Octogenarians and nonagenarians starting dialysis in the United States.

BACKGROUND: The elderly constitute the fastest-growing segment of the end-stage renal disease (ESRD) population, but the epidemiology and outcomes of dialysis among the very elderly, that is, those 80 years of age and older, have not been previously examined at a national level. OBJECTIVE: To describe recent trends in the incidence and outcomes of octogenarians and nonagenarians starting dialysis. DESIGN: Observational study. SETTING: U.S. Renal Data System, a comprehensive, national registry of patients with ESRD. PARTICIPANTS: Octogenarians and nonagenarians initiating dialysis between 1996 and 2003. MEASUREMENTS: Rates of dialysis initiation and survival. RESULTS: The number of octogenarians and nonagenarians starting dialysis increased from 7054 persons in 1996 to 13,577 persons in 2003, corresponding to an average annual increase in dialysis initiation of 9.8%. After we accounted for population growth, the rate of dialysis initiation increased by 57% (rate ratio, 1.57 [95% CI, 1.53 to 1.62]) between 1996 and 2003. One-year mortality for octogenarians and nonagenarians after dialysis initiation was 46%. Compared with octogenarians and nonagenarians initiating dialysis in 1996, those starting dialysis in 2003 had a higher glomerular filtration rate and less morbidity related to chronic kidney disease but no difference in 1-year survival. Clinical characteristics strongly associated with death were older age, nonambulatory status, and more comorbid conditions. LIMITATIONS: Survival of patients with incident ESRD who did not begin dialysis could not be assessed. CONCLUSIONS: The number of octogenarians and nonagenarians initiating dialysis has increased considerably over the past decade, while overall survival for patients on dialysis remains modest. Estimates of prognosis based on patient characteristics, when considered in conjunction with individual values and preferences, may aid in dialysis decision making for the very elderly.

The metabolic syndrome and chronic kidney disease.

PURPOSE OF REVIEW: The metabolic syndrome is a constellation of physical and laboratory abnormalities including hypertension, hyperglycemia, hyperlipidemia and abdominal obesity. Over the past decade, the metabolic syndrome has emerged as a critically important risk factor for cardiovascular disease. RECENT FINDINGS: A large population-based cross-sectional analysis (the National Health and Nutrition Evaluation Survey III) found that the presence of the metabolic syndrome was associated with chronic kidney disease, defined as an estimated glomerular filtration rate of less than 60 ml/min per 1.73 m and was also associated with proteinuria. More recently, a prospective cohort study found that the presence of the metabolic syndrome was associated with incident chronic kidney disease by the same definition, even when excluding individuals with diabetes mellitus and hypertension. More studies are required to determine whether the relationship between the metabolic syndrome and chronic kidney disease is mainly mediated by hyperglycemia (with insulin resistance) and hypertension, or other metabolic or hemodynamic factors. SUMMARY: The metabolic syndrome is associated with chronic kidney disease. Efforts aimed at determining the mechanisms underlying this association and strategies for the prevention of chronic kidney disease (or slowing the progression of chronic kidney disease) in affected patients should be research priorities in the future.

Correlates and outcomes of dementia among dialysis patients: the Dialysis Outcomes and Practice Patterns Study.

BACKGROUND: Recent studies suggest a high prevalence of cognitive impairment and dementia in persons with end-stage renal disease (ESRD), yet risk factors for dementia and its prognostic significance in persons with ESRD remain unclear. The goals of this study were to determine the prevalence, correlates and dialysis-related outcomes of dementia in an international sample of haemodialysis patients. METHODS: We analysed data collected from a cohort of 16 694 patients in the Dialysis Outcomes and Practice Patterns Study. Dementia was defined as a diagnosis of dementia documented in the medical record. We used logistic regression to determine the baseline correlates of dementia and Cox proportional hazards models to determine the relative risk (RR) of death and dialysis withdrawal for patients with dementia, while adjusting for a number of confounding factors. RESULTS: Overall, 4% of the cohort had a recorded diagnosis of dementia. In the cross-sectional analyses, risk factors for dementia in the general population including age, black race, low educational attainment, cerebrovascular disease and diabetes, as well as modifiable uraemia-related factors, including markers of malnutrition and anaemia, were independently associated with dementia. After adjustment for a number of confounding factors, dementia was associated with an increased risk of death [RR 1.48, 95% confidence interval (CI) 1.32-1.66] and dialysis withdrawal (RR 2.01, 95% CI 1.57-2.57). CONCLUSIONS: Dementia is associated with adverse outcomes among ESRD patients. Dialysis providers should consider instituting routine screening for cognitive impairment among elderly patients in order to identify those at risk for associated adverse outcomes.

