Longitudinal analysis of performance of estimated glomerular filtration rate as renal function declines in chronic kidney disease

Background. Numerous studies have assessed the accuracy of equationsestimating glomerular filtration rate (eGFR) from serum creatininein individuals with chronic kidney disease (CKD) in cross-sectionalstudies. Limited literature exists, however, on the consistencyof performance of these equations in longitudinal studies asrenal function declines. Methods. Radionucleotide-measured GFR from 155 predialysis patientswith stage 3–5 CKD was compared with eGFR derived fromfour equations [6-variable Modification of Diet in Renal Disease(6-MDRD), 4-variable MDRD (4-MDRD), Cockcroft–Gault (CG)and Cockcroft–Gault equations corrected for body surfacearea (CGC)] at baseline, 12 and 24 months. Bias (differencebetween eGFR and measured GFR) was used as a measure of performance.Restricted Maximum Likelihood (REML) models were used to identifyvariables potentially affecting the performance of estimatingequations across time. Results. Mean measured GFR (±SD) at baseline, 12 and24 months was 25.9 ± 10.7, 23.1 ± 10.6 and 20.3± 10.1 mL/min/1.73 m², respectively. There was a statisticallysignificant negative association between bias and GFR for allfour estimates (range: –0.76 to –0.71, P < 0.001for all), indicating worsening underestimation and overestimationat higher and lower GFR, respectively. This negative associationsignificantly reduced over the 24 months (P < 0.001); however,this was largely due to persistent underestimation of eGFR fromindividuals with GFR >50 mL/min/1.73 m². For those with abaseline GFR <50 mL/min/1.73 m², the change in bias for anyof the four equations over 24 months was 1.1 mL/min/1.73 m²,suggesting relatively preserved performance with time. The MDRDequations showed a sustained advantage in estimating renal functionthat was more evident as GFR declined. Conclusion. GFR estimates are inexpensive and show an acceptablelongitudinal performance for monitoring CKD patients with GFR<50 mL/min/1.73 m². Inaccuracies appear more substantialabove this level of GFR, and care with interpretation is required.     

Mortality risk stratification in chronic kidney disease: one size for all ages?

Current National Kidney Foundation Kidney Disease Outcomes Quality Initiative staging criteria for chronic kidney disease (CKD) are intended to apply to all age groups. However, it is unclear whether different levels of estimated GFR (eGFR) have the same prognostic significance in older and younger patients. The study cohort was composed of Department of Veterans Affairs (VA) patients who were aged 18 to 100 yr and had at least one outpatient serum creatinine measurement between October 1, 2001, and September 30, 2002 (n=2583,911). Patients with ESRD were excluded. GFR was estimated using the Modification of Diet in Renal Disease equation using each patient's first outpatient creatinine measurement during the study period. The association of eGFR with survival was measured by age group. Twenty percent of cohort patients had an eGFR<60 ml/min per 1.73 m2, ranging from 3% among 18- to 44-yr-olds to as high as 49% among 85- to 100-yr-olds. Fifty-two percent (n=266,421) of cohort patients with an eGFR<60 ml/min per 1.73 m2 had "very" moderate reductions in eGFR into the 50- to 59-ml/min per 1.73 m2 range. The association of eGFR with mortality was weaker in the elderly than in younger age groups: Whereas severe reductions in eGFR were associated with an increased risk for death in all age groups, "very" moderate reductions in eGFR (50 to 59 ml/min per 1.73 m2) were associated with an increased adjusted risk for death only among patients who were younger than 65 yr. Age-related attenuation of the association of eGFR with mortality was also present among women and black patients. In the clinical setting, mortality risk stratification in elderly patients should not be based on the same eGFR cut points as for younger age groups and would benefit from finer categorization of the 30- to 59-ml/min per 1.73 m2 eGFR group.     

