Estimating glomerular filtration rate in hypertensive subjects: Comparison of the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and Modification of Diet in Renal Disease (MDRD) Study equations

Abstract

Background.The Modification of Diet in Renal Disease (MDRD) Study equation is the most commonly used formula for estimation of glomerular filtration rate (eGFR). Recently, the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) developed a new equation to provide a more accurate estimate of GFR among individuals with normal or mildly reduced renal function.

Aim. To compare the MDRD and CKD-EPI equations in hypertensive population treated in general practice.

Methods. The MDRD and CKD-EPI equations were applied to a cohort of 994 hypertensive subjects aged 45–70 years without cardiovascular or renal disease or previously known diabetes.

Results. The prevalence of CKD stage 3 (eGFR 30–59 mL/min per 1.73 m²) was 6.7% (95% CI 5.3–8.5) (67/994) according to the MDRD formula and 3.7% (95% CI 2.6–5.1) (37/994) according to the CKD-EPI formula. Of the 67 subjects classified as having CKD stage 3 according to the MDRD equation, 30 (44.8%) were reclassified as ‘no-CKD’ by the CKD-EPI equation. These subjects were mostly women 26/30 (87.7%).

Conclusion. Using the CKD-EPI equation leads to lower prevalence estimates for CKD than the MDRD equation in a hypertensive population treated in general practice.     

A Foot Ergometer for Graded Muscular Exercise

Objective: In 2002, a uniform definition of chronic kidney disease (CKD) became widely accepted. The level of glomerular filtration rate (GFR) is the pivot for staging the disease. Because GFR is not readily measured in routine clinical practice, statistical models such as the Modification of Diet in Renal Disease (MDRD) equation have been proposed for estimating GFR. The MDRD equation is gaining worldwide acceptance in assisting the diagnosis and staging of CKD. Material and methods: We use theoretical and experimental considerations based on serum creatinine (Scr) measurements obtained with an enzymatic IDMS-traceable assay and compare CKD classifications based on Scr alone with classifications based on the eGFR-MDRD and eGFR-Mayo Clinic equations. Results: Based on recently published reference intervals for enzymatically determined Scr, we show that eGFR-MDRD<60 mL/min/1.73m² corresponds extremely well with Scr>upper reference limit. The different CKD stages III, IV and V can be redefined using Scr alone, resulting in 97.5% agreement. Conclusion: We show that neither the MDRD study equation nor the Mayo Clinic equation add extra value to the information already contained in Scr itself. Because of the limited applicability of the eGFR equations, Scr has even more potential to assist in the diagnosis and classification of CKD than eGFR-MDRD.     

Reference intervals for serum creatinine with enzymatic assay and evaluation of four equations to estimate glomerular filtration rate in a healthy Chinese adult population

BackgroundWith the wide usage of enzymatic assays to determine serum creatinine (Scr) in China, reference interval (RI) needs to be established. At the same time, the performance of Scr based equations to calculate estimated glomerular filtration rate (eGFR) in healthy Chinese adults has not been extensively investigated.MethodsThis study has strictly followed the International Federation of Clinical Chemistry (IFCC) recommendations and the Clinical Laboratory Standards Institute (CLSI) C28-A2 document. A total number of 778 healthy Chinese adults (male 433, female 345) were enrolled in this study.ResultsBy nonparametric method, RIs for males were: < 60 years, 58–93 μmol/l and > 60 years, 54–109 μmol/l; RIs for females were: < 60 years, 42–69 μmol/l and > 60 years, 43–83 μmol/l. Modification of Diet in Renal Disease (MDRD) equation and MDRD for Japanese made the percentage of eGFR > 90 ml/min/1.73 m² 31.7% and 4.9%; percentage of eGFR 60–89 ml/min/1.73 m² 65.2% and 64.0%, respectively. Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation and CKD-EPI for Asian made the percentage of eGFR > 90 ml/min/1.73 m² 89.2% and 94.0%; percentage of eGFR 60–89 ml/min/1.73 m² 10.3% and 5.7%, respectively.ConclusionScr RIs of healthy Chinese adults were found to be lower than those of Caucasians. Two MDRD equations underestimated GFR, while two CKD-EPI equations seemed to estimate a reasonable distribution of eGFR in healthy Chinese adult populations.     

Estimating glomerular filtration rate (GFR) in diabetes: The performance of MDRD and CKD-EPI equations in patients with various degrees of albuminuria

Objectives

The aim of this study was to compare the performance of Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and Modification of Diet in Renal Disease Study (MDRD) equations in estimating GFR in a large cohort of diabetic patients with various degrees of albuminuria.

