Microalbuminuria in the US population: third National Health and Nutrition Examination Survey

Inclusion of albuminuria in hypertension and heart guidelines

The current recommendations by all United States guideline committees, including the American Diabetes Association and the JNC 7, include screening for microalbuminuria in those with diabetes or evidence of kidney disease, but not the general population. Internationally, both the Canadian and European Guidelines have concurred with this approach. This recommendation is due in part to the findings from long-term outcome studies that measurement of microalbuminuria, while a strong predictor of cardiovascular risk, fails to shows change in CV events if reduced. Unfortunately, this conclusion may be wrong because no randomized trial has examined the question of whether a reduction in microalbuminuria does correlate with a reduction in CV events. Thus, we don't know the answer to this question. Additionally, a recent cost-effective analysis was just published, suggesting it is not worth measuring urinary albumin because it is too expensive for the information obtained. Unfortunately, these conclusions were based on the same faulty logic that relates changes in microalbuminuria to cardiovascular events. It is clear that microalbuminuria is a cardiovascular risk factor, acknowledged by both the JNC 7 and the European Guidelines. Moreover, presence of microalbuminuria correlates strongly with elevated levels of C-reactive protein and abnormal vascular responsiveness to vasodilating stimuli. Thus, its presence indicates abnormal responses by vascular tissue, perhaps due to underlying inflammatory responses. Every clinical trial that has assessed changes in albuminuria as a secondary end point with clinical outcomes has shown a strongly positive correlation between reduction in albuminuria and greater protection of a given end organ; this effect is, in part, independent of blood pressure reduction. Thus, what is needed is a clinical trial in people at high cardiovascular risk, such as those in the INVEST or ALLHAT trials where the primary end point is change in albuminuria and its relationship to cardiovascular outcomes. Likewise, a cardiovascular primary end point could relate to the secondary end point of changes in microalbuminuria, and the latter powered appropriately to make stronger statements about albuminuria and cardiovascular outcomes. With this data, guidelines can then make much strong statements about intervention on this marker of risk.

Rapid microalbuminuria screening in type 2 diabetes mellitus: simplified approach with Micral test strips and specific gravity

BACKGROUND

Microalbuminuria is known to be a harbinger of serious complications in type 2 diabetes mellitus. Since medical intervention at the onset of microalbuminuria can be critical in reducing these adverse outcomes, it is widely agreed that type 2 diabetic patients should be screened for microalbuminuria. The purpose of the present study is to evaluate Micral test strips in conjunction with a urine specific gravity determination as a rapid and accurate method for detecting microalbuminuria in type 2 diabetic patients.

METHODS

In this prospective study, a total of 444 urine samples of type 2 diabetic patients were obtained from the ABCD study cohort for analysis. Urinary albumin concentrations were determined using Micral test strips and compared to results measuring albumin by the immunoturbidimetry method of timed collections. Urine specific gravity was measured by a standard urine dipstick.

RESULTS

The performance characteristics of the Micral test strips for detecting microalbuminuria (30-300 mg albumin/24 h) were adequate but not optimal: sensitivity 88%, specificity 80%, positive predictive value 69%, negative predictive value 92%. A concomitant specific gravity determination was useful in indexing the magnitude of false negative and false positive readings by the Micral test strips.

CONCLUSIONS

While the use of Micral test strips provides a rapid approach to detecting microalbuminuria in type 2 diabetic patients, this method has limitations. The simultaneous measurement of specific gravity is helpful in addressing some of the shortcomings of this screening test.

Microalbuminuria as a marker of cardiovascular and renal risk in type 2 diabetes mellitus: a temporal perspective

Microalbuminuria is a marker for diabetic nephropathy. It also signifies cardiovascular disease, as well as nephropathy, in type 2 diabetes (DM2). Microalbuminuria may precede DM2, occurring with the insulin resistance syndrome and its components, including obesity and hypertension. Other indicators of cardiovascular risk, such as markers of inflammation, are associated with microalbuminuria in populations of patients with and without diabetes. With the rising prevalence of DM2 in minority youth, especially in Native Americans, a marker for future disease risk would allow earlier prevention strategies to be tested. Before microalbuminuria can be used in a prevention strategy, more needs to be known about the mechanism(s) of the association between elevated excretion, its relationship to glucose intolerance, and its relative contribution to cardiovascular and renal disease. These questions are especially applicable as we begin to observe the long-term complications of diabetes in youth.