Association of chronic kidney disease with outcomes in chronic heart failure: a propensity-matched study

Background. Chronic kidney disease (CKD) is associated withincreased mortality in patients with heart failure (HF). However,its association with hospitalization in HF patients has notbeen well studied. Methods. Of 7788 patients in the Digitalis Investigation Grouptrial, 3527 had CKD, defined by an estimated glomerular filtrationrate (GFR) <60 ml/min/1.73 m² body surface area (BSA). Propensityscores for CKD were calculated using a multivariable logisticregression model and used to match 2399 pairs of patients withand without CKD. Matched Cox regression analyses were used toestimate association of CKD with outcomes. Results. All-cause hospitalization occurred in 1636 (rate, 4233/10 000person-years) and 1587 (rate, 3733/10 000 person-years)patients respectively, with and without CKD (matched hazardratio [HR] for CKD, 1.18, 95% confidence interval [CI], 1.08–1.29;P < 0.0001). Matched HR for cardiovascular and HF hospitalizationwere respectively 1.17 (95% CI, 1.06–1.28, P = 0.002)and 1.28 (95% CI, 1.13–1.45, P < 0.0001). Comparedto GFR 60 ml/min/1.73 m² BSA, HR for all-cause hospitalizationfor GFR 45–59 and <45 ml/min/1.73 m² BSA were respectively1.04 (95% CI, 0.94–1.16; P = 0.422) and 1.58 (95% CI,1.34–1.87; P < 0.0001). Similarly, HR for all-causedeath for GFR 45–59 and <45 ml/min/1.73 m² BSA wererespectively 1.03 (95% CI, 0.90–1.18; P = 0.651) and 1.70(95% CI, 1.40–2.07; P < 0.0001). Matched HR for deathdue to cardiovascular causes and progressive HF were respectively1.24 (95% CI, 1.09–1.40; P = 0.001) and 1.42 (95% CI,1.16–1.72; P = 0.001). Conclusion. CKD was associated with increased mortality andhospitalization in ambulatory patients with chronic HF, whichincreased progressively with worsening kidney function.     

Off-pump versus on-pump coronary artery bypass grafting outcomes stratified by preoperative renal function

Clinical trials of off-pump coronary artery bypass grafting (CABG) have largely excluded patients with CKD. Here, we sought to determine whether pump status affects outcomes in patients with CKD. Using a nonrandomized cohort of 742,909 non-emergent, isolated CABG cases, which included 158,561 off-pump cases, in the Society of Thoracic Surgery Database from 2004 through 2009, we evaluated the association between pump status (off-pump versus on-pump) and in-hospital death or incident renal replacement therapy (RRT) across strata of preoperative renal function. We used propensity methods to adjust patient- and center-level analyses for imbalances in baseline patient risk. Patients who received on-pump and off-pump CABG had similar mean age and distribution of preoperative estimated GFR (eGFR). In a propensity-weighted analysis, off-pump CABG was associated with a reduction in the composite in-hospital death or RRT, with patients having lower preoperative renal function exhibiting greater benefit, on average. The risk difference (on-pump minus off-pump) ranged from 0.05 (95% confidence interval, -0.06 to 0.16) per 100 patients for eGFR ≥ 90 ml/min per 1.73 m(2) to 3.66 (95% confidence interval, 2.14-5.18) per 100 patients for eGFR 15-29 ml/min per 1.73 m(2). Both component endpoints suggested the same trend. In summary, these data suggest that patients with CKD experience less death or incident RRT when treated with off-pump compared with on-pump CABG. The reduction in incident RRT, not death, drove this effect on the composite among patients with low eGFR. Prospective trials comparing these procedures in patients with impaired preoperative renal function are warranted.     

Are prediction equations for glomerular filtration rate useful for the long-term monitoring of type 2 diabetic patients?