Design and methods

In a group of 842 diabetic patients GFR was estimated from standardized creatinine, with MDRD-Study and CKD-EPI equations, and their performance evaluated regarding clinical stages of albuminuria and chronic kidney disease (CKD).

Results

Patients with normoalbuminuria had higher eGFR when calculated by CKD-EPI, than MDRD-Study equation [median (IQR): 103 (91–115) vs 97 (85–113) mL/min/1.73 m², P = 0.006, n = 364], which significantly influenced the prevalence of stage 1 CKD [eGFR > 90 mL/min/1.73 m²: 76.7% (CKD-EPI) vs. 65.1% (MDRD-Study), P = 0.005]. There were no differences between the eGFR values derived by two equations in patients with micro- and macroalbuminuria, and more advanced staging of CKD.

Conclusion

CKD-EPI equation might be a superior surrogate marker of GFR in patients with normoalbuminuria and hyperfiltration and could be used as a screening tool for early renal impairment in diabetes. It's validity as a marker of progression of diabetic nephropathy merits further investigation.     

Comparison of modification of diet in renal disease and chronic kidney disease epidemiology collaboration formulas in predicting long-term outcomes in patients undergoing stent implantation due to stable coronary artery disease

Introduction

The aim was to assess the predictive value of estimated glomerular filtration rate (eGFR) using two formulas: modification of diet in renal disease (MDRD) and chronic kidney disease epidemiology collaboration (CKD-EPI), in a population with stable coronary artery disease (SCAD) undergoing percutaneous coronary revascularization (PCI).

Methods

The analyzed cohort included 3,141 consecutive patients with SCAD who underwent PCI, between January 2006 and December 2011. Follow-up data were available for 3,123 (99.4 %) patients.

Results

The median follow-up was 1,127 days (interquartile range 566–1,634 days). During the observation period, 330 deaths were reported. In patients with serum creatinine (S-Cr) within normal range, eGFR by CKD-EPI equation predicted long-term outcome more accurately, than eGFR by MDRD formula—continuous Net Reclassification Improvement: 0.296 (95 % CI, 0.08–0.5 p = 0.03). In patients with elevated S-CR, eGFR calculated by both formulae had similar efficacy in assessing death risk. After adjustment for differences in clinical characteristics, both formulae were associated with mortality, but only in patients with elevated S-Cr: eGFR by MDRD (per 10 ml/min/1.73 m²) HR: 0.74 [95 % CI, 0.61–0.89, p = 0.002], eGFR by CKD-EPI (per 10 ml/min/1.73 m²) HR: 0.75 (95 % CI, 0.63–0.89, p = 0.001). After adjustment for covariates, eGFR by CKD-EPI equation did not offer more appropriate categorization of individuals with respect to long-term mortality.

Conclusion

Our results indicate that in multivariable analysis eGFR calculated by MDRD and CKD-EPI equations has similar predictive value. In a population of patients with SCAD and S-Cr within normal range, eGFR calculated by CKD-EPI equation outperforms eGFR calculated by MDRD equation in assessing death risk.     

Revised equations for estimating glomerular filtration rate based on the Lund-Malmö Study cohort

Abstract

Objective. To increase the accuracy of estimated GFR (eGFR) from creatinine overall and at measured GFR ≥90 mL/min per 1.73 m² by revising the Lund-Malmö (LM) equations, to elaborate on more complex forms to improve the LM and CKD-EPI equations further, and to assess benefits of adding lean body mass (LBM). Material and methods. Swedish Caucasians (n = 850, 376 women; median 60, range 18–95 years) referred for GFR measurement (plasma iohexol-clearance: median 55, range 5–173 mL/min/1.73 m²) constituted the Lund-Malmö Study cohort. Bias, precision, accuracy, expressed as median absolute percentage difference and percentage of estimates ±10% (P₁₀) and ±30% (P₃₀) of measured GFR, and classification ability with respect to five GFR stages were compared with the original LM, CKD-EPI and MDRD equations. Results. LM Revised overall performed better than LM Original without LBM due to increased accuracy at measured GFR ≥90 mL/min/1.73 m². Further extensions of the CKD-EPI or LM equations did not substantially improve overall performance. In particular, the performance of LM Revised at measured GFR ≥90 mL/min/1.73 m² could not be improved further without decreasing accuracy and classification ability at lower GFR-levels. Adding LBM to the equations had no strong effect on accuracy. Conclusion. Comparisons with the CKD-EPI and MDRD equations suggest that the LM equations are superior for the present Swedish population, due to markedly higher accuracy of the LM equations at measured GFR <30 mL/min/1.73 m². However, the LM equations cannot be recommended for use in general clinical practice until validated in other populations.     

