Estimation of glomerular filtration rate in diabetic subjects: Cockcroft formula or modification of Diet in Renal Disease study equation?

OBJECTIVE: The Cockcroft-Gault formula is recommended for the evaluation of renal function in diabetic patients. The more recent Modification of Diet in Renal Disease (MDRD) study equation seems more accurate, but it has not been validated in diabetic patients. This study compares the two methods. RESEARCH DESIGN AND METHODS: In 160 diabetic patients, we compared the Cockcroft-Gault formula and MDRD equation estimations to glomerular filtration rates (GFRs) measured by an isotopic method ((51)Cr-EDTA) by correlation studies and a Bland-Altman procedure. Their accuracy for the diagnosis of moderately (GFR <60 ml . min(-1) . 1.73 m(-2)) or severely (GFR <30 ml . min(-1) . 1.73 m(-2)) impaired renal function were compared with receiver operating characteristic (ROC) curves. RESULTS: Both the Cockcroft-Gault formula (r = 0.74; P < 0.0001) and MDRD equation (r = 0.81; P < 0.0001) were well correlated with isotopic GFR. The Bland-Altman procedure revealed a bias for the MDRD equation, which was not the case for the Cockcroft-Gault formula. Analysis of ROC curves showed that the MDRD equation had a better maximal accuracy for the diagnosis of moderate (areas under the curve [AUCs] 0.868 for the Cockcroft-Gault formula and 0.927 for the MDRD equation; P = 0.012) and severe renal failure (AUC 0.883 for the Cockcroft-Gault formula and 0.962 for the MDRD equation; P = 0.0001). In the 87 patients with renal insufficiency, the MDRD equation estimation was better correlated with isotopic GFR (Cockcroft-Gault formula r = 0.57; the MDRD equation r = 0.78; P < 0.01), and it was not biased as evaluated by the Bland-Altman procedure. CONCLUSIONS: Although both equations have imperfections, the MDRD equation is more accurate for the diagnosis and stratification of renal failure in diabetic patients.     

Glucose control influences glomerular filtration rate and its prediction in diabetic subjects

OBJECTIVE: Hyperglycemia increases glomerular filtration rate (GFR), but the influence of HbA(1c) (A1C) on GFR and GFR's prediction by recommended equations remains to be determined. RESEARCH DESIGN AND METHODS: In 193 diabetic patients, we searched for an association between A1C and isotopically measured GFR (51Cr-EDTA) and their predictions by the Cockcroft and Gault formula (CG) and the modification of diet in renal disease (MDRD) equation. Their accuracy for the diagnosis of moderate (GFR <60 ml/min per 1.73 m(2)) or severe (GFR <30 ml/min per 1.73 m(2)) renal failure was compared from receiver operating characteristic (ROC) curves, before and after categorizing the patients as well (A1C 8%. The MDRD equation was more accurate and robust in diabetic patients with impaired renal function.     

How reliable is estimation of glomerular filtration rate at diagnosis of type 2 diabetes?

OBJECTIVE: The Cockcroft-Gault (CG) and Modification of Diet in Renal Disease (MDRD) equations previously have been recommended to estimate glomerular filtration rate (GFR). We compared both estimates with true GFR, measured by the isotopic (51)Cr-EDTA method, in newly diagnosed, treatment-na?ve subjects with type 2 diabetes. RESEARCH DESIGN AND METHODS: A total of 292 mainly normoalbuminuric (241 of 292) subjects were recruited. Subjects were classified as having mild renal impairment (group 1, GFR <90 ml/min per 1.73 m(2)) or normal renal function (group 2, GFR >/=90 ml/min per 1.73 m(2)). Estimated GFR (eGFR) was calculated by the CG and MDRD equations. Blood samples drawn at 44, 120, 180, and 240 min after administration of 1 MBq of (51)Cr-EDTA were used to measure isotopic GFR (iGFR). RESULTS: For subjects in group 1, mean (+/-SD) iGFR was 83.8 +/- 4.3 ml/min per 1.73 m(2). eGFR was 78.0 +/- 16.5 or 73.7 +/- 12.0 ml/min per 1.73 m(2) using CG and MDRD equations, respectively. Ninety-five percent CIs for method bias were -11.1 to -0.6 using CG and -14.4 to -7.0 using MDRD. Ninety-five percent limits of agreement (mean bias +/- 2 SD) were -37.2 to 25.6 and -33.1 to 11.7, respectively. In group 2, iGFR was 119.4 +/- 20.3 ml/min per 1.73 m(2). eGFR was 104.4 +/- 26.3 or 92.3 +/- 18.7 ml/min per 1.73 m(2) using CG and MDRD equations, respectively. Ninety-five percent CIs for method bias were -17.4 to -12.5 using CG and -29.1 to -25.1 using MDRD. Ninety-five percent limits of agreement were -54.4 to 24.4 and -59.5 to 5.3, respectively. CONCLUSIONS: In newly diagnosed type 2 diabetic patients, particularly those with a GFR >/=90 ml/min per 1.73 m(2), both CG and MDRD equations significantly underestimate iGFR. This highlights a limitation in the use of eGFR in the majority of diabetic subjects outside the setting of chronic kidney disease.     