Background. The aim of this study was to compare the accuracyof prediction equations [modification of diet in renal disease(MDRD), simplified MDRD, Cockcroft–Gault (CG), reciprocalof creatinine and creatinine clearance] in a cohort of patientswith type 2 diabetes. Methods. A total of 525 glomerular filtration rates (GFRs) using¹²⁵I-iothalamate were carried out over 10 years in 87 type 2diabetic patients. Accuracy was evaluated at three levels ofrenal function according to the baseline values obtained withthe isotopic method: hyperfiltration (GFR: >140 ml/min/1.73m²; 140 isotopic determinations in 27 patients), normal renalfunction (GFR: 140–90 ml/min/1.73 m²; 294 isotopic determinationsin 47 patients) and chronic kidney disease (CKD) stages 2–3(GFR: 30–89 ml/min/1.73 m²; 87 isotopic determinationsin 13 patients). The annual slope for GFR (change in GFR expressedas ml/min/year) was considered to ascertain the variabilityin the equations compared with the isotopic method during follow-up.Student's t-test was used to determine the existence of significantdifferences between prediction equations and the isotopic method(P < 0.05 with Bonferroni adjusted for five contrast tests). Results. In the subgroup of patients with hyperfiltration, aGFR slope calculated with ¹²⁵I-iothalamate –4.8 ±4.7 ml/min/year was obtained. GFR slope in patients with normalrenal function was –3.0 ± 2.3 ml/min/year. In bothsituations, all equations presented a significant underestimationcompared with the isotopic GFR (P < 0.01; P < 0.05). Inthe subgroup of CKD stages 2–3, the slope for GFR with¹²⁵I-iothalamate was –1.4 ± 1.8 ml/min/year. Thebest prediction equation compared with the isotopic method provedto be MDRD with a slope for GFR of –1.4 ± 1.3 ml/min/year(P: NS) compared with the CG formula –1.0 ± 0.9ml/min/year (P: NS). Creatinine clearance presented the greatestvariability in estimation (P < 0.001). Conclusions. In the normal renal function and hyperfiltrationgroups, none of the prediction equations demonstrated acceptableaccuracy owing to excessive underestimation of renal function.In CKD stages 2–3, with mean serum creatinine 133 µmol/l(1.5 mg/dl), the MDRD equation can be used to estimate GFR duringthe monitoring and follow-up of patients with type 2 diabetesreceiving insulin, anti-diabetic drugs or both.     

Elevated relative mortality risk with mild-to-moderate chronic kidney disease decreases with age.

BACKGROUND: Renal disease is common in the general population and whilst few people progress to end-stage renal failure, mortality is increased. The aim of this study was to examine all-cause mortality risk in relation to chronic kidney disease (CKD) stages defined by estimated glomerular filtration rate (eGFR). METHODS: Data were extracted from a computerized central laboratory system for a defined geographical area over a 3-year study period. The eGFR was calculated using the four-variable Modification of Diet in Renal Disease (MDRD) formula and aligned to the MDRD laboratory. Average annual mortality and relative risk (RR) of all-cause mortality was determined and compared for defined age and CKD bands. RESULTS: 106 366 participants (55.5% female; 85% White, 13% South Asian, 2% Black and others) were eligible and studied, representing 49% of the Coventry adult population. 12 540 (12%) of the sample had some evidence of decreased kidney function, with an eGFR <60 ml/min/1.73 m2. 7611 (7%) participants died and there were significantly elevated risks of mortality with increasing renal dysfunction; RR = 4.0, 8.3, 16.2 and 43.5 for eGFR 45-59, 30-44, 15-29 and <15 ml/min/1.73 m2, respectively. Within age bands, RRs were statistically significantly raised with CKD progression and within CKD stage, RR of death decreased as age increased. CONCLUSIONS: CKD prevalence increased with age and absolute and RR of mortality increased with progression of CKD. People aged over 75 years, with mild-to-moderate renal disease, representing 41% of this age group, have no increased RR of mortality. Further study of CKD and mortality, particularly progression over time and with respect to age is needed.     

Implication of CKD-EPI Equation to Estimate Glomerular Filtration Rate in Chinese Patients with Chronic Kidney Disease

Abstract

Objective: To evaluate the applicability of the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation to estimate glomerular filtration rate (GFR) in Chinese patients of different stages of CKD. Methods: The CKD-EPI equation estimated GFR (eGFR) was compared with body surface area standardized GFR (sGFR), which was measured by diethylenetriaminepentaacetic acid renal dynamic imaging method in 142 CKD cases. Results: eGFR was positively correlated with sGFR (r = 0.838, p < 0.001). eGFR of 15%, 30%, and 50% accuracy were 31.0%, 57.7%, and 76.8%, respectively. Average deviation of eGFR from sGFR was ?0.92 ± 16.36 mL/min/1.73 m² (p = 0.506). There was no significant deviation in the CKD from stages 2 to 5. However, in CKD stage 1, the deviation was increased with the value of 13.36 ± 18.44 mL/min/1.73 m² (p = 0.023). Conclusion: CKD-EPI equation might be widely used in evaluation of Chinese CKD patients of different stages, with a less deviation and higher accuracy. However, in CKD stage 1, eGFR was higher than sGFR on average. It was suggested that eGFR might be overcorrected or overestimated. These results demonstrated that careful modification of CKD-EPI equation would be necessary in Chinese populations with CKD.     