Systemic inflammatory markers, periodontal diseases, and periodontal infections in an elderly population.

OBJECTIVES: To study the levels of systemic markers for inflammation with parameters of periodontal diseases in older people. DESIGN: A cross-sectional study was conducted in a cohort that is being followed prospectively on the effects of aging and body composition on morbidity. SETTING: University of Pittsburgh, Pittsburgh, and University of Tennessee, Memphis. PARTICIPANTS: One thousand one hundred thirty-one participants (mean age+/-standard deviation 72.7+/-2.8); 66% white and 50% male. MEASUREMENTS: Periodontal examination, including probing depth and attachment loss, was performed. Periodontal disease extent was divided into 0% of sites with probing depth of 6 mm or more, 1% to 10% of sites with probing depth of 6 mm or more and more than 10% of sites with probing depth of 6 mm or more. Subgingival plaque samples were collected from four molar teeth, and the levels of periodontal pathogens were determined using the benzoyl-DL-arginine-naphthylamide (BANA) test. Plasma interleukin-6 (IL-6), C-reactive protein (CRP), plasminogen activator inhibitor type-1 (PAI-1), and tumor necrosis factor alpha (TNF-alpha) levels were measured in all participants. Assessments of risk factors associated with elevated levels of markers of systemic inflammation were also determined. Multiple regression analysis was employed to analyze the data. RESULTS: IL-6 levels were significantly higher in participants with more-extensive periodontal disease than in other participants. Periodontal disease extent was significantly associated with higher TNF-alpha plasma levels, controlling for established risk factors for elevated TNF-alpha levels. Participants with BANA-positive species had significantly higher CRP plasma levels when controlling for risk factors for elevated CRP levels. CONCLUSION: Periodontal disease and infection may be modifiable risk indicators for elevated levels of systemic inflammatory markers in older people.

Self-assessed sleep quality in chronic kidney disease.

BACKGROUND: Although sleep complaints are commonly reported in persons with end stage renal disease (ESRD), little is known about the prevalence of sleep complaints in chronic kidney disease (CKD), and the relation of sleep quality to the severity of kidney disease. METHODS: We administered the Kidney Disease Quality of Life (KDQOL) sleep scale to 156 subjects, 78 with ESRD and 78 with CKD. Glomerular filtration rate (GFR) was estimated using the six variable Modification of Diet in Renal Disease (MDRD) equation and used to stratify subjects with CKD as mild-moderate (GFR >25 ml/min/1.73 m(2)) and advanced (GFR <25 ml/min/1.73 m(2)). We used multivariable linear regression to determine independent predictors of KDQOL sleep scale scores. Higher scores indicate higher self-reported quality of sleep. RESULTS: Median scores on the KDQOL sleep scale were 59 (interquartile range 40-80) in subjects with ESRD and 69 (interquartile range 53-80) in subjects with CKD (P=0.04). Thirty-four percent of subjects with ESRD, 27% of subjects with advanced CKD, and 14% of subjects with mild to moderate CKD had sleep maintenance disturbances (P=0.05). Thirteen percent of subjects with ESRD, 11% of subjects with advanced CKD, and no subjects with mild-moderate CKD had complaints of daytime somnolence (P=0.03). There was no significant difference in the prevalence of sleep adequacy complaints in persons with ESRD versus CKD. In multivariable analyses, only age and ESRD status (vs. CKD) were significant predictors of lower KDQOL sleep scores. Among subjects with CKD, there was a significant direct association between estimated GFR and scores on the KDQOL sleep scale in non-African American subjects (P=0.01). CONCLUSIONS: Sleep complaints are common in persons with CKD and ESRD and may be associated with the severity of kidney disease.

Chronic kidney disease and cognitive impairment in the elderly: the health, aging, and body composition study.