Cystatin C and estimates of renal function: searching for a better measure of kidney function in diabetic patients

BACKGROUND: Early identification of impairment in renal function is crucial in diabetic patients. Serum cystatin C may be the most sensitive indicator of glomerular filtration rate (GFR) in the clinical setting. METHODS: We compared cystatin C with creatinine, the Cockcroft-Gault (C-G) formula, and the Modification of Diet in Renal Disease (MDRD) study equation for the assessment of early decreased renal function in 288 diabetic patients (125 type 1, 163 type 2) with renal impairment [GFR: 4-222 mL x min(-1) x (1.73 m(2))(-1)]. Relationships of cystatin C, creatinine, and iohexol clearance were linearized by plotting their reciprocals in a simple regression model. Diagnostic efficiency was calculated from ROC curves. RESULTS: In this study population, cystatin C (P = 0.0013) was better correlated with GFR (r = 0.857) than were creatinine (r = 0.772), C-G (r = 0.750), and MDRD (r = 0.806), a result replicated in patients with normal renal function (P = 0.023, type 1; P = 0.011, type 2), but not in those with decreased GFR. Mean cystatin C concentrations showed step-by-step statistically significant increases as GFR decreased, allowing very early detection of reduction in renal function. At 90 mL x min(-1) x (1.73 m(2))(-1) and 75 mL x min(-1) x (1.73 m(2))(-1) cut-points, diagnostic efficiencies of cystatin C (89% and 92%) were better than those of the other variables (79%-82% and 85%-86%, respectively; P = 0.01). CONCLUSIONS: All data supported the value of serum cystatin C compared with conventional estimates based on serum creatinine measurement for detecting very early reduction of renal function. Use of cystatin C to measure renal function will optimize early detection, prevention, and treatment strategies for diabetic nephropathy.     

Estimating glomerular filtration rate in black South Africans by use of the modification of diet in renal disease and Cockcroft-Gault equations

BACKGROUND: The 4-variable Modification of Diet in Renal Disease (4-v MDRD) and Cockcroft-Gault (CG) equations are commonly used for estimating glomerular filtration rate (GFR); however, neither of these equations has been validated in an indigenous African population. The aim of this study was to evaluate the performance of the 4-v MDRD and CG equations for estimating GFR in black South Africans against measured GFR and to assess the appropriateness for the local population of the ethnicity factor established for African Americans in the 4-v MDRD equation. METHODS: We enrolled 100 patients in the study. The plasma clearance of chromium-51-EDTA ((51)Cr-EDTA) was used to measure GFR, and serum creatinine was measured using an isotope dilution mass spectrometry (IDMS) traceable assay. We estimated GFR using both the reexpressed 4-v MDRD and CG equations and compared it to measured GFR using 4 modalities: correlation coefficient, weighted Deming regression analysis, percentage bias, and proportion of estimated GFR within 30% of measured GFR (P(30)). RESULTS: The Spearman correlation coefficient between measured and estimated GFR for both equations was similar (4-v MDRD R(2) = 0.80 and CG R(2) = 0.79). Using the 4-v MDRD equation with the ethnicity factor of 1.212 as established for African Americans resulted in a median positive bias of 13.1 (95% CI 5.5 to 18.3) mL/min/1.73 m(2). Without the ethnicity factor, median bias was 1.9 (95% CI -0.8 to 4.5) mL/min/1.73 m(2). CONCLUSIONS: The 4-v MDRD equation, without the ethnicity factor of 1.212, can be used for estimating GFR in black South Africans.     

Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation pronouncedly underestimates glomerular filtration rate in type 2 diabetes

OBJECTIVE To evaluate the performance of the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation to estimate glomerular filtration rate (GFR) in type 2 diabetic patients with GFR >60 mL/min/1.73 m(2). RESEARCH DESIGN AND METHODS This was a cross-sectional study including 105 type 2 diabetic patients. GFR was measured by (51)Cr-EDTA method and estimated by the MDRD and CKD-EPI equations. Serum creatinine was measured by the traceable Jaffe method. Bland-Altman plots were used. Bias, accuracy (P30), and precision were evaluated. RESULTS The mean age of patients was 57 ± 8 years; 53 (50%) were men and 90 (86%) were white. Forty-six (44%) patients had microalbuminuria, and 14 (13%) had macroalbuminuria. (51)Cr-EDTA GFR was 103 ± 23, CKD-EPI GFR was 83 ± 15, and MDRD-GFR was 78 ± 17 mL/min/1.73 m2 (P < 0.001). Accuracy (95% CI) was 67% (58-74) for CKD-EPI and 64% (56-75) for MDRD. Precision was 21 and 22, respectively. CONCLUSIONS The CKD-EPI and MDRD equations pronouncedly underestimated GFR in type 2 diabetic patients.     

Estimating glomerular filtration rate in HIV-infected adults in Africa: comparison of Cockcroft-Gault and Modification of Diet in Renal Disease formulae

BACKGROUND: Cockcroft-Gault (CG) and Modification of Diet in Renal Disease (MDRD) formulae are recommended for glomerular filtration rate (GFR) estimation, but neither has been validated or directly compared longitudinally in HIV-infected patients or in Africa. METHODS: We investigated differences between formulae in baseline GFR, GFR changes and incidence of impaired GFR after initiation of antiretroviral therapy (ART) in 3,316 HIV-infected adults in Africa, considering sex, age, body mass index and baseline laboratory parameters as predictors. RESULTS: Participants were 65% women, median age 36.8 years, median weight 56.7 kg. Baseline GFR was lower using CG (median 89 ml/min/1.73 m2, 7.4% <60 ml/min/1.73 m2) versus MDRD (103 ml/min/1.73 m2, 3.1% <60 ml/min/1.73 m2). At 36 weeks, median CG-GFR increased (92 ml/min/1.73 m2), whereas MDRD-GFR decreased (96 ml/min/1.73 m2). Weight (explicitly a factor in CG only) concurrently increased to 62.0 kg. GFR changes from weeks 36-96 (after weight stabilization) were similar across formulae. By 96 weeks, 56 patients developed severe GFR impairment (<30 ml/min/1.73 m2) using one or both formulae (both n=45, CG n=7, MDRD n=4) compared with only 24 by serum creatinine alone. Multivariate models identified different sets of predictors for each formula. CONCLUSIONS: Although severe GFR impairments are similarly classified by different formulae, moderate impairments were more frequently identified using CG-GFR versus MDRD-GFR (with Black ethnicity correction factor 1.21), and creatinine alone had low sensitivity. Given overestimation in underweight patients and sensitivity to weight changes, this MDRD formula might not necessarily be superior for monitoring ART in African HIV-infected adults.     

Assessing glomerular filtration rate in renal transplant recipients by estimates derived from serum measurements of creatinine and cystatin C

BACKGROUND: Assessing glomerular filtration rate (GFR) is of importance in the surveillance of renal transplant recipients. As serum markers alone are inaccurate for estimating GFR, several equations have been developed with the aim of translating a serum value into a corresponding and more accurate GFR. The present study investigated the diagnostic characteristics of GFR estimates obtained by the simplified MDRD formula and the cystatin C based estimate described by Larsson et al. METHODS: Prospective study in 29 stable renal transplant recipients. GFR was assessed with (125)I-Iothalamate clearance, creatinine was measured with a modified Jaffe method on Dimension RxL (Dade-Behring, Dudingen, Switzerland), cystatin C was determined by particle enhanced turbidimetric immunassay (PETIA; Dako, Glostrup, Denmark). Bias, precision and diagnostic accuracy of the two GFR estimates were assessed with Bland-Altman method and receiver-operating characteristics (ROC) analysis. The latter was performed at a GFR cut-off of 60 ml/min/1.73 m2. RESULTS: The cystatin C based GFR estimate normalized to a body surface area of 1.73 m2 exhibited a bias of -4.7 ml/min/1.73 m2, the 95% limits of agreement were -25.5-16 ml/min/1.73 m2 with an AUC of 0.87. The MDRD estimates obtained from the original creatinine revealed biased results. Thus, non-constant recalibration of creatinine was done. Recalibrated creatinine gave an MDRD GFR estimate with a bias of 1.7 ml/min/1.73 m2. The limits of agreement were -23.1-26.4 ml/min/1.73 m2. ROC analysis revealed an AUC 0.8 and was not significantly different from the cystatin C based GFR estimate. CONCLUSIONS: In renal transplant recipients, the cystatin C based GFR estimate exhibits similar diagnostic characteristics like the simplified MDRD formula. In contrast to cystatin C measurement, recalibration of creatinine might be necessary before implementing the simplified MDRD formula into clinical routine.     