New insights into the significance of microalbuminuria

PURPOSE OF REVIEW

This review summarizes recent work that has explored the association between microalbuminuria and adverse clinical outcomes in the presence and absence of diabetes.

RECENT FINDINGS

Recent investigations have documented the prevalence of microalbuminuria in the general community and have also highlighted the continuous relationship between the level of urinary albumin excretion and clinical endpoints. Even below traditional microalbuminuria thresholds, urinary albumin levels appear to correlate with clinical outcomes. Microalbuminuria is becoming increasingly recognized as an independent risk factor for cardiovascular morbidity and mortality. At least for subjects with type 2 diabetes and microalbuminuria, intensive, multifactorial interventions can reduce the risk of cardiovascular events by about 50%. Although several studies have found an association between microalbuminuria and surrogate measurements of vascular disease, the exact molecular mechanisms linking an increase in urinary albumin excretion and vascular disease are still unknown. Microalbuminuria also has a well-documented association with progressive diabetic renal disease but recent studies have suggested that the prognostic significance of microalbuminuria in this regard may not be as powerful as originally reported.

SUMMARY

Aggressive, multifactorial interventions, including the use of drugs that interrupt the renin-angiotensin system are strongly recommended for patients with diabetes and micro-albuminuria to ameliorate the progression of renal and vascular complications. This approach should also possibly apply to microalbuminuric subjects without diabetes. The relationship between microalbuminuria and progressive diabetic renal disease requires re-evaluation given temporal trends in the prevention and treatment of diabetic complications.

Ethnic differences and determinants of proteinuria among South Asian subgroups in Pakistan

BACKGROUND

Hypertension, diabetes, increasing age, and smoking are known risk factors for proteinuria. Prevalence of proteinuria is high in South Asians. However, ethnic subgroup differences and determinants of proteinuria within the South Asian population have not been explored.

METHODS

The National Health Survey of Pakistan conducted between 1990 and 1994 was used to explore ethnic subgroup variation in proteinuria. Distinct ethnic subgroups, the Muhajir, the Punjabi, the Sindhi, the Pashtun, and the Baluchi, were defined by mother tongue. We report results in individuals aged >or=15 years (N = 9442). Proteinuria was defined as dipstick positive for protein on random urine sample.

RESULTS

Increasing age, high consumption of meat, and presence of hypertension and diabetes were each independently associated with proteinuria. The age-standardized prevalence of proteinuria was 4.6% (4.2% to 5.1%) and varied among ethnic subgroups (P < 0.001). The highest was among the Sindhi (men 9.5%, women 10.3%), then the Muhajir (men 8.2%, women 4.7%), the Punjabi (men 3.2% women 3.5%), and lowest among the Baluchi (men 2.4%, women 4.2%) and the Pashtun (men 2.7%, women 1.2%). The ethnic differences persisted after adjusting for the above-mentioned sociodemographic, dietary, and clinical risk factors [adjusted odds ratio (OR) (95% CI)] were 6.42 (3.97 to 10.38) for the Sindhis, 3.58 (2.22 to 5.79) for the Muhajirs, 2.03 (1.25 to 3.29) for the Punjabis, and 1.75 (0.79 to 3.88) for the Baluchis compared to the Pashtuns).

CONCLUSION

We conclude that unmeasured environmental or genetic factors account for ethnic variations in proteinuria, and deserve further study.

Urinary albumin to osmolality ratio predicts 24-hour urine albumin excretion in diabetes mellitus

BACKGROUND

Urinary albumin to creatinine ratio (ACR) in a single urine sample has been proposed to provide an estimate of microalbuminuria by adjusting for variability in urine concentrations. We hypothesized that adjusting the urine albumin concentration of single-void specimens for actual urine osmolality (urinary albumin to osmolality ratio [AOR]) may provide a more accurate estimate of 24-hour urine albumin excretion rates (AERs).

METHODS

Patients with diabetes mellitus (DM; n = 136) had urinary concentrations of albumin, glucose, and creatinine and osmolality measured on single-void samples, and albumin levels, on 24-hour samples. Microalbuminuria is defined as an AER between 30 and 300 mg/d.