Previous studies suggest a link between chronic kidney disease (CKD) and cognitive impairment. Whether the longitudinal course of cognitive impairment differs among people with or without CKD is unknown. Data collected in 3034 elderly individuals who participated in the Health, Aging, and Body Composition study were analyzed. Cognitive function was assessed with the Modified Mini-Mental State Exam (3MS) at baseline and then 2 and 4 yr after baseline. Cognitive impairment was defined as a 3MS score <80 or a decline in 3MS >5 points after 2 or 4 yr of follow-up among participants with baseline 3MS scores > or =80. Participants with CKD, defined as an estimated GFR (eGFR) <60 ml/min per 1.73 m2, were further divided into two eGFR strata. Unadjusted mean baseline 3MS scores and mean declines in 3MS scores over 4 yr were significantly more pronounced for participants with lower baseline eGFR. More advanced stages of CKD were associated with an increased risk for cognitive impairment: Odds ratio (OR) 1.32 (95% confidence interval [CI] 1.03 to 1.69) and OR 2.43 (95% CI, 1.38 to 4.29) for eGFR 45 to 59 ml/min per 1.73 m2 and <45 ml/min per 1.73 m2, respectively, adjusted for case mix, baseline 3MS scores, and other potential confounders. CKD is associated with an increased risk for cognitive impairment in the elderly that cannot be fully explained by other well-established risk factors. Studies aimed at understanding the mechanism(s) responsible for cognitive impairment in CKD and efforts to interrupt this decline are warranted.

Metabolic syndrome and the risk for chronic kidney disease among nondiabetic adults.

The metabolic syndrome is a risk factor for the development of diabetes and cardiovascular disease; however, no prospective studies have examined the metabolic syndrome as a risk factor for chronic kidney disease (CKD). A total of 10,096 nondiabetic participants who were in the Atherosclerosis Risk in Communities study and had normal baseline kidney function composed the study cohort. The metabolic syndrome was defined according to recent guidelines from the National Cholesterol Education Program. Incident CKD was defined as an estimated GFR (eGFR) <60 ml/min per 1.73 m2 at study year 9 among those with an eGFR > or =60 ml/min per 1.73 m2 at baseline. After 9 yr of follow-up, 691 (7%) participants developed CKD. The multivariable adjusted odds ratio (OR) of developing CKD in participants with the metabolic syndrome was 1.43 (95% confidence interval [CI], 1.18 to 1.73). Compared with participants with no traits of the metabolic syndrome, those with one, two, three, four, or five traits of the metabolic syndrome had OR of CKD of 1.13 (95% CI, 0.89 to 1.45), 1.53 (95% CI, 1.18 to 1.98), 1.75 (95% CI, 1.32 to 2.33), 1.84 (95% CI, 1.27 to 2.67), and 2.45 (95% CI, 1.32 to 4.54), respectively. After adjusting for the subsequent development of diabetes and hypertension during the 9 yr of follow-up, the OR of incident CKD among participants with the metabolic syndrome was 1.24 (95% CI, 1.01 to 1.51). The metabolic syndrome is independently associated with an increased risk for incident CKD in nondiabetic adults.

Frequent hemodialysis and psychosocial function.

Studies suggest that more frequent hemodialysis (HD; short daily and long nocturnal dialysis) may be associated with a variety of clinical benefits, including improvement in blood pressure, anemia, and hyperphosphatemia, regression of left ventricular hypertrophy, and reduced rates of hospitalization. Whether these clinical benefits are paralleled by improvements in health-related quality of life (HRQOL) has been unclear. In addition, the psychosocial burden of more intensive HD schedules has not been critically evaluated. Recent reports have suggested beneficial effects of frequent HD on global HRQOL, dialysis-related and uremic symptoms, patient satisfaction, and psychosocial burden. However, the interpretation of many of these studies is restricted by limitations in study design, follow-up, and generalizability. This article reviews the current literature focusing on psychosocial and HRQOL effects of frequent HD and suggests future directions for research in this important area.

Dialysis session length ("t") as a determinant of the adequacy of dialysis.

Several studies have shown an association between the hemodialysis session length (the t of Kt or Kt/V) and favorable outcomes for patients on maintenance hemodialysis. In a single randomized controlled trial that systematically varied hemodialysis session length, shorter session length was associated with an increased risk for morbidity and mortality, independent of the time-averaged concentration of urea. Observational studies of dialysis session length have yielded conflicting results, although virtually all studies have confounded hemodialysis session length with hemodialysis efficiency or dose. Limited observational data from nocturnal hemodialysis programs more strongly suggest an independent beneficial effect of longer session length. In aggregate, data on the effects of hemodialysis session length are inconclusive. Future studies should evaluate hemodialysis session length independent of efficiency, and should consider the evaluation of dose by using other clearance parameters and the adequacy of ultrafiltration in addition to solute kinetics.

