7种肾小球滤过率评估方程在慢性肾脏病患者中的比较

目的：比较不同肾小球滤过率（GFR）评估方程在慢性肾脏病（CKD）患者中的诊断价值。方法：选择CKD各期患者108例,对照20例,应用ELISA法测定血清Cystatin C浓度、^99m Tc-DTPA清除率测定GFR、全自动生化分析仪检测血清肌酐（Scr）,并用7种公式计算GFR（eGFR）。结果：在CKD2期,MDRD、简化MDRD与GFR比较有统计学差异,在CKD3期,CG-eGFR与GFR比较有统计学差异。而Cys-eGFR在CKD1～5期与GFR均无统计学差异。在CKD2期、3期,4种Cys-eGFR方程与GFR的相关性均显著优于CG和MDRD公式。而在1期、4期和5期,各方法测定eGFR与同位素GFR的相关性相当。在GFR〈60ml.min^-1.1.73m^-2的CKD患者中,4种Cys-eGFR的ROC曲线下面积大于Cr-eGFR方程,有统计学意义;在GFR〈30ml.min^-1.1.73m^-2的CKD患者中,ROC曲线下面积比较无统计学差异。结论：cys-eGFR在肾功能轻中度减退的患者中,优于CG和MDRD,在肾衰竭后期,诊断价值同Cr-eGFR公式。     

不同肾功能评估公式在PAP酶法肌酐检测时临床适用性比较

目的：探讨不同肾小球滤过率（GFR）计算公式在肾功能评估中的差异。方法：以99mTc-DTPA肾动态显像法检测的GFR（rGFR）为参照值,对263例符合CKD入选标准的患者采用PAP酶法检测Scr,并对CG公式、MDRD公式、简化MDRD公式和中国人改良MDRD公式（C-MDRD）进行偏离度、精确度和准确性比较。结果：rGFR与CG、MDRD、简化MDRD和C-MDRD估测的eGFR均呈显著相关,r分别是0.821、0.870、0.856、0.856（均P〈0.001）。4种公式的偏离度分别是1221.04、2172.12、2518.45和7295.78,绝对偏差的中位数分别是：14.57、12.48、14.44和25.55;C-MDRD公式与其他3种公式有统计学差异（P〈0.001）,30%准确性分别是60.5%、61.2%、56.3%和38.8%。结论：本组患者行CG、MDRD、简化MDRD和C-MDRD公式估测的eGFR与rGFR相关性好;在PAP酶法测定肌酐条件下,综合偏离度、精确度和准确性分析,MDRD公式临床适用性最佳,而C-MDRD公式最差。     

中国肾小球滤过率评估方程在慢性肾小球肾炎患者的适用性评价

目的：评价现有在中国人群基础上开发的肾小球滤过率（GFR）评估方程在慢性肾小球肾炎患者的适用性。方法：选择143例慢性肾小球肾炎患者,用中国方程、瑞金方程、MDRD1方程和简化MDRD方程,分别计算GFR值,与^99mTc—DTPA测的GFR（sGFR）进行比较。结果：Bland—Altman分析显示MDRD1方程和瑞金方程估计的GFR和sGFR的一致性较好,但所有各方程估计的GFR和出FR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,MDRD1方程和瑞金方程估测的GFR与X轴的斜率较其他方程更接近0。在所有方程中,MDRD1方程和中国9方程偏差较小,瑞金方程估测GFR30％符合率和50％符合率均最高,但瑞金方程估测GFR30％符合率依然低于70％。在慢性肾脏病不同分期中,瑞金方程和MDRD1方程较其他方程有较小的偏差和更优的准确性。结论：当血肌酐的测定方法为酶法时,如直接应用现有在中国人群基础上开发的肾小球滤过率评估方程评估慢性肾小球肾炎患者肾功能,可能会产生明显的偏差。     

