pioneered and has continued with the Framingham Heart Study, which began in 1949 as a project of the US National Heart Institute (now part of the National Heart, Lung, and Blood Institute). Decreases in total cholesterol, blood pressure, smoking, and physical inactivity account for 24%, 20%, 12%, and 5% reductions in the mortality rate, respectively. Nephrology was designated as a recognized medical professional specialty a few years later. Hemodialysis was first performed in 1943. The US Medicare End-Stage Renal Disease (ESRD) Program was established in 1972. The number of patients in the program increased from 5,000 in the first year to more than 500,000 in recent years. Only recently have efforts for risk factor identification, early diagnosis, and prevention of chronic kidney disease (CKD) been undertaken. By applying the approach of the Framingham Heart Study to address CKD risk factors, we hope to mirror the success of cardiology; we aim to prevent progression to ESRD and to avoid the cardiovascular complications associated with CKD. In this paper, we present conceptual examples of risk factor modification for CKD, in the setting of this historical framework.

Albuminuria and renal function as predictors of cardiovascular events and mortality in a general population of patients with type 2 diabetes: a nationwide observational study from the Swedish National Diabetes Register

OBJECTIVE

Reduced renal function and albuminuria predict cardiovascular (CV) events and mortality in type 2 diabetes (T2D). In addition, we evaluated the role of co-existing congestive heart failure (CHF) and other CV risk factors on CV events in a large observational population-based cohort of T2D patients.

RESEARCH DESIGN AND METHODS

We included 66,065 patients with T2D who were reported to the National Diabetes Register (NDR) in Sweden between 2003-2006 with a follow-up of 5.7 years. Data on outcomes were collected from the cause of death and hospital discharge registers.

RESULTS

A total of 10% of patients experienced a CV event and 3.7% of these were fatal. Increasing levels of albuminuria and renal impairment were independently associated with increasing risk of CV events and all-cause mortality also when adjusting for CHF. In normoalbuminuric patients, a reduction in renal function is an important predictor of CV events and all-cause mortality. Glycaemic control (high HbA1c), smoking and hyperlipidaemia had important effects on risk for CV events in patients with albuminuria, while high blood pressure, but not glycaemic control, had an effect in patients with normoalbuminuric renal impairment.

CONCLUSION

Albuminuria and renal impairment are independent risk factors for CV outcomes and mortality in T2D, albuminuria being the strongest risk factor and relevant at all levels of renal function. In normoalbuminuric patients, a reduction in renal function is an important predictor of CV events and all-cause mortality.

A cardiovascular risk calculator for renal transplant recipients

BACKGROUND

Renal transplant recipients (RTRs) have increased cardiovascular disease (CVD) risk. Standard CVD risk calculators are poorly predictive in RTRs; we therefore aimed to develop and validate an equation for CVD risk prediction in this population.

METHODS

We used data from the Assessment of Lescol in Renal Transplantation trial, which are randomly divided into an assessment sample and a test sample (67% and 33%, respectively, of the total population). For variable selection in the assessment sample, backward stepwise Cox regression was used. Using the regression coefficients and centralized prognostic index, risk was calculated for individual patients. The equation was then validated for calibration and discrimination using the test sample.

RESULTS

Major adverse cardiac events could be predicted using a seven-variable model including age, previous coronary heart disease, diabetes, low-density lipoprotein, creatinine, number of transplants, and smoking. The calibration of the model was good in the test sample with a Hosmer-Lemeshow chi-square value of 11.47 and a P value of 0.245. The areas under the receiver operating characteristic curve were 0.738 in the assessment sample and 0.740 in the test sample. Total mortality could be predicted using a six-variable model including age, coronary heart disease, diabetes, creatinine, total time on renal replacement therapy, and smoking. The calibration of the model was acceptable in the test sample with a Hosmer-Lemeshow chi-square value of 13.08 and a P value of 0.109. The areas under the receiver operating characteristic curve were 0.734 in the assessment sample and 0.720 in the test sample.

CONCLUSIONS

Using the Assessment of Lescol in Renal Transplantation trial population, a formula for 7-year CVD and mortality risk calculation for prevalent RTRs has been developed.

Association between glomerular filtration rate and endothelial function in an elderly community cohort

BACKGROUND

Endothelial dysfunction is prevalent among individuals with chronic kidney disease. However, the association between glomerular filtration rate and endothelial function in the community is unclear and needs to be investigated in the general population.

METHODS

In the community-based Prospective Investigation of the Vasculature of Uppsala Seniors study (PIVUS, n = 952, mean age 70, women 49.3%), we investigated cross-sectional associations between estimated cystatin C-based glomerular filtration rate (eGFR), and 3 measures representing different aspects of endothelial function (endothelial-dependent vasodilation [EDV], endothelial independent vasodilatation [EIDV], and flow-mediated dilatation [FMD]). We also performed pre-specified sub-group analyses in participants with normal eGFR (>60 ml/min/1.73 m(2)).