Estimated or Measured GFR in Living Kidney Donors Work‐up?

The value of estimated glomerular filtration rate (eGFR) in living kidney donors screening is unclear. A recently published web‐based application derived from large cohorts, but not living donors, calculates the probability of a measured GFR (mGFR) lower than a determined threshold. Our objectives were to validate the clinical utility of this tool in a cohort of living donors and to test two other strategies based on chronic kidney disease epidemiology collaboration (CKD‐EPI) and on MDRD‐eGFR. GFR was measured using ⁵¹Cr‐ ethylene‐diamine tetraacetic acid urinary clearance in 311 potential living kidney donors (178 women, mean age 50 ± 11.6 years). The web‐based tool was used to predict those with mGFR < 80 mL/min/1.73 m². Inputs to the application were sex, age, ethnicity, and plasma creatinine. In our cohort, a web‐based probability of mGFR <90 mL/min/1.73 m² higher than 2% had 100% sensitivity for detection of actual mGFR <80 mL/min/1.73 m². The positive predictive value was 0.19. A CKD‐EPI‐eGFR threshold of 104 mL/min/1.73 m² and an MDRD‐eGFR threshold of 100 mL/min/1.73 m² had 100% sensitivity to detect donors with actual mGFR <80 mL/min/1.73 m². We obtained similar results in an external cohort of 354 living donors. We confirm the usefulness of the web‐based application to identify potential donors who should benefit from GFR measurement.     

Trends in the timing of pre-emptive kidney transplantation

Pre-emptive kidney transplantation is considered the best available renal replacement therapy, but no guidelines exist to direct its timing during CKD progression. We used a national cohort of 19,471 first-time pre-emptive kidney transplant recipients between 1995-2009 to evaluate patterns and implications of transplant timing. Mean estimated GFR (eGFR) at the time of pre-emptive transplant increased significantly over time, from 9.2 ml/min/1.73 m(2) in 1995 to 13.8 ml/min/1.73 m(2) in 2009 (P<0.001). Patients with eGFR ≥ 15 ml/min/1.73 m(2) represented an increasing proportion of pre-emptive transplant recipients, from 9% in 1995 to 35% in 2009; the trend for patients with eGFR ≥ 10 was similar (30% to 72%). We did not detect statistically significant differences in patient survival or death-censored graft survival between strata of eGFR at the time of transplant, either in the full cohort or in subgroup analyses of patients who might theoretically benefit from earlier pre-emptive transplantation. In summary, pre-emptive kidney transplantation is occurring at increasing levels of native kidney function. Earlier transplantation does not appear to associate with patient or graft survival, suggesting that earlier pre-emptive transplantation may subject donors and recipients to premature operative risk and waste the native kidney function of recipients.     

Age as a determinant of glomerular filtration rate in non-insulin-dependent diabetes mellitus

BACKGROUND: The level of glomerular filtration rate (GFR) and its determinantsin non-insulin-dependent diabetes mellitus (NIDDM) are currentlycontroversial. DESIGN OF THE STUDY: We measured GFR and effective renal plasma flow (ERPF) in 121consecutive NIDDM without evidence of overt diabetic nephropathy.Age varied from 28 to 70 years, 61.2% were women and known durationof NIDDM was 0–37 years. Hypertension was detected in36.4% of patients and 47.8% had microalbuminuria. RESULTS: An inverse correlation was found between GFR and age, but notwith known duration of NIDDM. It was a weak correlation (r=–0.41)but statistically significant (P<0.001). The other variablesconsidered were not significant by multiple stepwise regressionanalysis, but patients with lower GFR tended to have diabeticretinopathy more frequently. GFR was lower in hypertensive comparedto normo tensive patients (123±28.4 versus 136±32.5ml/min/1.73 m²; P<0.05), but was not different between patientswith normal and elevated albumin excretion rate. ERPF also hadan inverse correlation with age (r=–0.45, P<0.001). CONCLUSION: We conclude that (i) age should be considered as a confoundingvariable when evaluating GFR in patients with NIDDM, and (ii)the age-dependent decline in GFR may mask hyperfiltration inthe early stages of diabetic nephropathy in NIDDM.     