不同肾小球滤过率评估方程在慢性肾脏病患者中适用性的比较

目的：比较肾脏病膳食改良试验（MDRD）和Cock—croft—Gault（cG）方程以及国内的两个校正MDRD方程对慢性肾脏病（CKD）患者预测肾小球滤过率（GFR）的适用性。方法：选择2006年--2008年646例非透析CKD患者,用简化MDRD和CG公式以及两个国内校正公式（MDRD1、MDRD2）计算估测GFR（eGFR）,并进行相关性、偏离度、精密度的比较,以及比较不同CKD分期估测GFR的准确性、偏差中位数。结果：（1）MDRD1方程不论在精密度、偏离度、绝对偏差方面都明显优于其他的方程。（2）MDRD1方程的30％和50％准确率上明显高于其他方程（P〈0．05）。（3）CG明显低估了GFR,MI）RD和MDRD2在Ⅳ期低估了GFR,在Ⅱ、Ⅲ期高估了GFR,MDRD1在Ⅲ期高估了GFR。结论：经过校正的MDRD1方程明显优于CG、简化MDRD、MDRD2方程。     

不同公式估算慢性肾脏病患者肾小球滤过率的结果评价

目的探讨不同估算公式估算慢性肾脏病（CKD）患者肾小球滤过率（GFR）在肾功能评价中的价值。方法选择CKD患者239例,所有患者同步检测99锝-二乙烯三胺五乙酸（^99mTc-DTPA）、GFR、血肌酐（SCr）等。将^99mTc-DTPA测定的GFR作为参照,并用肾脏病膳食改良试验（MDRD）公式、Cockcroft-Gault公式、简化MDRD公式及慢性肾脏病流行病合作研究（cKD-EPI）公式计算估测GFR,比较不同CKD分期中各估算公式估算的GFR的准确性。结果各估算公式估算的GFR值均高于^99mTc-DTPA,MDRD公式偏离程度最大;各估算公式估算的GFR值与^99mTc-DTPA检查的GFR结果有相关性,CKD-EPI公式相关性最高。结论CKD-EPI公式估算肾功能更接近^99mTc-DTPA的结果,但仍需进一步校正。     

2型糖尿病肾病患者血清淀粉样蛋白A水平

目的：探讨2型糖尿病肾病患者的血清淀粉样蛋白A（SAA）水平。方法：2型糖尿病患者144例,依据尿白蛋白排泄率（UAER）结果分为单纯糖尿病组（SDM组）：UAER〈30mg/24h;糖尿病肾病组（DN组）：UAER≥30mg/24h。DN组依据肾小球滤过率（GFR）水平分为两组,DN早中期组（EDN组）：GFR〉30ml·min^-1·1.73m^-2;DN中晚期非透析组（LDN组）：GFR≤30ml·min^-1·1.73m^-2。同时入选正常对照组（NC组）30例。测定血清SAA水平,进行多因素分析。结果：DN组SAA水平较SDM组显著升高（P〈0.05）;SDM组SAA水平较NC组显著升高（P〈0.05）;LDN组SAA水平较NC组、SDM组、EDN组显著升高（均P〈0.01）。SAA水平与尿白蛋白、腰臀比呈正相关。结论：2型糖尿病肾病患者血清SAA水平明显升高,并与DN严重程度密切相关。     

不同方法对肾功能评估的价值

目的探讨临床上常用的几种肾功能评估方法的相对准确性,寻求更为简便、快捷的肾功能评估方法。方法选择慢性肾脏病（CKD）患者80例,分别用^99mTc-DTPA肾动态显像法测定肾小球滤过率（GFR）,同时检测患者血肌酐（SCr）、血清胱抑素C（CysC）浓度,根据SCr分别用Cock-croft-Gault（C-G）方程和简化MDRD方程估算肾小球滤过率（分别为eGFR1、eGFR2）。按GFR值将患者分为4组,即A组：CKD1期;B组：CKD2期;C组：CKD3期;D组：CKD4期;排除CKD5期的患者。观察所有和各组患者eGFR1、eGFR2、SCr、CysC与GFR的相关性。结果总样本中,eGFR1、eGFR2与GFR呈正相关,SCr、CysC与GFR呈负相关（P〈0．01）。在各组中,A组：eGFR1、eGFR2、SCr与GFR之间均无明显相关性（P〉0．05）;而B、C、D组中eGFR1、eGFR2与GFR呈正相关（P〈0．01）,SCr与GFR呈负相关（P〈0．05）;CysC在A、B、C、D各组中均与GFR呈负相关（P〈0．01）。结论CKD2、3、4期患者eGFR1、eGFR2、SCr与GFR均有一定的相关性,但不论何期CKD患者,CysC均能准确反映其肾功能状况,且更加简便、快捷。     