RESULTS

In the whole cohort, 10 ml/min/1.73 m(2) higher eGFR was associated with 3% higher EDV (p = 0.001) and 2% higher EIDV (p = 0.007), adjusted for age and sex. The associations were attenuated and no longer statistically significant after adjusting for established cardiovascular risk factors. In participants with eGFR >60 ml/min/1.73 m(2), 10 ml higher eGFR was associated with 2% higher EDV (p = 0.04) after adjusting for sex and age. eGFR was not associated to FMD in any model or sub-sample.

CONCLUSION

This community-based study suggests that eGFR is associated with endothelial function also in persons with normal kidney function, but that this association is largely explained by confounding by established cardiovascular risk factors. Thus, our data do not support the notion of a direct causal interplay between renal and vascular function prior to the development of CKD.

A novel model of cardiovascular risk based on kidney function

BACKGROUND/AIMS

Although creatinine-based estimated glomerular filtration rate (eGFR) is associated with cardiovascular events, threshold values for optimum discrimination are unclear. We aimed to identify serum creatinine and eGFR thresholds of maximum sensitivity and specificity (Max(Sn+Sp)) for a composite outcome of coronary heart disease, stroke, and death.

METHODS

Classification tree methodology defined the hierarchical rank of serum creatinine, eGFR, and cardiovascular risk factors in adults aged 45-64 years (Atherosclerosis Risk in Communities Study, n = 15,582; follow-up, 13.1 years). The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), Modification of Diet in Renal Disease (MDRD) Study, and Cockcroft-Gault corrected for body surface area (CG/BSA) eGFR equations were used.

RESULTS

The mean study population age was 54.2 years; 26.4% were African-American. The mean standardized creatinine level was 0.83 mg/dl. The mean eGFR(CKD-EPI), eGFR(MDRD), and eGFR(CG/BSA) values were 95.7, 98.6, and 99.7 ml/min/1.73 m(2), respectively. The composite outcome occurred for 22.1% of the population. For all eGFR measures, sensitivity was <0.05 and specificity >0.98 for thresholds of 60 ml/min/1.73 m(2). Max(Sn+Sp) for serum creatinine occurred at 0.73 mg/dl (sensitivity 0.66/specificity 0.48); corresponding values for eGFR(CKD-EPI), eGFR(CG/BSA), and eGFR(MDRD) were 95 (0.52/0.59), 90 (0.44/0.67), and 75 (0.16/0.91) ml/min/1.73 m(2), respectively. Considering optimum thresholds for 10 modifiable risk factors, high-density lipoprotein cholesterol ≤44 mg/dl ranked first; rankings for optimum renal function thresholds varied between sixth and tenth.

CONCLUSIONS

Optimum eGFR thresholds for community-based risk triage were substantially higher than 60 ml/min/1.73 m(2), which currently defines moderate abnormality. Utility of creatinine-based risk triage in older adults appears modest.

Kidney function for the non-nephrologist: an emerging tool for predicting mortality risk

Estimated glomerular filtration rate (eGFR) and albuminuria are among the most important cardiovascular risk factors, but the optimal cutoff for predicting mortality may not yet have been agreed upon. Foley et al. analyzed data from the population-based NHANES III study with classification tree methodology. They found that an eGFR of 94 ml/min per 1.73 m(2) and an albumin-creatinine ratio of 9 mg/g were the optimal cutoff values, that is, more 'normal' values than are used to define chronic kidney disease.

Chronic kidney disease: a public health priority and harbinger of premature cardiovascular disease

The epidemics of cardiovascular disease, obesity, diabetes, HIV and cancer have all received much attention from the public, media and policymakers. By contrast, chronic kidney disease (CKD) has remained largely a 'silent' epidemic. This is unfortunate because early diagnosis of renal disease based on proteinuria and/or reduced estimated glomerular filtration rate could enable early intervention to reduce the high risks of cardiovascular events, end-stage renal disease (ESRD) and death that are associated with CKD. Given the global increase in the incidence of the leading causes of CKD--hypertension, obesity and diabetes mellitus--better disease management and prevention planning are needed, as effective strategies are available to slow the progression of CKD and reduce cardiovascular risk. CKD may be regarded as a clinical model of accelerated vascular disease and premature ageing, and the risk-factor profile changes during the progression from mild/moderate CKD to ESRD. Although many randomized controlled trials in patients with mild to moderate CKD have shown beneficial effects of interventions aimed at preventing the progression of CKD, most trials have been unable to demonstrate a beneficial effect of interventions aimed at improving outcome in ESRD. Thus, novel treatment strategies are needed in this high-risk patient group.