Chronic kidney disease and cognitive impairment in menopausal women.

BACKGROUND: Although end-stage renal disease has been associated with cognitive impairment, the relation between lesser degrees of chronic kidney disease (CKD) and cognitive impairment is less well understood. METHODS: Data for 1,015 women enrolled at 10 of the 20 Heart Estrogen/Progestin Replacement Study clinical sites were analyzed. All participants were younger than 80 years and had established coronary artery disease at study entry. Participants underwent 6 standard tests of cognitive function evaluating various domains. Unadjusted, residual age- and race-adjusted, and multivariable-adjusted linear and logistic regression models were used. Glomerular filtration rate (GFR) was estimated using the Modification of Diet in Renal Disease regression equation. In addition to analyses across the spectrum of GFRs, CKD was categorized as mild (estimated GFR [eGFR], 45 to 60 mL/min/1.73 m2), moderate (eGFR, 30 to 44 mL/min/1.73 m2), and severe (eGFR, <30 mL/min/1.73 m2) according to a modification of recently established classification guidelines. RESULTS: Mean eGFR was 57 +/- 14 mL/min/1.73 m2. In multivariable analyses, eGFR was associated significantly with impairment in global cognition, executive function, language, and memory (approximately 15% to 25% increase in risk for dysfunction/10-mL/min/1.73 m2 decrement in eGFR). Associations among eGFR and cognitive function were independent of residual effects of age and race (2 key determinants of GFR) and the contributions of education, lifestyle factors, stroke, diabetes, and other laboratory variables. CONCLUSION: CKD is associated with cognitive impairment in menopausal women with coronary artery disease.

Suicide in the United States end-stage renal disease program.

Although depression and dialysis withdrawal are relatively common among individuals with ESRD, there have been few systematic studies of suicide in this population. The goals of this study were to compare the incidence of suicide with national rates and to contrast the factors associated with suicide with those associated with withdrawal in persons with ESRD. All individuals who were aged 15 yr and older and initiated dialysis between April 1, 1995, and November 30, 2000, composed the analytic cohort. Patients were censored at the time of death, transplantation, or October 31, 2001. Death as a result of suicide in the ESRD population and the general US population was ascertained from the Death Notification Form and the Centers for Disease Control and Prevention, respectively. Standardized incidence ratios for suicide among patient subgroups were computed using national data from the year 2000 as the reference population. The crude suicide rate from 1995 to 2001 was 24.2 suicides per 100,000 patient-years, and the overall standardized incidence ratio for suicide was 1.84 (95% confidence interval, 1.50 to 2.27). In multivariable models, age > or =75 yr, male gender, white or Asian race, geographic region, alcohol or drug dependence, and recent hospitalization with mental illness were significant independent predictors of death as a result of suicide. Persons with ESRD are significantly more likely to commit suicide than persons in the general population. Although relatively rare, risk assessment can be used to identify patients for whom counseling and other interventions might be beneficial.

Validation of the Kidney Disease Quality of Life (KDQOL) cognitive function subscale.

BACKGROUND: Formal cognitive function testing is cumbersome, and no self-administered instruments for estimating cognitive function in persons with chronic kidney disease (CKD) and end-stage renal disease (ESRD) have been validated. The goal of this study was to determine the validity of the Kidney Disease Quality of Life Cognitive Function scale (KDQOL-CF) for the assessment of cognitive impairment in persons with kidney disease. METHODS: We administered the KDQOL-CF to 157 subjects, 79 with ESRD and 78 with CKD participating in a cross-sectional study of cognitive function. Scores on the Modified Mini-Mental State Exam (3MS) were considered the gold standard measure of global cognitive function. Performance characteristics of the KDQOL-CF were assessed using correlation coefficients, Bland-Altman plots, and receiver operating characteristic curves. RESULTS: Median scores on the KDQOL-CF were 73 (interquartile range 60-87) for subjects with ESRD and 87 (interquartile range 73-100) for subjects with CKD (P < 0.0001). Scores on the KDQOL-CF were directly correlated with scores on the 3MS (r = 0.31, P = 0.0001). Defining global cognitive impairment as a 3MS score < 80, a cut-point of 60 on the KDQOL-CF accurately classified 76% of subjects, with 52% sensitivity and 81% specificity. On multivariable analysis, cerebral and peripheral vascular disease, benzodiazepine use, and higher serum phosphorus concentrations were associated with lower KDQOL-CF scores, while beta blocker use, education, and higher serum albumin concentrations were associated with higher KDQOL-CF scores. CONCLUSION: The KDQOL-CF is a valid instrument for estimating cognitive function in patients with CKD and ESRD. KDQOL-CF screening followed by 3MS testing in selected individuals may prove to be an effective and efficient strategy for identifying cognitive impairment in patients with kidney disease.