三种肾小球滤过率检测方法的实用性探讨

目的：以^99mTc—DPTA血浆清除率为标准，对24h内生肌酐清除率（Ccr）、Cookeroft—Gault（CG）方程和简化MDRD（modification of diet in renal disease）方程进行比较，评价三种方程在慢性肾脏疾病（CKD）患者中的应用。方法：选择139例各种慢性肾脏疾病患者，将Ccr、CG方程和简化MDRM方程估算的肾小球滤过率（GFR）用体表面积（BSA）标准化，与BSA标准化的^99mTc—DTPA测得的GFR（^99mTc—GFR）在不同CKD分期进行比较。结果：CKD第一至第五期：Ccr与^99mTc—GFR相关系数r分别为：0．79、0．71、0．64、0．59、0．52；Ccr在ROC曲线下面积平均为0．79。CG—GFR与^99mTc—GFR相关系数r分别为：0．85、0．78、0．72、0．67、0．61；CG—GFR在ROC曲线下面积平均为0．83。MDRD—GFR与^99mTc—GFR相关系数r分别为：0．83、0．76、0．69、0．65、0．59；MDRD—GFR在ROC曲线下面积平均为0．82。在CKD不同分期三种方程的GFR估算值与^99mTc—GFR差异均有显著意义（P均〈0．001）。结论：三种方程的GFR估算值与^99mTc—GFR均有较好的相关性和ROC曲线下面积，以CG方程最好，其次为简化MDRD方程，Ccr最低，但三种方程估算值与^99mTc—GFR测定值差异均有显著意义。上述方程直接应用于我国CKD患者时，应对其进行适当修正。     

血糖水平对糖尿病患者肾小球滤过率估算公式的影响

目的 评价糖尿病患者血糖水平对肾小球滤过率（GFR）公式估算结果的影响;比较不同血糖水平Cockcroft-Gault（CG）公式和MDRD公式法估算GFR对诊断肾功能不全的差异。 方法 选取1210例糖尿病患者,同步检测99mTc-GFR（iGFR）、Scr和糖化血红蛋白（HbA1c）。运用CG和MDRD公式计算GFR估计值（eGFRCG、 eGFRMDRD）。依据肾脏病透析预后质量指南（K/DOQI）的建议将糖尿病患者分为iGFR正常组589例[NGFR组,iGFR≥90 ml&#8226;min-1&#8226;(1.73 m2)-1],iGFR轻度下降组[GGFR组,60≤iGFR<90 ml&#8226;min-1&#8226;(1.73 m2)-1]470例,iGFR中度下降组[MGFR组,30≤iGFR<60 ml&#8226;min-1&#8226;(1.73 m2)-1]151例。根据HbA1c的四分位点（7.1%,10.5%）分为4组（<7.1%、7.1%~8.6%、8.7%~10.4%、≥10.5%）,其中HbA1c<7.1%者定义为血糖控制较好组,HbA1c≥10.5%定义为血糖控制差组。采用Spearman相关分析、t检验、Bland-Altman分析、受试者工作特征（ROC）曲线等评估方程的偏离度、准确度,以及血糖对估算结果的影响。 结果 eGFRMDRD在各GFR亚组中均高估GFR;eGFRCG在NGFR组中低估GFR,差异有统计学意义。Bland-Altman分析结果显示,血糖控制较差组的eGFRMDRD的偏差高于血糖控制较好组的eGFRMDRD;血糖控制较差组的eGFRMDRD15%和30%准确性低于血糖控制较好组的eGFRMDRD,差异有统计学意义。血糖控制较差组和较好组间eGFRCG偏差及准确性差异均无统计学意义;而eGFRCG的偏差高于eGFRMDRD,差异有统计学意义。血糖控制良好组CG公式和MDRD公式在诊断肾功能不全患者的ROC曲线下面积差异无统计学意义。血糖控制较差组eGFRMDRD ROC曲线下面积显著大于eGFRCG曲线下面积,差异有统计学意义。 结论 糖尿病患者采用MDRD和CG公式法可导致GFR估计差误。MDRD公式的eGFR估计值受到血糖的影响较大,MDRD公式法高估GFR。MDRD公式在血糖控制较差的患者对肾功能不全患者的估算效应要优于CG公式。     