Call for the use of a common equation for glomerular filtration rate estimation in East and South-East Asia

BackgroundEstimated glomerular filtration rate (eGFR) is currently calculated using various equations and serum creatinine (Scr) value measured by different assays. Differences among these eGFRs deserve further study.MethodsVolunteers from eight Asian regions (n = 3283; age 20–65 years, 1454 men, 1829 women) were recruited. The Chronic Kidney Disease Epidemiology Collaboration equation (EPI), Modification of Diet in Renal Disease Study equation (MDRD) for Japanese (MDRD_Jap) and MDRD for Chinese (MDRD_Chi) were selected. Jaffe and enzymatic assays were used to measure Scr. Six eGFRs were obtained for each volunteer: EPI equation using Scr value of enzymatic assay (EPI/E) and Jaffe assay (EPI/J); MDRD_Jap equation using Scr value of the two assays (MDRD_Jap/E, MDRD_Jap/J); and MDRD_Chi equation using Scr value of the two assays (MDRD_Chi/E, MDRD_Chi/J).ResultsNeither Scr nor eGFR showed significant regional difference. We compared eGFR calculated using the same equation but with different assays. The medians (2.5%, 97.5%) of eGFR difference were 2.0 (− 7, 14) mL/min/1.73 m² for EPI, 3.0 (− 12.0, 18.0) mL/min/1.73 m² for MDRD_Jap, and 5.0 (− 18, 30) mL/min/1.73 m² for MDRD_Chi. We also compared eGFR calculated using different equations but with the same assay. The medians (2.5%, 97.5%) of eGFR difference were 11 (− 6, 56) mL/min/1.73 m² between MDRD_Chi/E and EPI/E; 26 (9, 35) mL/min/1.73 m² between EPI/E and MDRD_Jap/E; and 39 (22, 65) mL/min/1.73 m² between MDRD_Chi/E and MDRD_Jap/E, respectively.ConclusionseGFR difference caused by using different equations is much larger than that caused by using different Scr assays. A common equation for GFR estimation is encouraged for use in Asians.     

Evaluation of creatinine, cystatin C and eGFR by different equations in professional cyclists during the Giro d'Italia 3-weeks stage race

Abstract In this study, creatinine-based equations to evaluate glomerular filtration rate (eGFR) were proposed to more accurately assess kidney function, and cystatin C, a parameter not dependent on muscular mass, was introduced to improve GFR calculation in professional cyclists during a long-lasting race. Nine cyclists participating in the 2011 Giro d'Italia were recruited. Blood and anthropometrical data were collected the day before (T-1) the race, on the 12th day (T 12) and on the 22nd day (T 22) of the race. Haemoglobin and haematocrit were registered. Haemodilution was observed at T 12, whilst stabilization was evident at T 22. Creatinine, cystatin C concentrations and eGFR values were not modified during the observed period; only GFR evaluated with the Cockcroft-Gault (CG) formula and expressed as ml/min/1.73 m(2) significantly decreased (p < 0.05) at T 22 in comparison with T-1, probably as a consequence of weight decrease. Cystatin C levels were in the reference range, while creatinine concentrations were lower. The lowest eGFR values were observed with CG normalized and the Modification of Diet in Renal Disease (MDRD) formulas. A good correlation was observed between the MDRD and the Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) equations and between CG normalized and both CKD-EPI and MDRD formulas. The worst correlation was registered between CKD-EPI creatinine and cystatin C and all the other equations. In conclusion, adaptive mechanisms of renal function allow athletes to maintain stable creatinine, cystatin C and eGFR values during a long-lasting race. The use of GFR equations to evaluate general health status of sportsmen should be recommended with caution, considering also weight modification during competition.     

Evaluation of creatinine,cystatin C and eGFR by different equations in professional cyclists during the Giro d'Italia 3-weeks stage race

Abstract

In this study, creatinine-based equations to evaluate glomerular filtration rate (eGFR) were proposed to more accurately assess kidney function, and cystatin C, a parameter not dependent on muscular mass, was introduced to improve GFR calculation in professional cyclists during a long-lasting race. Nine cyclists participating in the 2011 Giro d'Italia were recruited. Blood and anthropometrical data were collected the day before (T ? 1) the race, on the 12th day (T 12) and on the 22nd day (T 22) of the race. Haemoglobin and haematocrit were registered. Haemodilution was observed at T 12, whilst stabilization was evident at T 22. Creatinine, cystatin C concentrations and eGFR values were not modified during the observed period; only GFR evaluated with the Cockcroft-Gault (CG) formula and expressed as ml/min/1.73 m² significantly decreased (p < 0.05) at T 22 in comparison with T ? 1, probably as a consequence of weight decrease. Cystatin C levels were in the reference range, while creatinine concentrations were lower. The lowest eGFR values were observed with CG normalized and the Modification of Diet in Renal Disease (MDRD) formulas. A good correlation was observed between the MDRD and the Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) equations and between CG normalized and both CKD-EPI and MDRD formulas. The worst correlation was registered between CKD-EPI creatinine and cystatin C and all the other equations. In conclusion, adaptive mechanisms of renal function allow athletes to maintain stable creatinine, cystatin C and eGFR values during a long-lasting race. The use of GFR equations to evaluate general health status of sportsmen should be recommended with caution, considering also weight modification during competition.     