肾小球滤过率评估方程在慢性肾小球肾炎患者中的应用评价

目的 评价Cockcroft-Gauh(CG)方程及肾脏疾病膳食改良试验(MDRD)方程计算的肾小球滤过率(GFR)在慢性肾小球肾炎患者的适用性.方法 选择2005年1月至2007年12月在中山大学附属第三医院肾内科就诊的慢性肾小球肾炎患者143例,用CG方程、MDRD1方程和简化MDRD方程,分别计算GFR值与99Tcm-DTPA检测的GFR(sGFR)进行比较.结果 Bland-Altman分析显示CG方程估计的GFR和sGFR的一致性较好,但所有各方程估计的GFR和sGFR的一致性限度均超过事先规定的专业界值.线性回归结果 显示,CG方程估测的GFR与x轴的斜率较其他方程更接近0.从总体以及慢性肾脏病(CKD)的不同分期分析,CG方程较其他方程有较小的偏差和更优的准确性.结论对于慢性肾小球肾炎患者肾功能的评估,当血肌酐的测定方法 为酶法时,CG方程优于MDRD1方程和简化MDRD方程.     

肾小球滤过率评估公式的准确性比较

目的评估Cockcroft-Gault(C-G)公式,简化MDRD公式对中国糖尿病患者肾功能估算的准确性。方法以99mTC-DTPA同位素测定的肾小球滤过率(GFR)为参考标准,分别用C-G公式和简化MDRD公式估算GFR(eGFR),与同位素测定结果进行比较,并进行一致性检验,评价估算公式的准确性。结果 (1)210例糖尿病患者(1型糖尿病12例,2型糖尿病198例),年龄(56.5±13.7)岁,体质量(68.1±10.9)kg,体质量指数(BMI)(24.6±3.4)kg/m2,血肌酐(76.9±34.3)μmol/L;(2)同位素测定GFR值为(85.2±25.0)ml·min-1·1.73m-2,C-G公式估算值为(97.0±37.2)ml·min-1·1.73m-2,简化MDRD公式估算值为(104.1±37.1)ml·min-1·1.73m-2;(3)C-G公式估算值与GFR的差值中位数为-6.47ml·min-1·1.73m-2,简化MDRD公式估算值与GFR的差值中位数为-16.5ml·min-1·1.73m-2;(4)相关性分析表明,实测GFR与年龄、病程、BMI、BUN、Cr、尿白蛋白比肌酐呈负相关;与身高、体质量、HbA1c无相关性;而CG公式估算的GFR与年龄,病程、BUN、Cr、尿白蛋白比肌酐呈负相关,与身高、体质量、HbA1c呈正相关,与BMI无相关性;MDRD公式估算的GFR与年龄、病程、BUN、Cr、尿白蛋白比肌酐呈负相关,与身高、HbA1c呈正相关,与体质量、BMI无相关性。(5)一致性检验分析表明,C-G公式Kappa值为0.554,MDRD公式Kappa值为0.646。结论与参考标准比较,两估算公式对于糖尿病患者肾功能的估算结果均不是非常理想;相比之下,MDRD公式的准确性优于C-G公式。     

Effect of low protein diet on the renal response to meat ingestion in diabetic nephropathy