六种肾小球滤过率估算方程对梗阻性肾病患者肾小球滤过率的比较

目的:比较六种肾小球滤过率估算方程在评价中国梗阻性肾病患者肾小球滤过率(Glomerular filtration rate,GFR)的适用性,即3种MDRD(Modification of Diet in Renal Disease,MDRD)公式和3种CKD-EPI(Chronic Kidney Disease Epidemiology Collaboration,CKD-EPI)公式。方法:选择2012年01月~2016年12月在我院完成99 m Tc-DTPA肾动态显像(ECT)检查的梗阻性肾病患者476例,以ECT所测得的GFR(m GFR)作为参考标准,用目前常用以上6种方程估算GFR(e GFR)为对照,分析各e GFR与m GFR的相关性,并就6种e GFR的估测偏差、精确度、准确率及诊断准确性进行比较。结果:本研究结果表明各e GFR与m GFR均显示高度的相关性(P0.01)。在数值诊断上,各e GFR与CKD-EPI联合方程e GFR间的估测偏差、精确度、15%、30%及50%范围的准确度比较差异有统计学意义(P0.05)。CKD-EPI方程较MDRD方程显示出较好的数值准确度,CKD-EPI联合方程所估算的GFR在数值上准确度最高。在诊断方面,3种CKD-EPI方程的ROC曲线下面积、分期诊断准确度及其一致性比3种MDRD方程更好,其中,CKD-EPI联合方程ROC曲线下面积最大(0.886),分期诊断准确度最高(44.1%),Kappa值最大(0.254,CI[0.179,0.311])。在亚组分析中,不同的亚组最适方程有所差别,其中简化MDRD与CKD-EPI联合方程在不同亚组中的适用性较高。结论:CKD-EPI方程对中国的梗阻性肾病患者较MDRD方程有更高的适用性,其中CKD-EPI联合方程所估算的e GFR值与m GFR值相关性最好,准确度最高,偏倚最小,诊断性能最好。     

Does the ID-MS traceable MDRD equation work and is it suitable for use with compensated Jaffe and enzymatic creatinine assays?

BACKGROUND: International recommendations suggest that measurement of serum creatinine should be supplemented with an estimate of glomerular filtration rate (GFR) using the Modification of Diet in Renal Disease (MDRD) study equation. One problem has been the lack of standardization of commercially available creatinine assays resulting in varying estimates of GFR. A revision of the MDRD equation offers traceability to a reference method. This study evaluates the use of isotope dilution mass spectrometry (ID-MS), the compensated Jaffe and enzymatic creatinine methods compared with the Beckman CX3 Jaffe assay used to derive the MDRD equation and investigates their impact on GFR estimation using both the original and ID-MS-traceable MDRD equations. METHODS: Serum creatinine was measured in 277 patients by (i) ID-MS, (ii) a Roche enzymatic assay, (iii) a Roche compensated kinetic Jaffe assay and (iv) a Beckman CX3 kinetic Jaffe assay. Estimated GFR was calculated using the MDRD equations. RESULTS: The ID-MS (-7.5%), Roche enzymatic (-8.6%) and compensated kinetic Jaffe (-11.9%) assays were all negatively biased (P < 0.0001) compared with the Beckman CX3 assay, causing predictable, clinically significant, overestimation of GFR when the original MDRD equation is used. This positive bias was reduced (ID-MS 6.7 to 0.4%; enzymatic 8.8 to 3.4%; compensated kinetic Jaffe 13.7 to 7.1%) when GFRs were calculated using the ID-MS-traceable MDRD equation. CONCLUSIONS: Compensated assays that account for non-creatinine chromogen interference produce significantly higher estimates of GFR when using the original MDRD equation. Use of the ID-MS-traceable MDRD equation ameliorates this effect. There is good agreement between estimated GFR derived from the original MDRD equation using Beckman Astra CX3 data and estimated GFR derived from the new ID-MS-traceable MDRD equation using a local ID-MS creatinine assay. This suggests that the ID-MS-traceable MDRD equation may be reliably used with both ID-MS and true ID-MS-traceable creatinine assays without the requirement for standardization to the MDRD laboratory.     