RESULTS

Correlation between AOR on single-void samples and AER on 24-hour samples (r = 0.87; P < 0.001) was similar to that between ACR and AER (r = 0.88; P < 0.001). Using a cutoff value of 18.4 mg/kg/mOsm x 10(2) (18.4 mg/mmol x 10(2)) for AOR resulted in a sensitivity and specificity of 82% and 86% in detecting microalbuminuria, respectively. The area under the curve (AUC) for AOR was 0.89. Using a cutoff value of 15.0 mg/g (1.7 mg/mmol) for ACR resulted in a sensitivity and specificity of 85% and 85% in detecting microalbuminuria, respectively. The AUC for ACR was 0.90. The ability of AOR to predict AER was maintained at varying degrees of glycosuria (glucose < 100 mg/dL [<5.5 mmol/L]; r = 0.77; 100 to 750 mg/dL [5.5 to 42 mmol/L]; r = 0.85; and >750 mg/dL [>42 mmol/L]; r = 0.92).

CONCLUSION

Urinary AOR correlates closely with 24-hour microalbuminuria determination, and the correlation is not appreciably affected by glycosuria. Thus, AOR can be used as an alternative test to ACR in the assessment of microalbuminuria in the population with DM.

Cholesterol and the risk of renal dysfunction in apparently healthy men

Despite extensive knowledge about abnormal lipid patterns in patients with end-stage renal disease, the association between cholesterol and the development of renal dysfunction is unclear. We evaluated this association in a prospective cohort study among 4,483 initially healthy men participating in the Physicians' Health Study who provided blood samples in 1982 and 1996. Main outcome measures were elevated creatinine, defined as >/= 1.5 mg/dl (133 micromol/L), and reduced estimated creatinine clearance, defined as </=55 ml/min. Cholesterol parameters included total cholesterol (<200, 200 to 239, and >/= 240 mg/dl), HDL (<40 or >/= 40 mg/dl), total non-HDL cholesterol, and the ratio of total cholesterol to HDL. We used logistic regression to calculate age- and multivariable adjusted odds ratios as a measure for the relative risk. After 14 yr, 134 men (3.0%) had elevated creatinine and 244 (5.4%) had reduced creatinine clearance. The multivariable relative risk for elevated creatinine was 1.77 (95% confidence interval [CI], 1.10 to 2.86) for total cholesterol >/= 240 mg/dl, 2.16 (95% CI, 1.42 to 3.27) for HDL <40 mg/dl, 2.34 (95% CI, 1.34 to 4.07) for the highest quartile of total cholesterol/HDL ratio (>/= >6.8), and 2.16 (95% CI, 1.22 to 3.80) for the highest quartile of non-HDL cholesterol (>/= 196.1). Similar although smaller associations were observed between cholesterol parameters and reduced creatinine clearance. Elevated total cholesterol, high non-HDL cholesterol, a high ratio of total cholesterol/HDL, and low HDL in particular were significantly associated with an increased risk of developing renal dysfunction in men with an initial creatinine <1.5 mg/dl.

Kidney function in older people: pathology, assessment and management

It is commonly not appreciated that kidney failure is predominantly a disease of older people and that the use of renal replacement therapy (RRT) amongst these patients is increasing rapidly. It is still unclear whether the decline in kidney function with increasing age represents pathology or is part of the normal ageing process. Conventional laboratory approaches to the assessment of kidney function in older people are inadequate, but the use of calculated clearance formulae and serum cystatin C can enable the earlier detection of chronic kidney disease (CKD) in this population. This could facilitate treatment aimed at reducing the progression of kidney disease in older people and improved management of its secondary complications.

Hypertension and renal dysfunction: NHANES III

The incidence rate of end-stage renal disease has increased in many countries in the past 20 yr, including the United States and Singapore. The increase in ESRD incidence in the United States is primarily attributable to diabetes and to hypertension. In Singapore the major cause of ESRD is diabetes, however the prevalence of hypertension in the Singapore population is rising rapidly, and renal complications of hypertension may become more common in the future. Information on the association of hypertension with renal dysfunction and ESRD in the United States may be useful in predicting future trends in the incidence of ESRD due to hypertension in Singapore. This paper describes published and unpublished data presented at a conference to assist in developing plans for a comprehensive renal disease prevention program in Singapore. It compares recent data on the reported prevalence of hypertension in the United States and Singapore; and presents information on the association of hypertension with serum creatinine, urinary albumin excretion, and ESRD in the United States.