We measured the renal haemodynamic and proteinuric response to a meat meal (MM) in ten persistently proteinuric insulin-dependent diabetic patients in a randomized cross-over study of 3 weeks on low protein diet (LPD) or normal protein intake (NPD). On LPD, protein intake (0.64 +/- 0.05 vs 1.15 +/- 0.09 g kg-1 body weight (BW) per day, P less than 0.001), plasma urea (6.6 +/- 1.3 vs 11.0 +/- 2.0 mmol l-1, P less than 0.01) and urea appearance (0.06 +/- 0.01 vs 0.16 +/- 0.03 gN kg-1 body weight per day, P less than 0.001) were lower. Baseline glomerular filtration rate (GFR), renal plasma flow (RPF) and renal vascular resistance (RVR) were similar on the two diets and there were no significant average changes in these variables after the meat meal on either diet (NPD, before vs after MM: GFR: 67 +/- 11 vs 71 +/- 13 ml min-1 1.73 m-2; RPF: 479 +/- 70 vs 512 +/- 81 ml min-1 1.73 m-2; RVR: 181 +/- 45 vs 179 +/- 52 mmHg min-1 l-1); (LPD, before vs after MM: GFR: 64 +/- 10 vs 67 +/- 11 ml min-1 1.73 m-2; RPF: 506 +/- 60 vs 533 + 52 ml min-1 1.73 m-2; RVR: 151 +/- 28 vs 146 +/- 32 mmHg min-1 l-1). However, all patients with baseline GFR above 60 ml min-1 1.73 m-2 showed a GFR rise in response to the meat meal on both diets, while patients with lower baseline values tended to reduce their GRF.(ABSTRACT TRUNCATED AT 250 WORDS)     

肾小球滤过率评估方程在慢性肾脏病患者中的应用评价

目的:评价11种常用的肾小球滤过率(GFR)评估方程在慢性肾脏病(CKD)患者中的适用性.方法: 选择119例CKD患者,用Coekcroft-Gault(CG)方程、MDRD1方程、MDRD3方程、简化MDRD方程、Jelliffe1973(JE73)方程、Mawer(MA)方程、Hull(HU)方程、Jellife1971(JE71)方程、血肌酐倒数公式、Gate(GA)方程、Bjornsson(BJ)方程,分别预测GFR值,与99mTc DTPA测的GFR(sGFR)进行比较.结果:上述11种方程预测的GFR值和sGFR值比较显示,CG方程、MDRD1方程、JE73方程、MA方程、HU方程、JE71方程、GA方程、BJ方程预测的GFR值和sGFR值的差异没有统计学意义.将患者按CKD的不同分期分组,用配对t检验,分别比较上述8种方程预测的GFB值和sGFR值的差异,结果显示只有JE73方程在CKD各期中预测的GFR值和8GFR值的差异均没有统计学差异.结论:JE73方程可能更适合我国CKD患者.     

Glomerular filtration rate, urinary albumin excretion rate, and blood pressure changes in normoalbuminuric normotensive type 1 diabetic patients: an 8-year follow-up study.

OBJECTIVE: To analyze the changes in glomerular filtration rate (GFR), urinary albumin excretion rate (UAER), and blood pressure (BP) levels in a cohort of normoalbuminuric and normotensive type 1 diabetic patients. RESEARCH DESIGN AND METHODS: This is an 8.4+/-2.1-year prospective study of 33 normotensive normoalbuminuric (24-h UAER <20 microg/min) type 1 diabetic patients. UAER (radioimmunoassay), GFR (51Cr-EDTA single-injection technique), and GHb (ion-exchange chromatography) were measured at baseline and at 1- to 2-year intervals. RESULTS: The GFR decreased (137.6+/-16.5 to 116.4+/-21.3 ml x min(-1) x 1.73 m(-2) P < 0.05) during the follow-up period. GFR reduction (-0.20+/-0.29 ml x min(-1) x month(-1); P < 0.05) was associated with baseline GFR and mean GHb (R2 = 0.30; beta = 0.072; F = 6.54; P = 0.004). UAER was higher at the end of the study (3.7-7.1 microg/min; P = 0.017). Microalbuminuria was observed in two patients, while macroalbuminuria was observed in one. No changes in UAER were observed when these three patients were excluded from the analysis. Mean blood pressure (MBP) increased during the study (85.8+/-9.7 to 99.6+/-11.6 mmHg; P < 0.001). MBP at the end of the study was associated with age and GFR at baseline (R2 = 0.39; beta = 0.074; F = 9.64; P = 0.001). CONCLUSIONS: In this cohort of normoalbuminuric normotensive type 1 diabetic patients, GFR decreased and BP levels increased during the follow-up period. The predictors for the GFR change were baseline GFR level and metabolic control. For end-of-study MBP, the predictor was baseline GFR level.     