6种基于血肌酐的肾小球滤过率估算公式在健康人群中的应用评估

目的评价基于酶法和苦味酸速率法的血清肌酐的6种估算的肾小球滤过率（eGFR）公式在表观健康人群中的适用性。方法从健康体检人群中筛选出694名表观健康人,分别用酶学方法和碱性苦味酸速率法检测血清肌酐,通过6种eGFR公式[Cockcroft—Gault（C—G）公式、简化肾脏病膳食改善（MDRD）公式、MDRD-中国人公式、同位素稀释质谱法（IDMS）-MDRD公式、慢性肾脏病流行病合作组（CKD-EPI）公式和EPI-亚洲人（EPI-Asian）公式]分别计算其eGFR并进行比较。结果694名表观健康人群的血肌酐检测结果分别为酶法（65．8±13．3）μmolfL（范围为36～117μmol／L）,苦味酸速率法（83．0±12．7）μmol／L（范围为57～131μmol／L）。以eGFR值男性85—125mL／min、女性75—115mL／min作为参考区间,基于酶法检测肌酐的eGFR值在表观健康人群中的适用性依次为CKD—EPI公式（72．3％）〉IDMS—MDRD公式（69．9％）〉简化MDRD公式（61．3％）〉EPI—Asian公式（60．7％）〉C—G公式（54．8％）〉MDRD一中国人公式（27．3％）（P〈0．05）,IDMS—MDRD公式在男、女性之间的适用性差异最小（仅相差1．6％）;基于苦味酸速率法检测肌酐的eGFR值在表观健康人群中的适用性依次为MDRD一中国人公式（80．0％）〉EPI—Asian公式（70．1％）〉CKD—EPI公式（63．8％％）〉简化MDRD公式（59．1％）〉C—G公式（52．4％）〉IDMS—MDRD公式（40．7％）（P〈0．05）,MDRD-中国人公式在男、女性之间的适用性差异最小（仅相差1％）。结论以上6种eGFR公式计算结果有明显差异。如果用溯源至IDMS的酶法检测血清肌酐,可选用CKD—EPI公式、IDMS—MDRD公式来评价中国北方健康人群的eGFR;如果用苦味酸速率法检测血清肌酐,可选用MDRD-中国人公式来评价中国北方健康人群的eGFR。     

苦味酸法和酶法检测肌酐对肾小球滤过率预测公式效能的影响

目的 探讨应用苦味酸法和酶法检测肌酐对GFR评估方程适用性的影响.方法 选取2007-2009年华北(北京)、东北(大连)、华东(上海)、华中(长沙)4个区域三级甲等综合医院CKD患者176例.以双血浆法99m Tc-二乙三胺五乙酸(99mTc-DTPA)血浆清除率作为176例CKD患者的rGFR.使用4个不同厂家的酶法或苦味酸法肌酐试剂配套不同厂家自动生化分析仪分别测定患者血肌酐,同时应用体表面积( BSA)标化的Cockcroft-Gault方程(CG/BSA方程)、简化MDRD方程、校正至同位素稀释质谱法的简化MDRD方程(MDRD-IDMS方程)、CKD流行病学合作研究方程(CKD-EPI方程)及2个国内简化MDRD改良方程(课题组方程1、2)分别计算eGFR,比较不同估算结果与rGFR的相关性、偏差、精密度以及30％准确性.结果 176例CKD患者的rGFR为[40.70(19.41～84.35)] ml·min-1·(1.73 m2)-1.应用苦味酸法测定肌酐时,各方程评估的eGFR与rGFR的ICC在0.879～0.923之间;应用酶法测定肌酐时,各方程评估的eGFR与rGFR的ICC在0.925 ～0.946之间,相关性优于应用苦味酸法测定肌酐.Bland-Altman图显示,各方程评估的eGFR在高值区偏差较大,但用酶法时偏离程度均小于应用苦味酸法.在rGFR≥60 ml·min-1·(1.73 m2)-1时,各方程应用酶法测定肌酐时的30％准确性在68.3％～90.0％之间,应用苦味酸法30％准确性在41％～75％之间,除课题组方程1外,其他方程应用酶法测定肌酐时的准确性均显著高于苦味酸法.而rGFR＜60ml· min-1·(1.73 m2)-1时,应用酶法、苦味酸法测定肌酐的30％准确性分别在39.7％～49.1％、40.5％～52.6％之间.对于同一方程,应用酶法测定肌酐的两套不同检测系统间,其30％准确性差异无统计学意义,而应用苦味酸法的两套不同检测系统间,其30％准确性差异有统计学意义.结论 同一评估方程使用苦味酸法和酶法两种不同的肌酐检测方法时,结果存在显著性差异.采用酶法测定肌酐时,方程评估的eGFR结果在相关性、偏离程度、准确性方面均优于苦味酸法.     