内蒙古呼伦贝尔地区成人慢性肾脏病流行病学调查

目的 探讨我国内蒙古自治区呼伦贝尔少数民族聚居区成年人群中慢性肾脏病（CKD）患病率及其危险因素。 方法 对该地区20岁以上常住居民进行CKD抽样调查,被调查者均检测了尿白蛋白/肌酐比率、血尿（离心后尿沉渣显微镜检查）及估计肾小球滤过率（eGFR,检验血清肌酐后用国人校正的简化MDRD公式计算）;并同时调查了CKD的相关危险因素。 结果 符合入选条件的被调查者共4522例,白蛋白尿阳性率为7.11%;血尿阳性率为2.64%;eGFR低于60 ml&#8226;min-1&#8226;(1.73 m2)-1者为2.75%;去除白蛋白尿、血尿及eGFR下降共同存在造成的重复,该地区CKD患病率为12.95%。高血压患病率38.90%,糖代谢异常6.61%,脂代谢异常34.60%,腰围增大24.79%,代谢综合征15.02%。多因素Logistic回归分析及分层分析显示,年龄增加、腰围增大、收缩压升高、空腹血糖升高、血清三酰甘油增高及患代谢综合征与白蛋白尿发生相关;年龄增加、收缩压升高及空腹血糖升高与肾功能下降相关;年龄增加与血尿发生相关。 结论 内蒙古自治区呼伦贝尔地区CKD患病率为12.95%。相关危险因素包括年龄增加、腰围增大、高血压、血糖或血脂异常、及代谢综合征。     

Is the Chronic Kidney Disease Epidemiology Collaboration four‐level race equation better than the cystatin C equation?

Aim: To evaluate the Chronic Kidney Disease Epidemiology Collaboration (CKD‐EPI) four‐level race equation in the assessment of glomerular filtration rate (GFR) in Chinese people with chronic kidney disease (CKD), which was published in 2011, compared with the cystatin C‐based GFR estimation equation (CysC GFR) and the combination of CysC and serum creatinine equation (CysC‐Scr GFR). Methods: The CKD‐EPI four‐level race equation estimated GFR (CKD‐EPI GFR) was compared with the CysC GFR and CysC‐Scr GFR. Three equations were compared with body surface area (BSA) standardized GFR (sGFR), which was measured by ^99mTc‐DTPA renal dynamic imaging method in 111 CKD cases. Results: A statistically significant correlation was found between sGFR and CKD‐EPI GFR, CysC GFR and CysC‐Scr GFR. Three estimated GFR (eGFR) equations of 30% accuracy were 58.6%, 56.8% and 63.5%, respectively. Average deviations of eGFR from sGFR were 2.34, 1.19, and 1.32 (mL/min per 1.73 m²) (P > 0.05), respectively. There was no significant deviation in the CKD from stages 1 to 5 in CKD‐EPI GFR and CysC‐Scr GFR. However, when estimated by CysC GFR, the deviation was increased, with the value of 12.41 mL/min per 1.73 m² (P= 0.002) in CKD stage 5. Conclusion: Our results showed that in a Chinese population with CKD, CKD‐EPI GFR, CysC GFR and CysC‐Scr GFR of bias and overall accuracy of 30% were very similar. There was little advantage in adding Asian coefficient to modifying the CKD‐EPI equation. CysC GFR overestimated GFR in patients with CKD stages 4 and 5.     

Prevalence of chronic kidney disease in Kinshasa: results of a pilot study from the Democratic Republic of Congo

Background. The burden of chronic kidney disease (CKD) in sub-SaharanAfrica is unknown. The aim of this study was to investigatethe prevalence and the risk factors associated with CKD in Kinshasa,the capital of the Democratic Republic of Congo (DRC). Methods. In a cross-sectional study, 503 adult residents in10 of the 35 health zones of Kinshasa were studied in a randomlyselected sample. Glomerular filtration rate was estimated usingthe simplified Modification of Diet in Renal Disease Study equation(eGFR) and compared with the Cockcroft–Gault equationfor creatinine clearance. The associations between health characteristics,indicators of kidney damage (proteinuria) and kidney function(<60 ml/min/1.73 m²) were examined. Results. The prevalence of all stages of CKD according to K/DOQIguidelines was 12.4% [95% confidence interval (CI), 11.0–15.1%].By stage, 2% had stage 1 (proteinuria with normal eGFR), 2.4%had stage 2 (proteinuria with an eGFR of 60–89 ml/min/1.73m²), 7.8% had stage 3 (eGFR, 30–59 ml/min/1.73 m²) and0.2% had stage 5 (eGFR < 15 ml/min/1.73 m²). Hypertensionand age were independently associated with CKD stage 3. Theprevalences of major non-communicable diseases considered inthis study were 27.6% (95% CI, 25.7–31.3%) for hypertension,11.7% (95% CI, 10.3–14.4%) for diabetes mellitus and 14.9%(95% CI, 13.3–17.9%) for obesity. Hypertension was alsoindependently associated with proteinuria. Conclusion. More than 10% of the Kinshasa population exhibitssigns of CKD, which is affecting adults in their productiveyears. Risk factors for CKD, including hypertension, diabetesand obesity, are increasing. These alarming data must guidecurrent and future healthcare policies to meet the challengeraised by CKD in this city and hopefully in the whole country.     