Long-term renoprotective effect of nisoldipine and lisinopril in type 1 diabetic patients with diabetic nephropathy

OBJECTIVE: To compare the long-term effect on kidney function of a long-acting calcium antagonist (nisoldipine) versus a long-acting ACE inhibitor (lisinopril) in hypertensive type 1 diabetic patients with diabetic nephropathy. RESEARCH DESIGN AND METHODS: We performed a 4-year prospective, randomized, double-dummy controlled study comparing nisoldipine (20-40 mg once a day) with lisinopril (10-20 mg once a day). The study was double-blinded for the first year and single-blinded thereafter. The study included 51 hypertensive type 1 diabetic patients with diabetic nephropathy. Three patients dropped out during the first month; results for the remaining 48 patients are presented. RESULTS: At baseline, the two groups were comparable: glomerular filtration rate (GFR) was 85 +/- 5 and 85 +/- 6 ml x min(-1) x [1.73 m](-2); mean 24-h ambulatory blood pressure was 108 +/- 3 and 105 +/- 2 mmHg, and albuminuria was 1,554 mg/24 h (95% CI 980-2,465) and 1,033 mg/24 h (760-1,406) in the lisinopril and nisoldipine groups, respectively. Mean 24-h arterial blood pressure during the study did not differ between the lisinopril and nisoldipine groups (100 +/- 2 and 103 +/- 1 mmHg, respectively). The time-course of albuminuria differed between groups (P < 0.001). Whereas initiation of treatment with lisinopril resulted in a reduction from baseline albuminuria by 52% (95% CI 14-73), albuminuria in the nisoldipine group did not change throughout the study GFR declined in a biphasic manner with an initial (0-6 months) reduction of 1.3 +/- 0.3 ml x min(-1) x month(-1) in the lisinopril group compared with 0.2 +/- 0.4 ml x min(-1) x month(-1) in the nisoldipine group (P < 0.01). The subsequent sustained decline (6 to 48 months or the end of treatment) was identical in the two groups: 0.5 +/- 0.1 ml min(-1) x month(-1) (NS). Two patients in the lisinopril group and three patients in the nisoldipine group entered therapy for end-stage renal failure. CONCLUSIONS: Long-term treatment with lisinopril or nisoldipine has similar beneficial effects on progression of diabetic nephropathy in hypertensive type 1 diabetic patients.     

Lower hemoglobin concentrations and subsequent decline in kidney function in an apparently healthy population aged 60 year and older

BACKGROUND: Anemia and decreased kidney function are recognized as risk factors for morbidity and mortality in the elderly. The role of hemoglobin in renal function changes among elderly patients is not fully understood. METHODS: Of 1,500 people screened, 121 normotensive non-diabetic elderly patients were recruited, and underwent biochemistry examinations at the baseline, second and fourth years of a 4-year longitudinal study. Serum creatinine and calculated renal parameters, including the Cockroft-Gault (CG) formula, Modification of Diet in Renal Disease (MDRD) Study and abbreviated MDRD (abMDRD) equations were used to evaluate renal function and progression of kidney disease. Chronic kidney disease (CKD) was defined as a glomerular filtration rate (GFR) of <60 ml/min/1.73 m(2). Multivariate regression analyses were used to explore predictors for decline in renal parameters. RESULTS: Ages ranged from 60 to 81 year (mean: 71.8+/-3.8). Baseline hemoglobin concentrations ranged from 11.9 to 17.3 g/dl (mean: 14.1+/-1.1). Serum creatinine increased and CG creatinine clearance (CrCl), MDRD and abMDRD GFR decreased during follow-up (all p< or =0.001). The prevalence of CKD significantly increased only in those with baseline hemoglobin concentrations of <14 g/dl (p< or =0.03, based on findings of both MDRD and abMDRD GFR). Baseline hemoglobin correlates with 4-year changes of MDRD and abMDRD GFR in univariate (both p<0.001) and multivariate regression analyses (both p<0.05). CONCLUSIONS: This longitudinal study revealed that the aging process was associated with decline of renal function in the elderly. Because hemoglobin concentrations are an independent predictor for subsequent decline in kidney function, it should be considered in the assessment of renal disease and GFR in the elderly.     