A new tool for predicting the probability of chronic kidney disease from a specific value of estimated GFR

Abstract

Objective. To demonstrate how patients’ probability of having chronic kidney disease (CKD) stage 3–5 (measured GFR <60 mL/min/1.73 m²) can be predicted from a specific value of estimated glomerular filtration rate (eGFR). Material and methods. The probability of CKD stage 3–5 was predicted from a logistic regression model (n = 850) using three different eGFR prediction equations: Lund-Malmö, MDRD and CKD-EPI. Population weighting was used to illustrate how this probability varies in three different populations: original sample (55% true prevalence of CKD stage 3–5), a screening (6.7% prevalence) and a CKD population (84% prevalence). Results. All three eGFR-equations had high classification ability (area under the receiver-operating-characteristic curve = 97%). The probability of CKD stage 3–5 increased with decreasing eGFR, varied substantially among the populations studied and to some extent between the eGFR-equations. Using the Lund-Malmö equation as illustration, the probability of CKD stage 3–5 is > 90% only when eGFR is <38 mL/min/1.73 m² in a screening population, whereas it is > 90% already when eGFR is <51 mL/min/1.73 m² in a CKD population. Conversely, the probability of CKD stage 3–5 is <10% if eGFR > 59 mL/min/1.73 m² in a screening population, whereas it is <10% only when eGFR is > 88 mL/min/1.73 m² in a CKD population. Conclusion. Instead of reporting diagnostic accuracy as sensitivity, specificity, and predictive values, actual eGFR supplemented with the probability that it represents a true GFR <60 mL/min/1.73 m² may be more valuable for physicians. Clinical (pre-test) probability in the population must be considered when predicting this probability.     

Assessment of the CKD-EPI equation to estimate glomerular filtration rate in adults from a Chinese CKD population

The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation was introduced to estimate glomerular filtration rate (GFR) in chronic kidney disease (CKD) patients based on serum creatinine. The CKD-EPI equation shows better accuracy compared with the current gold standard equation, the Modification of Diet in Renal Disease (MDRD) equation, but it has not been externally validated in Chinese patients. This study compared the CKD-EPI equation with the original MDRD equation and two Chinese MDRD-based equations for estimating GFR in 200 Chinese CKD patients. The (99m)Tc-diethylenetriamine penta-acetate ((99m)Tc-DTPA) method was used to determine actual GFR. The CKD-EPI equation produced GFR estimates that were more consistent with the (99m)Tc-DTPA GFR than did the MDRD equations. The precision and accuracy of the CKD-EPI equation were significantly higher than those of the MDRD equations. In conclusion, the CKD-EPI equation was superior to the existing MDRD equations in terms of estimating GFR and we recommend its clinical use in Chinese CKD patients.     

The role of serum cystatin C in estimation of renal function in survivors of critical illness

PurposeEstimating renal function by serum creatinine after critical illness is a challenging problem. However, the role of cystatin C for estimation of the renal function in survivors of critical illness is unknown. We aimed to compare the performance of serum cystatin C- and serum creatinine-based eGFR against a reference GFR using ^99mTc–diethylenetriaminepentaacetic acid (^99mTc-DTPA) in survivors of critical illness.Material and methodsSurvivors of critical illness with stable hemodynamics and renal functions were recruited. Their serum creatinine and cystatin C levels were measured. eGFR were calculated by using various equations: 1)CKD-EPI SCysC; 2) Thai eGFR SCysC; 3)CKD-EPI SCr; 4)Thai eGFR SCr; 5)MDRD Caucasian SCr; 6)CKD-EPI SCr-SCysC. The ^99mTc-DTPA plasma clearance was used as a standard eGFR.ResultsForty-two patients were included. The bias (median percentage difference) between standard GFR and SCysC-based eGFR were 41.97% (95%CI 33.1% to 48.5%) for CKD-EPI SCysC and 31.72% (95%CI 21.1% to 34.9%) for Thai eGFR SCysC. While, the bias between standard GFR and SCr-based eGFR were −11.37 (95%CI -20.9 to 1.6) for CKD-EPI SCr, −18.30 (95%CI -26.3 to −10.6) for Thai eGFR SCr, and −27.17 (−43.7 to −19.1) for MDRD Caucasian SCr.ConclusionIn survivors of critical illness, we demonstrated limitations of estimating GFR by both currently available SCysC and SCr-based equations. Therefore, further studies are still needed to develop better eGFR equations.     