Age affects outcomes in chronic kidney disease

Chronic kidney disease (CKD) is common among the elderly. However, little is known about how the clinical implications of CKD vary with age. We examined the age-specific incidence of death, treated end-stage renal disease (ESRD), and change in estimated glomerular filtration rate (eGFR) among 209,622 US veterans with CKD stages 3 to 5 followed for a mean of 3.2 years. Patients aged 75 years or older at baseline comprised 47% of the overall cohort and accounted for 28% of the 9227 cases of ESRD that occurred during follow-up. Among patients of all ages, rates of both death and ESRD were inversely related to eGFR at baseline. However, among those with comparable levels of eGFR, older patients had higher rates of death and lower rates of ESRD than younger patients. Consequently, the level of eGFR below which the risk of ESRD exceeded the risk of death varied by age, ranging from 45 ml/min per 1.73 m(2) for 18 to 44 year old patients to 15 ml/min per 1.73 m(2) for 65 to 84 year old patients. Among those 85 years or older, the risk of death always exceeded the risk of ESRD in this cohort. Among patients with eGFR levels <45 ml/min per 1.73 m(2) at baseline, older patients were less likely than their younger counterparts to experience an annual decline in eGFR of >3 ml/min per 1.73 m(2). In conclusion, age is a major effect modifier among patients with an eGFR of <60 ml/min per 1.73 m(2), challenging us to move beyond a uniform stage-based approach to managing CKD.     

Decline in kidney function before and after nephrology referral and the effect on survival in moderate to advanced chronic kidney disease.

BACKGROUND: The burden of chronic kidney disease (CKD) is high, but its natural history and the benefit of routine nephrology care is unclear. This study investigated the decline in kidney function prior to and following nephrology referral and its association with mortality. METHODS: This study provides a retrospective review of the individual rates of glomerular filtration rate (GFR) decline (millilitre per minute per 1.73 m(2)/year) for the 5 years before and after referral in 726 new referrals with stages 3-5 CKD to one renal unit between 1997 and 2003. Blood pressures are averages at referral, 1 and 3 years post referral. Logistic regression and Cox's models tested factors predicting post-referral GFR decline and the impact on mortality. RESULTS: Mean (SD) age was 72 (14), and 389 (54%) patients had stages 4-5 CKD. GFR decline slowed significantly from -5.4 ml/min/1.73 m(2)/year (-13. to -2) before to -0.35 ml/min/1.73 m(2)/year (-3 to +3) after referral (P < 0.001). Blood pressure also reduced significantly (155/84 to 149/80, P < 0.05) with most changes occurring within 1 year of referral. Factors predicting a non-progressive post-referral decline included a lower systolic blood pressure at referral and 1 year after referral, a CKD diagnosis other than diabetic nephropathy, less baseline proteinuria and a non-progressive pre-referral GFR decline. A non-progressive post-referral GFR decline was independently associated with significantly better survival (hazard ratio 0.55, 95% CI 0.40-0.75, P 相似文献   