Cognitive impairment in chronic kidney disease.

OBJECTIVES: To assess the prevalence of cognitive impairment in persons with chronic kidney disease (CKD) and its relation to the severity of CKD. DESIGN: Cross-sectional study. SETTING: University-affiliated ambulatory nephrology and dialysis practices. PARTICIPANTS: Eighty subjects with CKD Stages III and IV not requiring dialysis (CKD) and 80 subjects with CKD Stage V on hemodialysis (end-stage renal disease (ESRD)) with a mean age+/-standard deviation of 62.5+/-14.3. MEASUREMENTS: Three standardized cognitive tests, the Modified Mini-Mental State Examination (3MS), Trailmaking Test B (Trails B), and California Verbal Learning Trial (CVLT). Glomerular filtration rate was estimated in subjects with CKD using the six-variable Modification of Diet in Renal Disease equation. RESULTS: There was a graded relation between cognitive function and severity of CKD. Mean scores on the 3MS, Trails B, and CVLT immediate and delayed recall were significantly worse for subjects with ESRD than for subjects with CKD or published norms (P<.001 for all comparisons). Scores on the Trails B (P<.001) and CVLT immediate (P=.01) and delayed (P<.001) recall were significantly worse for subjects with CKD not requiring dialysis than for published norms. In addition, the fraction of subjects with impairment on the 3MS and Trails B increased with decreasing kidney function. CONCLUSION: Cognitive impairment is associated with the severity of kidney disease. Further studies are needed to determine the reasons for cognitive impairment in subjects with CKD and ESRD.

Physical and sexual function in women with chronic kidney disease.

BACKGROUND: Cross-sectional studies suggest an association between functional status and chronic kidney disease (CKD). Whether physical function deteriorates with progression of CKD is unknown. METHODS: To determine associations among CKD, physical function, and sexual function in women, we conducted cross-sectional and longitudinal analyses of 2,761 women enrolled in the Heart and Estrogen/Progestin Replacement Study. Physical and sexual function were evaluated using the Duke Activity Status Index (DASI) and the Sexual Problems Scale of the Medical Outcomes Study, respectively. Glomerular filtration rate (GFR) was estimated using the Modification of Diet in Renal Disease regression equation. In addition to analyses across the spectrum of GFR, CKD was categorized as mild (estimated GFR, 45 to 60 mL/min/1.73 m2), moderate (estimated GFR, 30 to 44 mL/min/1.73 m2), and severe (estimated GFR, <30 mL/min/1.73 m2) according to a modification of recently established classification guidelines. RESULTS: Mean age of study participants was 67 +/- 7 years, and mean estimated GFR was 61 +/- 14 mL/min/1.73 m2. In unadjusted analyses, mean baseline DASI score was 10 points lower in women with an estimated GFR less than 30 mL/min/1.73 m2 than in women with an estimated GFR of 60 mL/min/1.73 m2 or greater (P < 0.0001). Estimated GFR remained significantly associated with DASI score after multivariable adjustment. In longitudinal analyses, a decline in estimated GFR was associated with a significant decline in DASI score independent of baseline estimated GFR and other factors. There were no significant associations between estimated GFR and psychosocial aspects of sexual function. CONCLUSION: CKD is associated with impaired physical function, and a decline in estimated GFR is associated with a decline in physical function.

Analgesia in patients with ESRD: a review of available evidence.