Cystatin C, mortality risk and clinical triage in US adults: threshold values and hierarchical importance

BACKGROUND

It has been suggested that cystatin C may be a superior measure of estimated glomerular filtration rate (eGFR) than creatinine-based methods. We aimed to assess the utility of cystatin C for clinical triage in community-based settings.

METHODS

We identified cystatin C thresholds that maximize sensitivity and specificity (Max(Sn + Sp)) for predicting death and subsequently applied classification tree methodology considering serum creatinine, creatinine-based eGFR, urinary albumin-creatinine ratio and conventional modifiable risk factors to define subgroups, interactions and hierarchical ranks in fasting US adults (National Health and Nutrition Examination Survey 1988-94, followed through 2006).

RESULTS

A threshold cystatin C value of 0.94 mg/L exhibited the best maximum combined value of sensitivity and specificity for predicting death (Max(Sn + Sp), Sn 0.64/Sp 0.78). When all variables were considered jointly in a classification tree, cystatin C and albumin-creatinine ratio were the primary mortality discriminators in subgroups that added up to 41 and 14% of the study population, respectively; serum creatinine and creatinine-based eGFR were non-discriminatory.

CONCLUSION

Cystatin C may be useful for risk-based clinical triage in public health settings.

Kidney function and risk triage in adults: threshold values and hierarchical importance

In this study, we attempted to identify threshold values for kidney function measures that maximally discriminate short-term mortality, to identify major population segments in which these thresholds apply, and to classify the hierarchical rank of the thresholds when other classic risk factors are also considered. To do this we retrospectively identified estimated glomerular filtration rate (eGFR) and urinary albumin-creatinine ratio (ACR) thresholds to maximize sensitivity and specificity predictions for death in non-institutionalized NHANES III participants, representative of the United States population from 1988 to 1994 and followed through 2000. In a classification tree excluding dichotomizing variables, age 57 years was initially selected; ACR appeared in the second round and eGFR in the third. The prognostic discrimination of optimum eGFR and ACR thresholds exceeded those of commonly advocated public health screening measures, such as LDL cholesterol and fasting blood glucose, with body mass index appearing in the third round, and smoking and LDL cholesterol in the fourth. In a tree permitting dichotomizing variables, the ACR, systolic blood pressure, and glucose first appeared in the third round, with eGFR, smoking, and LDL in the fourth. Thus, the albumin-creatinine ratio and eGFR may be at least as efficient for survival-based clinical triage as most other classic risk factors.

Association of estimated glomerular filtration rate and albuminuria with all-cause and cardiovascular mortality in general population cohorts: a collaborative meta-analysis

BACKGROUND

Substantial controversy surrounds the use of estimated glomerular filtration rate (eGFR) and albuminuria to define chronic kidney disease and assign its stages. We undertook a meta-analysis to assess the independent and combined associations of eGFR and albuminuria with mortality.

METHODS

In this collaborative meta-analysis of general population cohorts, we pooled standardised data for all-cause and cardiovascular mortality from studies containing at least 1000 participants and baseline information about eGFR and urine albumin concentrations. Cox proportional hazards models were used to estimate hazard ratios (HRs) for all-cause and cardiovascular mortality associated with eGFR and albuminuria, adjusted for potential confounders.

FINDINGS

The analysis included 105,872 participants (730,577 person-years) from 14 studies with urine albumin-to-creatinine ratio (ACR) measurements and 1,128,310 participants (4,732,110 person-years) from seven studies with urine protein dipstick measurements. In studies with ACR measurements, risk of mortality was unrelated to eGFR between 75 mL/min/1.73 m(2) and 105 mL/min/1.73 m(2) and increased at lower eGFRs. Compared with eGFR 95 mL/min/1.73 m(2), adjusted HRs for all-cause mortality were 1.18 (95% CI 1.05-1.32) for eGFR 60 mL/min/1.73 m(2), 1.57 (1.39-1.78) for 45 mL/min/1.73 m(2), and 3.14 (2.39-4.13) for 15 mL/min/1.73 m(2). ACR was associated with risk of mortality linearly on the log-log scale without threshold effects. Compared with ACR 0.6 mg/mmol, adjusted HRs for all-cause mortality were 1.20 (1.15-1.26) for ACR 1.1 mg/mmol, 1.63 (1.50-1.77) for 3.4 mg/mmol, and 2.22 (1.97-2.51) for 33.9 mg/mmol. eGFR and ACR were multiplicatively associated with risk of mortality without evidence of interaction. Similar findings were recorded for cardiovascular mortality and in studies with dipstick measurements.

INTERPRETATION

eGFR less than 60 mL/min/1.73 m(2) and ACR 1.1 mg/mmol (10 mg/g) or more are independent predictors of mortality risk in the general population. This study provides quantitative data for use of both kidney measures for risk assessment and definition and staging of chronic kidney disease.

FUNDING

Kidney Disease: Improving Global Outcomes (KDIGO), US National Kidney Foundation, and Dutch Kidney Foundation.