不同eGFR公式与ACR联合应用在肾功能损伤高危人群中的临床价值

目的探讨不同估算肾小球滤过率(eGFR)公式与尿白蛋白/肌酐比值(ACR)联合应用对高危人群肾功能损伤或早期肾功能降低的检出价值。方法收集850例慢性肾病(CKD)患者的临床资料,包括性别、年龄、身高、体质量、血清肌酐(SCr)、血清胱抑素C(Cys C)、ACR、血清尿素、血清尿酸(UA)、基于99m锝-二乙烯三胺五乙酸(99mTC-DTPA)肾动态显像法的测量肾小球滤过率(mGFR)及基础病史等。分别采用3种基于SCr的eGFR公式(CKD-EPI 2009SCr公式、简化MDRD方程和改良MDRD方程)、6种基于Cys C的eGFR公式(CKD-EPI 2012Cys C公式、Grubb公式、Arnal-Dade公式、Rule公式、Macisaac公式、Tan公式)和1种基于Cys C、SCr联合检测的eGFR公式(CKD-EPI 2012SCr-Cys C公式)计算eGFR。采用Spearman相关分析评估不同eGFR结果之间及与mGFR之间的相关性。采用Bland-Altman一致性分析评价eGFR与mGFR的一致性。结果男、女性CKD患者基于SCr的eGFR水平均高于mGFR(P<0.01),基于Cys C的eGFR水平均低于mGFR(P<0.01)。基于SCr的eGFR结果之间、基于Cys C的eGFR结果之间以及各eGFR结果与mGFR之间均呈正相关(P<0.01)。基于SCr的3种eGFR公式计算出的eGFR与mGFR的平均偏差为-4.2~-20.8 mL/(min·1.73 m2),高估了患者的肾小球滤过率(GFR);基于Cys C的6种eGFR公式计算出的eGFR与mGFR的平均偏差为3.7~16.9 mL/(min·1.73 m2),低估了患者的GFR;基于SCr与Cys C联合检测的eGFR公式计算出的eGFR与mGFR的平均偏差为9.6 mL/(min·1.73 m2),低估了患者的GFR。对于eGFRCKD-EPI 2009SCr漏检的G2期患者,eGFRMacisaac和ACR可分别检出79.2%和55.8%的患者,二者联合应用可检出87.7%的患者;对于eGFRCKD-EPI 2009SCr漏检的G3期~G5期患者,eGFRMacisaac和ACR可分别检出43.3%和61.1%的患者,二者联合使用可检出73.3%的患者。在G2期患者中,eGFRCKD-EPI 2009SCr、eGFRMacisaac和ACR联合应用可将检出率提高至94.4%;在G3期~G5期患者中,可提高至91.7%。结论eGFRCKD-EPI 2009Scr、eGFRMacisaac和ACR联合应用可以显著提高高危人群中肾功能损伤及早期肾功能下降者的检出率。     

Improved glomerular filtration rate estimation using New equations combined with standardized cystatin C and creatinine in Chinese adult chronic kidney disease patients