Comparison of the modification of diet in renal disease and Cockcroft-Gault equations for antimicrobial dosage adjustments

BACKGROUND: Direct measurement of glomerular filtration rate (GFR) is considered to be the most accurate method of assessing kidney function, albeit difficult and costly. With the derivation of the Modification of Diet in Renal Disease (MDRD) equation to estimate GFR in patients with chronic kidney disease, questions exist as to whether this method should be preferred over the Cockcroft-Gault (CG) equation when making dosage adjustments for renally eliminated antimicrobials. OBJECTIVE: To determine whether a difference exists when making antimicrobial dosage adjustments in patients with chronic kidney disease based on estimation of GFR using the MDRD and CG equations. METHODS: We conducted an observational analysis of 409 patients with chronic kidney disease who were admitted to a tertiary care facility with an inpatient dialysis center and nephrology unit. GFR was calculated using both the 4- or 6-variable MDRD equation and the CG equation and compared using correlation and Bland-Altman methodology. Dosage discordance rates of the selected antimicrobials were determined on the basis of manufacturer renal dose recommendations. RESULTS: Average +/- SD GFR for all patients using the CG equation was 34.8 +/- 12 mL/min and, using the MDRD equation, was 40.2 +/- 12 mL/min (absolute mean difference 5.40; 95% CI 4.66 to 6.15; p < 0.001). The correlation coefficient between the 2 estimations, among all patients, was excellent (r = 0.80). The Bland-Altman plot yielded limits of agreement of -9.8 and 20.6; thus, the MDRD estimation may range from 9.8 mL/min below to 20.6 mL/min above the CG estimation for 95% of the cases. A discordance rate of 21-37% (p < 0.001) existed among the recommended dosing adjustments of the selected antimicrobials. CONCLUSIONS: This analysis demonstrated statistically significant differences between the CG and MDRD equations, resulting in different dosing recommendations in 21-37% of patients. The clinical significance of these differences is uncertain in the absence of data regarding clinical outcomes that would result from the use of the discordant doses.     

Accurate estimation of glomerular filtration rate in diabetic nephropathy from age, body weight, and serum creatinine.

OBJECTIVE--To assess, in diabetic nephropathy, the accuracy of a method that estimates glomerular function with age, body weight, and serum creatinine as parameters. RESEARCH DESIGN AND METHODS--Glomerular filtration rate (GFR) was measured 57 times in 20 subjects with insulin-dependent diabetes mellitus and nephropathy with a single injection of 51Cr-EDTA. At the same time, the estimated creatinine clearance (ml/min) was calculated with the Cockroft-Gault formula (140 - age [yr]) x body wt [kg] x K/serum creatinine [mumol/L]) K = 1.23 for men, 1.05 for women These values were then corrected for body surface area (1.73 m2). RESULTS--For GFR measurements less than 100 ml.min-1.1.73 m-2 (n = 41), there was a strong positive correlation with the estimated creatinine clearance corrected for body surface area (r = 0.94, P less than 0.0001). The slope of this regression line did not differ significantly from identity or the y-intercept from zero. On average, the Cockroft-Gault formula (corrected for body surface area) underestimated the GFR by only 3.1 ml.min-1.1.73 m-2 (9.7 SD). CONCLUSIONS--This formula, corrected for body surface area, gives accurate estimates of GFR when GFR less than 100 ml.min-1.1.73 m-2. This formula could be used with an acceptable degree of confidence when repeated isotope assessments of renal function in diabetic nephropathy are impracticable.     

肾小球滤过率评估方程在慢性肾脏病患者中的应用评价

目的 评价11种常用的肾小球滤过率(GFR)评估方程在慢性肾脏病(CKD)患者的适用性。方法 选择119例CKD患者，用Cockcroft-Gault（CG）方程、MDRD1方程、MDRD3方程、简化MDRD方程、Jelliffe1973（JE73）方程、Mawer（MA）方程、Hull（HU）方程、Jellife1971（JE71）方程、血肌酐倒数公式、Gate（GA）方程、Bjornsson（BJ）方程，分别预测GFR值，与99mTc DTPA测的GFR（sGFR）进行比较。结果 上述11种方程预测的GFR值和sGFR值比较显示，CG方程、MDRD1方程、JE73方程、MA方程、HU方程、JE71方程、GA方程、BJ方程预测的GFR值和sGFR值的差异没有统计学意义。将患者按CKD的不同分期分组，用配对t检验，分别比较上述8种方程预测的GFR值和sGFR值的差异，结果显示只有JE73方程在CKD各期中，预测的GFR值和sGFR值的差异均没有统计学差异。结论 Jelliffe1973方程可能更适合我国CKD患者。     