Serum cystatin C in the aged: relationships with health status

BACKGROUND

Serum cystatin C (Cys C) is claimed to be superior to serum creatinine (Cr) in estimating glomerular filtration rate, but its utility in assessing renal function in the polymorbid elderly needs to be evaluated.

METHODS

In a cross-sectional, community-based survey performed in Lieto in southwestern Finland, Cys C, Cr, and urinary albumin-creatinine ratio (ACR) were measured in 1,260 subjects aged 64 to 100 years. Associations of demographic characteristics and health status factors with levels of Cys C, Cr, and ACR were assessed by means of linear models.

RESULTS

In men, hypertension, coronary heart disease, urinary infection, rheumatoid arthritis, glucocorticoid treatment, older age, and lower functional status were found to be significant predictors of higher Cys C values, whereas hypertension, coronary heart disease, urinary infection, older age, and increasing body mass index (BMI) significantly predicted higher Cr values. Among women, corresponding factors were hypertension, glucocorticoid treatment, age, functional status, and BMI for Cys C and hypertension, BMI, and age for Cr. Diabetes was significantly associated only with ACR. These factors explained 35% of variation in Cys C values in men and 34.5% in women versus only 14.8% and 11.3% for Cr, respectively.

CONCLUSION

Glucocorticoid treatment was recognized as an independent Cys C-increasing factor, presumably nonglomerular. In comparison with Cys C, a considerably greater proportion of total variation in Cr values seems to be explained by extrarenal factors.

Early detection of kidney disease in community settings: the Kidney Early Evaluation Program (KEEP)

BACKGROUND

Early identification of persons at risk for kidney disease provides an opportunity to prevent or delay its progression and decrease morbidity and mortality. Our hypothesis was that implementation of a targeted screening program in communities with high-risk populations would detect previously unidentified persons with or at high risk for chronic kidney disease (CKD) with a prevalence that exceeds that predicted for CKD in the general population.

METHODS

Persons with hypertension or diabetes or a first-order relative with hypertension, diabetes, or kidney disease were screened for kidney disease risk factors. Blood pressure, blood glucose level, serum creatinine level, hemoglobin level, microalbuminuria, hematuria, pyuria, body mass index, and estimated glomerular filtration rate (EGFR) were evaluated.

RESULTS

Six thousand seventy-one eligible persons were screened from August 2000 through December 2001: of these persons, 68% were women, 43% were African American, 36% were white, 10% were Hispanic, and 5% were Native American. Most reported high-school education or more (84%) and health insurance coverage (86%). Twenty-seven percent met the screening definitions for diabetes; 64%, for hypertension; 29%, for microalbuminuria; 8%, for anemia; 18%, for hematuria; 13%, for pyuria; 5%, for elevated serum creatinine level; 16%, for reduced EGFR; and 44%, for obesity. Among participants without a reported history of specified conditions, screening identified 82 participants (2%) with diabetes, 1,014 participants (35%) with hypertension, 277 participants (5%) with elevated serum creatinine levels, 839 participants (14%) with reduced EGFRs, and 1,712 participants (29%) with microalbuminuria. Thirty-five percent of participants with a history of diabetes had elevated serum glucose levels at screening (> or =180 mg/dL [10 mmol/L]), and 64% with a history of hypertension did not have blood pressure controlled to less than 140/90 mm Hg. Only 18% of participants with a history of diabetes and 31% with a reduced EGFR had blood pressure controlled to less than 130/80 mm Hg and less than 135/85 mm Hg, respectively.

CONCLUSION

Targeted screening is effective in identifying persons with previously unidentified or poorly controlled kidney disease risk factors, as well as persons with a moderately decreased EGFR.