ObjectivesThe newly developed glomerular filtration rate (GFR)-estimating equations developed by the CKD-EPI Collaboration and Feng et al. (2013) that are based on standardized serum cystatin C (ScysC), combined/not combined with serum creatinine (Scr), require further validation in China. We compared the performance of four new equations (CKD-EPI_cys, CKD-EPI_cr-cys, Feng_cys, and Feng_cr-cys equations) with the CKD-EPI creatinine equation (CKD-EPI_cr) in adult Chinese chronic kidney disease (CKD) patients to clarify their clinical application.Design and MethodsGFR was measured using the dual plasma sampling ^99mTc-DTPA method (mGFR) in 252 adult CKD patients enrolled from four centres. Scr and ScysC were measured by standardized assays in a central laboratory. Each equation's performance was assessed using bias, precision, accuracy, agreement, and correct classification of the CKD stage.ResultsThe measured GFR was 46 [25–83] mL/min per 1.73 m². The CKD-EPI_cys, CKD-EPI_cr-cys and Feng_cys equations provided significantly higher accuracy (P₁₅: 38.9%, 39.7%, and 38.9%) than the CKD-EPI_cr equation (29.8%). The CKD-EPI_cr-cys and Feng_cr-cys equations presented higher precision (IQR of the difference, 16.4 and 17.3 mL/min per 1.73 m², respectively) and narrower acceptable limits in Bland–Altman analysis (56.6 and 50.8 mL/min per 1.73 m², respectively) than single marker-based equations. The CKD-EPI_cr-cys equation achieved the highest overall correct proportion (61.5%) in classification of CKD stages.ConclusionsCombining ScysC and Scr measurements for GFR estimation improves diagnostic performance. The Scr–ScysC equation showed better performance than equations based on either marker alone. The CKD-EPI_cr-cys equation showed the best performance for GFR estimation in Chinese adult CKD patients.     

Low rates of automatic reporting of estimated glomerular filtration rate in Southern Brazilian laboratories

ObjectivesThe aim of this study was to evaluate the rate of eGFR reporting in Southern Brazilian laboratories.Design and methodsThe eGFR automatic reporting, as assessed by Modification of Diet in Renal Disease (MDRD) and/or Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine-based equations, was evaluated in a representative cross-sectional sample. A standardized questionnaire to obtain this information was given out by mail or email.ResultsFive-hundred fifty laboratories, evenly distributed in the different state regions, completed the questionnaire. The eGFR was automatically reported by 54 (9.8%) laboratories, and the MDRD was the most commonly used equation (94.5%). The Jaffe methods were the most employed technique (94%) to measure serum creatinine.ConclusionThe automatic eGFR reporting rate was unacceptably low, emphasizing the crucial role of educating medical teams and laboratories on the importance of having these tools available to optimize detection of renal disease and proper treatment.     

CystatinC在评价CKD患者肾小球滤过功能中的作用

目的比较血清胱抑素c（CystatfnC）、血清肌酐（Scr）、肌酐清除率（Ccr）在慢性肾病（CKD）患者各期与简化MDRD方程估算的肾小球滤过率（eGFR）的符合率。方法血清胱抑索c采用免疫透射比浊法测定,scr和尿肌酐采用酶法测定。估算的eGFR采用简化MDRD方程进行计算。CKD患者临床分期采用美国NFK—K／DOQI指南分期。结果109例CKD患者各期CystatinC、Scr随eGFR的降低而逐渐升高,Ccr随eGFR的降低而逐渐降低,三者在各期间水平的差异均有统计学意义（P〈0．05）。当eGFR≤29ml／min时。CystatinC、Scr、Ccr均为100％的异常,CystatinC、Scr平均水平是参考范围上限的5倍左右,ccr下降4—6倍,三者呈平行性改变;在eGFR30—59ml／min组,CystatinC、Scr、Ccr的平均水平分别为2．54mg／L、144．6gmol／L和50．6ml／min,异常率分别为95％、83％和85％,三者之间异常率的差异无统计学意义（P〉0．05）;在eGFR60．89ml／min组,cvs—tatinC、Ccr异常率为84％和63％,Scr异常率为5．9％,三者之间异常率的差异具有统计学意义（P〈0．05）;在eGFR≥90m1／min组,CystatinC、Ccr异常率为5l％和40％,Scr异常率为l％。结论eGFR〈59ml／min时,CystatlnC、scr、Ccr的结果一致好,与诂算的结果符合率高,基本可以诊断肾小球滤过功能中度下降;当eGFR在60。89ml／min时,CystatinC、Ccr可以检出2／3患者肾小球滤过率的异常,且CystatinC更敏感,而scr不能反应肾小球滤过功能的下降;当eGFR≥90ml／min时,MDRD方程过高估计eGFR值,需检测CystafinC和Ccr以及时发现eGFR的下降。     

Comparison of Two Creatinine-Based Estimating Equations in Predicting All-Cause and Cardiovascular Mortality in Patients With Type 2 Diabetes

OBJECTIVE

To compare the performance of two glomerular filtration rate (GFR)-estimating equations in predicting the risk of all-cause and cardiovascular mortality in type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

We followed 2,823 type 2 diabetic outpatients for a period of 6 years for the occurrence of all-cause and cardiovascular mortality. GFR was estimated using the four-variable Modification of Diet in Renal Disease (MDRD) study equation and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation.