Kidney function can improve in patients with hypertensive CKD

The typical assumption is that patients with CKD will have progressive nephropathy. Methodological issues, such as measurement error and regression to the mean, have made it difficult to document whether kidney function might improve in some patients. Here, we used data from 12 years of follow-up in the African American Study of Kidney Disease and Hypertension to determine whether some patients with CKD can experience a sustained improvement in GFR. We calculated estimated GFR (eGFR) based on serum creatinine measurements during both the trial and cohort phases. We defined clearly improved patients as those with positive eGFR slopes that we could not explain by random measurement variation under Bayesian mixed-effects models. Of 949 patients with at least three follow-up eGFR measurements, 31 (3.3%) demonstrated clearly positive eGFR slopes. The mean slope among these patients was +1.06 (0.12) ml/min per 1.73 m(2) per yr, compared with -2.45 (0.07) ml/min per 1.73 m(2) per yr among the remaining patients. During the trial phase, 24 (77%) of these 31 patients also had clearly positive slopes of (125)I-iothalamate-measured GFR during the trial phase. Low levels of proteinuria at baseline and randomization to the lower BP goal (mean arterial pressure ≤92 mmHg) associated with improved eGFR. In conclusion, the extended follow-up from this study provides strong evidence that kidney function can improve in some patients with hypertensive CKD.     

Prevalence of chronic kidney disease based on estimated glomerular filtration rate and proteinuria in Icelandic adults.

BACKGROUND: The purpose of this study was to compare three different equations to calculate estimated glomerular filtration rate (eGFR) based on serum creatinine (SCr) and to estimate the prevalence of chronic kidney disease (CKD) in the Icelandic population. METHODS: This was a cross-sectional study using data from the Reykjavik Heart Study. GFR was estimated with three equations: Equation I was based on 1/SCr; Equation II based on the Cockcroft-Gault equation; and Equation III was the modified MDRD equation. The eGFR calculated with Equation III and proteinuria were used to estimate the prevalence of CKD. The prevalence was age-standardized to the truncated world population. We used chi-square and ANCOVA to compare the group with low eGFR to age-matched controls. RESULTS: The subjects consisted of 9229 males and 10,027 females, aged 33-85 years. The equations performed very differently. Equation I showed women with higher eGFR than men and little change with age. Equation II showed men with higher eGFR than women and marked decline in eGFR with age. Equation III was similar to Equation II but the decline in eGFR with age was not as great. Regardless of the equation used, most subjects (63.7-80.7%) had an eGFR in the range of 60-89 ml/min/1.73 m2. Using Equation III, age-standardized prevalence of low eGFR for the population aged 35-80+ years was estimated to be 4.7 and 11.6% for men and women, respectively. The proportion of subjects with eGFR <60 ml/min/1.73 m2 increased with advancing age. An additional 2.39% of men and 0.89% of women had proteinuria. The prevalence of renal and cardiovascular risk factors including proteinuria, hypertension, lipid abnormalities and markers of inflammation was higher among those with low eGFR than age-matched controls. CONCLUSIONS: GFR estimates and the prevalence of CKD are dependent on the equation used to calculate eGFR. Unexpectedly, a low proportion of the Icelandic population had normal kidney function according to the eGFR regardless of the equation used. These equations may not be useful in epidemiological research.     

Chronic kidney disease in renal transplant recipients

The aim of the present study was to investigate the utility in renal transplant patients of the guidelines for the diagnosis and classification of chronic kidney disease (CKD) based on the estimated glomerular filtration rate (GFR) elaborated by the Kidney Disease Outcomes Quality Initiative (K/DOQI) of the National Kidney Foundation. PATIENTS AND METHODS: Four hundred forty-seven cadaveric kidney transplants performed between 1980 and 1994 with graft function at 12 months were included in the study. The GFR was calculated according to the MDRD equation. RESULTS: The mean GFR at 12 months was 54.5 +/- 20.3 mL/min/1.73 m(2): 23 patients (5.1%) had a GFR > or =90 mL/min/1.73 m(2); 136 patients (30.6%), 60-89; 246 (54.7%), 30-59; 35 patients (7.8%), 15-29; and 7 patients (1.6%), GFR <15. Similar distribution of CKD stages was observed at 5 and 10 years. Unadjusted graft survival at 10 years was better among patients with a higher GFR at 12 months: 87% in patients with GFR >90 mL/min/1.73 m(2); 83% of GFR 60-89 mL/min/1.73 m(2); 63%, GFR 30-59 mL/min/1.73 m(2); and 23%, GFR <30 mL/min/1.73 m(2) (P < .001). The association between GFR and graft survival persisted when adjusted by the age and gender of the recipients and donors, time on dialysis, body mass index, immunosuppression, delayed graft function, rejection, and HLA mismatches. The prevalence of complications, such as anemia, hypertension, dyslipidemias, and number of drugs increased as GFR declined. CONCLUSIONS: More than 60% of recipients presented chronic kidney disease. GFR was a predictive factor for graft survival at 10 years. The classification of renal transplant patients by CKD stages may help to identify patients with increased risk of graft loss and also to design strategies to improve outcomes.     