Moderate to severe pain frequently accompanies chronic diseases in general and end-stage renal disease (ESRD) in particular. Several analgesic agents and associated metabolites show altered pharmacokinetics in the presence of reduced glomerular filtration rate. Drug-related side effects may exacerbate symptoms frequently observed in persons with chronic kidney disease (CKD; eg, fatigue, nausea, vomiting, and constipation) or those often attributed to hemodialysis therapy (eg, orthostatic hypotension and impaired cognition). Persons with advanced CKD and ESRD are at increased risk for adverse effects of analgesic agents because of enhanced drug sensitivity, comorbid conditions, and concurrent medication use. Dose adjustment and avoidance of certain analgesics may be required in patients with advanced CKD and ESRD. We review the available evidence on pharmacokinetics and adverse drug effects of various analgesic agents commonly used in patients with advanced CKD and ESRD. Determining an optimal approach to the control of pain in patients with advanced CKD and ESRD will require additional research.

Post transplant erythrocytosis in hypercalcemic renal transplant recipients.

In vitro data suggest that calcium plays an important role in normal and disordered erythropoiesis. The purpose of this study is to determine whether there is an association between serum calcium, various hormone levels, and the development of post transplant erythrocytosis (PTE). Data were collected on 283 patients who underwent renal transplantation between 1994 and 1998. The relationship between serum calcium and PTE development was tested using the chi-square test. Univariate and multivariable adjusted models were employed to determine predictors of maximum hematocrit. Selected patients underwent measurement of intact parathyroid hormone (PTH), 1,25-dihydroxy vitamin D, and erythropoietin (EPO). Seventy-three patients (26%) developed PTE. Post transplant erythrocytosis was more common in patients with hypercalcemia compared with patients with normal serum calcium (34% vs. 18%, p = 0.002). In multivariable analyses, serum calcium was a strong independent predictor of maximum hematocrit post transplant, even after adjustment for renal function. A serum calcium of >or=10.2 mg/dL was associated with greater than two-fold increased odds of PTE. There were no differences in hormone levels between subjects with hypercalcemia and PTE, subjects with PTE alone, and subjects with hypercalcemia alone. Hypercalcemia is associated with the development of PTE in renal transplant recipients.

Monitoring changes in gene expression in renal ischemia-reperfusion in the rat.

BACKGROUND: Although acute renal failure (ARF) is a relatively common disorder with major morbidity and mortality, its molecular basis remains incompletely defined. The present study examined global gene expression in the well-characterized ischemia-reperfusion model of ARF using DNA microarray technology. METHODS: Male Wistar rats underwent bilateral renal ischemia (30 min) or sham operation, followed by reperfusion for 1, 2, 3 or 4 days. Plasma creatinine increased approximately fivefold over baseline, peaking on day 1. Renal total RNA was used to probe cDNA microarrays. RESULTS: Alterations in expression of 18 genes were identified by microarray analysis. Nine genes were up-regulated (ADAM2, HO-1, UCP-2, and thymosin beta4 in the early phase and clusterin, vanin1, fibronectin, heat-responsive protein 12 and FK506 binding protein in the established phase), whereas another nine were down-regulated (glutamine synthetase, cytochrome p450 IId6, and cyp 2d9 in the early phase and cyp 4a14, Xist gene, PPARgamma, alpha-albumin, uromodulin, and ADH B2 in the established phase). The identities of these 18 genes were sequence-verified. Changes in gene expression of ADAM2, cyp2d6, fibronectin, HO-1 and PPARgamma were confirmed by quantitative real-time polymerase chain reaction (PCR). ADAM2, cyp2d6, and PPARgamma have not previously been known to be involved in ARF. CONCLUSION: Using DNA microarray technology, we identified changes in expression of 18 genes during renal ischemia-reperfusion injury in the rat. We confirmed changes in five genes (fibronectin, ADAM2, cyp 2d6, HO-1 and PPARgamma) by quantitative real-time PCR. Several genes, not previously been identified as playing a role in ischemic ARF, may have importance in this disease.

DNA microarray analysis of complex biologic processes.

DNA microarrays, or gene chips, allow surveys of gene expression, (i.e., mRNA expression) in a highly parallel and comprehensive manner. The pattern of gene expression produced, known as the expression profile, depicts the subset of gene transcripts expressed in a cell or tissue. At its most fundamental level, the expression profile can address qualitatively which genes are expressed in disease states. However, with the aid of bioinformatics tools such as cluster analysis, self-organizing maps, and principle component analysis, more sophisticated questions can be answered. Microarrays can be used to characterize the functions of novel genes, identify genes in a biologic pathway, analyze genetic variation, and identify therapeutic drug targets. Moreover, the expression profile can be used as a tissue or disease "fingerprint." This review details the fabrication of arrays, data management tools, and applications of microarrays to the field of renal research and the future of clinical practice.