RESULTS

At baseline, an estimated GFR (eGFR) <60 mL/min/1.73 m² was present in 22.0 and 20.2% of patients using the MDRD study equation and the CKD-EPI equation, respectively. A total of 309 patients died during the follow-up (152 patients from cardiovascular causes). Both creatinine-based equations were associated with an increased risk of all-cause and cardiovascular mortality. However, the CKD-EPI equation provided a more accurate risk prediction of mortality than the MDRD study equation. Receiving operating characteristic curves showed that the areas under the curve (AUCs) for all-cause mortality (AUC 0.712 [95% CI 0.682–0.741]) and cardiovascular mortality (0.771 [0.734–0.808]) using eGFR_CKD-EPI were significantly greater (P < 0.0001 by the z statistic) than those obtained by using eGFR_MDRD (0.679 [0.647–0.711] for all-cause mortality and 0.739 [0.698–0.783] for cardiovascular mortality).

CONCLUSIONS

Our findings suggest that the estimation of GFR using the CKD-EPI equation more appropriately stratifies patients with type 2 diabetes according to the risk of all-cause and cardiovascular mortality compared with the MDRD study equation.Chronic kidney disease (CKD) is a major public health problem because its prevalence is rapidly increasing worldwide and it is strongly associated with increased risks of end-stage renal disease, death, cardiovascular disease (CVD), and hospitalization (1–5). Glomerular filtration rate (GFR) is the best overall measure of kidney function. Current diagnosis, evaluation, and management of CKD routinely rely on estimates of GFR (eGFRs) usually derived from creatinine-based equations such as the Modification of Diet in Renal Disease (MDRD) study equation, which incorporates information on serum creatinine concentration, age, sex, and race (1,6,7). This equation is the most commonly used method for estimating kidney function in routine clinical practice. Its prognostic value has been validated in several studies and populations (1,6,7). Decreased eGFR_MDRD has been shown to be an important risk factor for death, CVD events, and other adverse clinical outcomes, specifically in patients with a GFR level <60 mL/min/1.73 m² (1–5). However, despite its widespread use, it is known that the major limitations of the MDRD study equation are imprecision and systematic underestimation of measured GFR (bias) at higher values (1,6,7).The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) investigators recently developed and validated a new equation to improve the estimation of GFR (eGFR_CKD-EPI) by using a large database pooled from 10 studies (8). This equation, which uses the same four variables as the MDRD study equation (i.e., serum creatinine level, age, sex, and race), has been shown to be more precise and accurate than the MDRD study equation in estimating measured GFR, especially at higher GFR values (8). Improved accuracy of the CKD-EPI equation could have important implications for public health and clinical practice (8). In addition, some large population-based cohort studies have recently shown that the CKD-EPI equation also has superior accuracy in classifying individuals at risk for CVD events and death compared with the MDRD study equation (9–11).However, the CKD-EPI equation might not work equally well in people at high CVD risk, such as type 2 diabetic individuals. Whether the use of the CKD-EPI equation provides more accurate prognostic information than the MDRD study equation with respect to the risk of all-cause and CVD mortality in patients with type 2 diabetes is currently unknown. Thus, the aim of this prospective, longitudinal study was to compare the performance of the MDRD study equation and the CKD-EPI equation in predicting all-cause and CVD mortality in a large sample of type 2 diabetic individuals during a follow-up period of 6 years.     

Glomerular filtration rate estimation and mortality in an elderly population

BACKGROUND: Few studies have addressed the link between minor renal dysfunction and mortality in the elderly. AIM: To compare three equations for estimated GFR (eGFR) in assessing renal dysfunction and predicting mortality in an elderly population. DESIGN: Longitudinal observational study. METHODS: We studied 441 people from the Jerusalem Seventy Year Olds Longitudinal Study who had measurements of serum creatinine, all of whom were aged 70 years at study initiation and were living in the community. GFR was estimated based on serum creatinine and using the Cockcroft-Gault (CG), the abbreviated Modification of Diet in Renal Disease (MDRD) and the Mayo Clinic equations. Twelve-year mortality was the main outcome measure. RESULTS: The prevalence of reduced eGFR was 51% using the CG, 34% using MDRD and 16% using the Mayo Clinic equation. eGFR dichotomized by the definition of CKD significantly predicted mortality only with the Mayo Clinic equation (hazard ratio 1.56, 95%CI 1.01-2.39). When eGFR was divided into quartiles and the lowest compared to the highest, all equations predicted mortality. Hazard ratios (95%CI) were 5.48 (1.27-23.65), 7.47 (2.74-20.3), and 7.375 (3.13-17.36), for CG, MDRD, and Mayo Clinic, respectively. DISCUSSION: Reduced eGFR was prevalent in this study group, and associated with mortality. This association was strongest using the Mayo Clinic equation.