Regression of albuminuria: latest evidence for a new approach

OBJECTIVE

To review the latest studies on antihypertensive strategies in the treatment of microalbuminuria, in order to highlight the association of microalbuminuria with hypertension and type 2 diabetes, the evidence for microalbuminuria as a risk factor for target-organ damage and mortality, and the prognostic significance of regression of microalbuminuria.

STUDY SELECTION

Randomized controlled trials in patients with hypertension, type 2 (non-insulin-dependent) diabetes mellitus and microalbuminuria, with changes in albumin excretion rate (AER) as a primary outcome measure.

RESULTS OF DATA ANALYSIS

Antihypertensive treatment is the most effective method for reducing microalbuminuria. Although microalbuminuria regression is related to reduction in blood pressure, antihypertensive drugs acting on the renin-angiotensin system have an antiproteinuric effect that is additional to that of blood pressure reduction. The combination of these agents with diuretics, even when used in low doses, may further reduce AER in these patients.

CONCLUSIONS

Blockade of the renin-angiotensin system with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers is a most effective means of treating microalbuminuria and preventing its progression to overt nephropathy and, perhaps, the associated cardiovascular disease. The effect of this strategy may be improved further with the use, as first-line treatment, of a combination of angiotensin-converting enzyme inhibitor and diuretic.

Prevalence of hematuria among Zuni Indians with and without diabetes: The Zuni kidney Project

BACKGROUND

There is an epidemic of kidney disease among the Zuni Indians. In contrast to other American Indian tribes, the epidemic among the Zuni Indians is attributable to diabetic and nondiabetic renal disease.

METHODS

The Zuni Kidney Project, established to reduce the burden of renal disease, conducted a population-based cross-sectional survey of Zuni Indians aged 5 years or older to precisely estimate the prevalence of hematuria. The survey used neighborhood household clusters as the sampling frame to maximize ascertainment and minimize bias. During the survey, we administered a questionnaire; collected blood and urine samples; and measured blood pressure, height, and weight.

RESULTS

Age and sex distributions in our sample (n = 1,469) were similar to those of the eligible Zuni population (n = 9,228). Prevalences of hematuria, defined as dipstick of trace or greater and 50 red blood cells/microL or greater, age- and sex-adjusted to the Zuni population aged 5 years or older, were 33.2% (95% confidence interval [CI], 30.7 to 35.6) and 17.8% (95% CI, 15.8 to 19.8), respectively. Hematuria of trace or greater was more common among females (40.6%; 95% CI, 37.0 to 44.1) than males (25.1%; 95% CI, 21.8 to 28.4). Hematuria of trace or greater was common among Zuni Indians without diabetes (females, 39.7%; 95% CI, 35.7 to 43.8; males, 22.7%; 95% CI, 19.4 to 26.1) and with diabetes (females, 47.5%; 95% CI, 39.8 to 55.2; males, 45.8%; 95% CI, 34.3 to 57.3). Diabetes and alcohol use for greater than 10 years were associated with hematuria among males, but not females.

CONCLUSION

The prevalence of hematuria is high among Zuni Indians with and without diabetes. These findings are consistent with the hypothesis that nondiabetic kidney disease is common among Zuni Indians with and without diabetes.

Microalbuminuria in hypertension

A body of evidence indicates that microalbuminuria is a well-recognized marker of cardiovascular complications and increased cardiovascular risk in hypertension. However, the prognostic significance of microalbuminuria remains controversial because only the results of a few prospective studies performed in small groups of hypertensive subjects without diabetes mellitus are available. Several factors can affect the prevalence of microalbuminuria in hypertension including age, sex, race, severity of the disease, and concomitant risk factors. This accounts for the large differences in the prevalence of microalbuminuria that can be found in the literature, with prevalence rates going from a low of 4.7% to a high of 46%. The main determinant of albumin excretion rate in subjects with mild hypertension and no cardiovascular complications seems to be the hemodynamic load, whereas in subjects with more severe hypertension and associated target organ damage, the augmented urinary albumin leak is probably the consequence of glomerular damage. Inhibition of the renin-angiotensin system with angiotensin-converting enzyme inhibitors or angiotensin II receptor antagonists is particularly effective at reducing the albumin excretion rate, but whether these classes of drugs are more beneficial in patients with microalbuminuria remains to be determined. There is general consensus that evaluation of microalbuminuria is useful for the assessment of overall cardiovascular risk in hypertension, since albumin excretion rate appears to be a cost-effective way to identify patients at higher risk for whom additional preventive and therapeutic measures are advisable.