PC-1 amino acid variant Q121 is associated with a lower glomerular filtration rate in type 2 diabetic patients with abnormal albumin excretion rates

OBJECTIVE: To study the relationships between the PC-1 K121Q variant and diabetic nephropathy (DN) in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: A total of 125 patients with type 2 diabetes and abnormal albumin excretion rate (AER) (range 20-5416 microg/min) were followed up for 4 years with repeated measurements of glomerular filtration rate (GFR). Genomic DNA was extracted from all patients, and the PC-1 K121Q polymorphism was determined by the PCR AvaII restriction enzyme. A subset of 64 patients underwent a percutaneous kidney biopsy at baseline, and glomerular structure was analyzed by electron microscopic morphometric analysis. At baseline, age (56 +/- 8 vs. 59 +/- 7 years), BMI (28.3 +/- 4.3 vs. 28.6 +/- 3.7 kg/m(2)), known duration of type 2 diabetes (11.1 +/- 7 vs. 11.9 +/- 8 years), and HbA(1c) (8.6 +/- 1.8 vs. 8.4 +/- 1.7%) were similar in K121K (KK, n = 87, 73 men/14 women) and XQ (35 K121Q + 3 Q121Q, n = 38, 27 men/11 women) patients. Baseline GFR was 96 +/- 28 ml. min(-1). 1.73 m(-2) and was related (P = 0.01-0.001) to age, known diabetes duration, and systolic blood pressure. RESULTS: XQ patients had lower GFR (P < 0.05) than KK patients (88 +/- 30 vs. 100 +/- 26 ml. min(-1). 1.73 m(-2)); this difference persisted also after factoring in age and known diabetes duration. The rate of progression of DN was similar in KK and XQ patients: %deltaGFR was 4.1/year (median, range: 22.9-30.6) vs. 4.2/year (9.8-26.7). Morphometric parameters of diabetic glomerulopathy were similar in the two genotype groups. CONCLUSIONS: Among patients with type 2 diabetes with abnormal AER, those carrying the Q PC-1 genotype have more severe DN but not a faster GFR decline than KK patients, thus suggesting faster DN development since diabetes diagnosis in XQ patients.     

Effect of a chicken-based diet on renal function and lipid profile in patients with type 2 diabetes: a randomized crossover trial

OBJECTIVE: To assess the effect of replacing red meat with chicken in the usual diet and the effect of a low-protein diet on glomerular filtration rate (GFR), urinary albumin excretion rate (UAER), and lipid levels in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: A randomized, crossover, controlled trial was conducted with 28 patients with type 2 diabetes (seven women; mean age 58.1 years): 15 patients were normoalbuminuric (UAER <20 microg/min), and 13 patients were microalbuminuric (UAER 20-200 microg/min). A chicken-based diet (red meat replaced with chicken) and a low-protein diet were compared with the patients' usual diet. Patients followed each diet for 4 weeks with a 4-week washout period between. GFR ((51)Cr-EDTA single-injection technique), 24-h UAER (immunoturbidimetry), apolipoprotein B, total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides were measured after each diet. RESULTS: Normoalbuminuric and microalbuminuric patients with diabetes were analyzed separately. In normoalbuminuric patients, GFR after the chicken (101.3 +/- 22.9 ml x min(-1) x 1.73 m(-2)) and low-protein diets (93.8 +/- 20.5 ml x min(-1) x m(-2)) was lower than after the usual diet (113.4 +/- 31.4 ml x min(-1) x 1.73 m(-2); P < 0.05). In microalbuminuric patients, apolipoprotein B levels were lower after the chicken (113.5 +/- 36.0 mg/dl) and low-protein diets (103.5 +/- 40.1 mg/dl) than after the usual diet (134.3 +/- 30.7 mg/dl; P < 0.05). Only the chicken diet reduced UAER (median 34.3 microg/min) compared with the low-protein (median 52.3 microg/min) and usual (median 63.8 microg/min) diets (P < 0.05). Glycemic control and blood pressure did not change after the diets. CONCLUSIONS: A normoproteic diet with chicken as the only source of meat may represent an alternative strategy for treatment of patients with type 2 diabetes and microalbuminuria.