Inaccuracies in estimated glomerular filtration rate in one Australian renal centre

Background: Early identification of true renal disease (glomerular filtration rate (GFR) < 60 mL/min) results in better patient outcomes. There is now routine reporting in Australia of estimated GFR (eGFR) in all patients over age 18 who have serum creatinine measured, calculated by the Modification of Diet in Renal Disease (MDRD) formula, which was validated in an American Caucasian cohort. Significant clinical decisions and prognosis are often made on the basis of this calculation. Aim: To assess the accuracy of three estimates of GFR in an Australian population by comparing eGFR obtained by the abbreviated MDRD (aMDRD), Cockcroft–Gault corrected for body surface area (BSA) (CG) and Chronic Kidney Disease Epidemiology (CKD‐Epi) formulae with a gold standard, isotopic ⁵¹Cr‐ethylenediaminetetra‐acetic acid (⁵¹Cr‐EDTA) GFR. Methods: Patients referred with an eGFR of <60 mL/min reported by the aMDRD formula underwent isotopic measurement of GFR (over 4 h) and had eGFR calculated using CG corrected for BSA, aMDRD and CKD‐Epi formulae. Data were analysed using Bland–Altman plots and regression analysis to compare methods; bias, precision and the proportion of patients correctly stratified by stage of chronic kidney disease (CKD) were also compared according to the three estimates of GFR, using ⁵¹Cr‐EDTA GFR as the gold standard. Results: A total of 139 patients were recruited (female 45%), mean age 64 years and mean serum creatinine 212 µmol/L. The mean GFR (SD) (mL/min per m²) for isotopic, CG, aMDRD and CKD‐Epi were 47 (28), 37 (20), 32 (17) and 33 (18) (P = 0.001). CG (57%) was more likely to correctly stage CKD than aMDRD (37%) or CKD‐Epi (37%), and absolute bias was significantly lower using CG than either other method (P = 0.001). Conclusion: In this small Australian population the CG formula corrected for BSA agreed more closely with isotopic GFR and correctly staged patients with CKD more often than the aMDRD or CKD‐Epi formulae. It is important that each renal Unit considers the accuracy of estimates of GFR according to their population demographics.     

Moderate chronic kidney disease and cognitive function in adults 20 to 59 years of age: Third National Health and Nutrition Examination Survey (NHANES III)

Previous studies among elderly suggest an association between chronic kidney disease (CKD) and cognitive impairment. The purpose of this study was to determine whether moderate CKD is associated with cognitive performance among young, healthy, ethnically diverse adults. Three computerized cognitive function tests of visual-motor reaction time (Simple Reaction Time), visual attention (Symbol Digit Substitution), and learning/concentration (Serial Digit Learning) were administered to a random sample of participants, aged 20 to 59 yr, who completed initial interviews and medical examination in the Third National Health and Nutrition Examination Survey (NHANES III). Participants for this study (n = 4849) completed at least one cognitive function test. GFR was estimated using the Modification of Diet in Renal Disease (MDRD) equation. Moderate CKD was defined as estimated GFR (eGFR) 30 to 59 ml/min per 1.73 m(2). Unadjusted, residual-adjusted, and multivariate-adjusted logistic regression models were used. The cohort was 49.0% male and 11.6% black, and median (interquartile range) age was 36 yr (27 to 45) and eGFR was 107.9 ml/min per 1.73 m(2) (95.0 to 125.4). There were 31 (0.8%) prevalent cases of moderate CKD. Models were adjusted for residual effects of age, gender, race, diabetes, and other known potential confounders. In multivariate models, moderate CKD was not significantly associated with reaction time but was significantly associated with poorer learning/concentration (odds ratio 2.41; 95% confidence interval 1.30 to 5.63) and impairment in visual attention (odds ratio 2.74; 95% confidence interval 1.01 to 7.40). In summary, among those in a large nationally representative sample of healthy, ethnically diverse 20- to 59-yr-old adults, moderate CKD, reflected by eGFR 30 to 59 ml/min per 1.73 m(2), was significantly associated with poorer performance in visual attention and learning/concentration.