Cardiovascular risk factors are differently associated with urinary albumin excretion in men and women

Cardiovascular morbidity and mortality is not equally distributed among genders, men being more affected than women. It is not clear whether this is only related to a higher prevalence of the cardiovascular risk factors or to a similar prevalence of the risk factors as in women but a greater vascular susceptibility to these risk factors in men. This was tested by studying the association between various cardiovascular risk factors and urinary albumin excretion (UAE) in a large cohort of male and female subjects. While the prevalence of smoking and hypercholesterolemia was comparable between the genders, obesity was more common in women, and diabetes and hypertension were more frequent in men. The prevalence of microalbuminuria was about twofold higher in men. Interestingly, for a given level of any risk factor, UAE was higher in men than in women. On multivariate analysis with UAE as the dependent variable, an interaction with gender was found for the risk factors age, body mass index, and plasma glucose. Thus, for a higher age, body mass index, and glucose, the UAE is significantly increased in men when compared with women. It is concluded that gender differences exist in the association between cardiovascular risk factors and UAE. This is consistent with a larger vascular susceptibility to these risk factors in men as compared with women.

Epidemic of diabetic and nondiabetic renal disease among the Zuni Indians: the Zuni Kidney Project

There is an epidemic of renal disease among the Zuni Indians. The prevalence of end-stage renal disease among the Zuni Indians is 18.4-fold and 7.4-fold higher than among European Americans and American Indians/Alaskan Natives, respectively. In contrast to other American Indian tribes, nondiabetic renal disease accounts for a significant percent of the renal disease burden among the Zuni Indians. To explore this hypothesis, a community epidemiologic study of the Zuni Pueblo was conducted. A questionnaire was administered, blood and urine samples were collected, and BP, height, and weight were measured. Neighborhood household clusters were used as the sampling frame to maximize ascertainment and minimize bias. Age and gender distributions in the sample (n = 1483) were similar to those of the eligible Zuni population (n = 9228). The prevalence, age-adjusted and gender-adjusted to the Zuni population, of incipient (0.03 < or = UACR < 0.3) albuminuria (IA) (15.0% [95% confidence interval, 13.1 to 16.9%]), and overt (UACR > or = 0.3) albuminuria (OA) (4.7% [3.6 to 5.8%]) was high. The prevalence estimates for IA and OA were higher among diabetic participants (IA: 33.6% [27.6 to 39.7%]; OA: 18.7% [13.7 to 23.7%]) than nondiabetic participants (IA: 10.8% [9.0 to 12.6%]; OA: 1.8% [1.0 to 2.5%]). However, there were more nondiabetic participants; therefore, they comprised 58.0% [51.4 to 64.6%] and 30.9% [20.0 to 41.7%] of participants with IA and OA, respectively. In contrast to most other American Indian tribes, nondiabetic renal disease contributes significantly to the overall burden of renal disease among the Zuni Indians.

Microalbuminuria in critically ill medical patients: prevalence, predictors, and prognostic significance

OBJECTIVE

To ascertain the prevalence, predictors, and prognostic significance of microalbuminuria in critically ill patients.

DESIGN

Prospective cohort study.

SETTING

Medical intensive care unit of a community teaching hospital.

PATIENTS

Admitted critically ill patients.

MEASUREMENTS AND MAIN RESULTS

We measured serial spot urine albumin-creatinine ratios in 104 critically ill patients, with a median age of 64.5 yrs and median Acute Physiology and Chronic Health Evaluation (APACHE) II and Sequential Organ Failure Assessment (SOFA) scores of 20.5 and 5.0, respectively. Sixty-nine percent of the patients had microalbuminuria or clinical proteinuria and 43.3% had an albumin-creatinine ratio >/=100 mg/g at admission. The acuity of illness, being non-White, and having diabetes mellitus were independent predictors of albumin-creatinine ratio >/=100 mg/g. The overall mortality rate was 26.9% (28/104). Patients with an albumin-creatinine ratio >/=100 mg/g were 2.7 times as likely to die compared with those with an albumin-creatinine ratio <100 mg/g, even after simultaneous adjustments for age, and APACHE II and SOFA scores (odds ratio, 2.7; 95% confidence interval, 1.1-7.2, p =.04). The association of albumin-creatinine ratio >/=100 mg/g with death was consistent across age, ethnicity, renal function, acuity of illness, and comorbid conditions. Among survivors, patients with an albumin-creatinine ratio >/=100 mg/g stayed approximately 5 days longer in the hospital (p =.0007). Overall, the albumin-creatinine ratio shared similar predictive characteristics with APACHE II and SOFA scores.

CONCLUSIONS

This study confirms a high prevalence of microalbuminuria in critically ill patients and suggests that an albumin-creatinine ratio >/=100 mg/g is an independent predictor of mortality and hospital stay.

Association of dietary protein intake and microalbuminuria in healthy adults: Third National Health and Nutrition Examination Survey

BACKGROUND

The relationship between dietary protein intake (DPI) and microalbuminuria (MA) is unclear. We investigated whether DPI was associated with urinary albumin level in a population sample of persons with normal kidney function.

METHODS

We addressed this question in adults aged 20 to 80 years from the Third National Health and Nutrition Examination Survey (n = 12,422). DPI was assessed from a 24-hour dietary recall and quantified as percentage of total energy intake. MA is defined as urinary albumin-creatinine ratio 30 mg/g (3 mg/mmol) or greater.

RESULTS

In multivariable logistic regression models adjusted for sociodemographic characteristics and coronary heart disease risk factors, DPI was not associated with MA in normotensive or nondiabetic persons. In crude models, odds ratios (ORs) for MA were 1.9 (95% confidence interval, 1.2 to 3.0) in persons with hypertension (n = 3,433) and 2.4 (95% confidence interval, 1.1 to 5.2) in those with diabetes (n = 1,165) in the highest (>19%) versus lowest (<11.7%) quintile of DPI. However, in models adjusted for the concurrent prevalence of diabetes or hypertension, this association attenuated to nonsignificance. Persons in the highest quintile of DPI who had both hypertension and diabetes (n = 634) had a significantly elevated OR for MA (3.3; 95% confidence interval, 1.4 to 7.8) compared with those in the lowest quintile.

CONCLUSION

DPI is not associated with MA in healthy persons or those with isolated hypertension or diabetes. However, in persons with both conditions, high DPI is associated with increased prevalence of MA. These findings suggest the need for further research on weight-loss strategies for high-risk persons.

Prevalence of chronic kidney disease and decreased kidney function in the adult US population: Third National Health and Nutrition Examination Survey

BACKGROUND

Recently developed clinical practice guidelines and calibration of the Third National Health and Nutrition Examination Survey (NHANES III) serum creatinine assay provide a basis for estimating the prevalence and distribution of chronic kidney disease (CKD) in the United States using standardized criteria based on estimated glomerular filtration rate (GFR) and persistent albuminuria.

METHODS

A nationally representative sample of 15,625 noninstitutionalized adults aged 20 years and older from the NHANES III was analyzed. Kidney function (GFR), kidney damage (albuminuria), and stages of CKD (GFR and albuminuria) were estimated from calibrated serum creatinine level, spot urine albumin level, age, sex, and race. GFR was estimated using the simplified Modification of Diet in Renal Disease Study equation and compared with the Cockcroft-Gault equation for creatinine clearance (CCr).

RESULTS

The prevalence of CKD in the US adult population was 11% (19.2 million). By stage, an estimated 5.9 million individuals (3.3%) had stage 1 (persistent albuminuria with a normal GFR), 5.3 million (3.0%) had stage 2 (persistent albuminuria with a GFR of 60 to 89 mL/min/1.73 m(2)), 7.6 million (4.3%) had stage 3 (GFR, 30 to 59 mL/min/1.73 m(2)), 400,000 individuals (0.2%) had stage 4 (GFR, 15 to 29 mL/min/1.73 m(2)), and 300,000 individuals (0.2%) had stage 5, or kidney failure. Aside from hypertension and diabetes, age is a key predictor of CKD, and 11% of individuals older than 65 years without hypertension or diabetes had stage 3 or worse CKD. Compared with GFR estimates, CCr estimates showed a steeper decline with age and were lower in non-Hispanic blacks.

CONCLUSION

CKD is common and warrants improved detection and classification using standardized criteria to improve outcomes. Am J Kidney Dis 41:1-12.

Kidney disease, genotype and the pathogenesis of vasculopathy

PURPOSE OF REVIEW

The two leading causes of end-stage renal disease in the United States are diabetes mellitus and hypertensive nephrosclerosis, accounting for over two-thirds of all cases. In many patients both diseases are associated with small- and large-vessel disease, commonly attributed to hypertension or accelerated atherosclerosis. Recent investigations, however, have suggested that renal large-vessel and microvascular disease may be independent contributors to progressive kidney failure.

RECENT FINDINGS

Although genes have not been definitely linked to renal vascular disease, population- and family-based epidemiology of kidney disease, segregation analysis of Pima and Caucasian families in which diabetic nephropathy is clustered, and the positional cloning of genes responsible for rare, familial glomerulosclerosis syndromes support the hypothesis that genes regulate the pathogenesis of renal disease. This review highlights developments in our current understanding of vasculopathy and its role in renal disease, and it summarizes evidence suggesting that genetic determinants for the vascular phenotype are associated with common causes of chronic renal failure.

SUMMARY

With the application of genomics and proteomics methodologies to drug discovery, the identification of renal susceptibility genes should identify new mechanisms of progressive renal disease pathogenesis and generate novel target molecules for the treatment of kidney disease.

Microalbuminuria, cardiovascular, and renal risk in primary hypertension

Microalbuminuria is defined as abnormal urinary excretion of albumin between 30 and 300 mg/d. It can be measured accurately by several widely available and sensitive methods. This abnormality can be found in 8 to 15% of nondiabetic patients with primary hypertension, although its prevalence varies greatly in the literature, likely due to differences in the methods used to detect it and to the criteria applied in the selection of patients. The pathogenetic mechanisms leading to the development of microalbuminuria are still not completely known. BP load and increased systemic vascular permeability, possibly due to early endothelial damage, seem to play a major role. Increased urinary albumin excretion has been associated with several unfavorable metabolic and nonmetabolic risk factors and subclinical hypertensive organ damage. In fact, a higher prevalence of concentric left ventricular hypertrophy and subclinical impairment of left ventricular performance, as well as the presence of carotid atherosclerosis, have been reported in patients with microalbuminuria. These associations might per se justify a greater incidence of cardiovascular events. Long-term longitudinal studies have recently confirmed the unfavorable prognostic significance of microalbuminuria in hypertensive patients. It has also been hypothesized that microalbuminuria might be a forerunner of overt renal damage in primary hypertension. Clinical studies, however, have shown conflicting results, and this hypothesis has to be considered tempting but speculative at present. In conclusion, microalbuminuria is a specific, integrated marker of cardiovascular risk and target organ damage in primary hypertension and one that is suitable for identifying patients at higher global risk. A wider use of this test in the diagnostic work-up of hypertensive patients is recommended.

Chronic kidney disease in the United States: an underrecognized problem

The continued growth of the population with end-stage renal disease (ESRD) is partially related to the underrecognition of earlier stages of chronic kidney disease (CKD) and risk factors for the development of CKD. There are several published estimates of the prevalence of CKD in the United States. From Third National Health and Nutrition Examination Survey data it has been estimated that there are 6.2 million individuals with serum creatinine levels at or above 1.5 mg/dL, or 8.3 million individuals with decreased glomerular filtration rate (<60 mL/min/1.73 m (2)). Estimates of prevalence from a health maintenance organization study suggest that there are 4.2 million Americans with persistently elevated serum creatinine levels. In addition to the high prevalence, several studies have shown that CKD is associated with increased risk for cardiovascular disease, hospitalizations, and mortality. To promote earlier detection of CKD, The National Kidney Foundation Guidelines for CKD: Evaluation, Classification and Stratification, recommended screening individuals at increased risk for CKD, such as patients with diabetes, high blood pressure, and family history of kidney disease. Therapeutic interventions to delay progression and reduce comorbidity, such as cardiovascular disease, are more likely to be effective if they are implemented early in the course of CKD.