The importance of standardization of creatinine in the implementation of guidelines and recommendations for CKD: implications for CKD management programmes.

BACKGROUND: In an attempt to reduce late referral and to improve the care of patients with chronic kidney disease (CKD), different organizations have issued guidelines on when to refer patients to the nephrologist. Most suggest referral of patients with a GFR below 60 ml/min/1.73 m2, and demand referral if the GFR is below 30 ml/min/1.73 m2. It is recommended to use the abbreviated MDRD equation to estimate GFR. This formula is, however, sensitive to the creatinine assay methodology. In addition, the impact of the implementation of such guidelines on the nephrology practice has never been evaluated. This study (i) identifies the true burden of CKD in a population and simulates the effects of a 100% implementation of the guidelines on the nephrology work load, and (ii) evaluates the validity of the estimated GFR using the abbreviated MDRD formula when routinely provided. METHODS: Different laboratories (both hospital and private) in our region were asked to report on all the serum creatinine values performed during the first week of December 2004. If patients had more than one determination, only the lowest serum creatinine value was retained. Patients already known to a nephrology unit were not included. GFR was calculated using the abbreviated MDRD, using the serum creatinine as reported by these laboratories, or after correction to the MDRD-standard using different published equations. RESULTS: 20,108 patients, with a mean age of 53.4+/-16.2 years, 48% females, had at least one serum creatinine determination in the observation period. According to the K/DOQI CKD classification, 20.2, 1.6 and 0.8% of females and 13.3, 1.6 and 0.6% of males were in stage 3, 4 and 5, respectively, when the abbreviated MDRD formula was used with the serum creatinine value as reported by the laboratories. Important differences in classifications were obtained when the different correction formulae for creatinine were applied. According to the current recommendations, this would lead to a mandatory referral of 1650-2400 CKD stage 4 patients per 100 000 inhabitants and a suggested referral of another 4100-15 360 CKD stage 3 patients per 100,000 inhabitants to a nephrology unit. CONCLUSION: Implementation of the current guidelines for referral of CKD patients to nephrologists would lead to an overload of the nephrology care capacities. Large differences in estimated GFRs with different corrections for serum creatinine are observed, resulting in important CKD classification differences. Standardization of serum creatinine assays is mandatory before guidelines, and especially the routine provision of the estimated GFR by the abbreviated MDRD formula, can be implemented in clinical practice.     

Evaluation of the equations to estimate the glomerular filtration rate in kidney transplant recipients

This study assessed the performance of three methods for estimating glomerular filtration rate (GFR) in kidney transplant patients: the Cockcroft-Gault formula, the modification of diet in renal disease (MDRD) method, and the four-variable modification of diet in renal disease (four-variable MDRD), both as an overall estimate and as related to clinical disease stage. We analyzed data from 136 renal transplant patients including 84 men in an overall age range of 28 to 76 years. Patients were categorized into three groups according to GFR as determined by the arithmetical mean of the last four creatinine clearance determinations after outlying values had been excluded: group 1, estimated GFR of <30 mL/min (n = 26); group 2, estimated GFR of 30 to 60 mL/min (n = 63);, and group 3, estimated GFR >60 mL/min (n = 33). Fourteen patients were excluded from the analysis because of a high variability between their creatinine clearance determinations. Estimated GFRs using the Cockroft-Gault, MDRD, and four-variable MDRD formulae were compared with GFRs as measured by creatinine clearance. Statistically significant correlations were observed for all three formulae for the overall series and for individual clinical groups. Hence, we concluded that all equations had a similar capacity to predict the GFR. In addition, because of the clear, significant correlation between the MDRD and the four-variable MDRD (r = .992; P = .0001), we believe that the four-variable MDRD can substitute for the MDRD for clinical purposes.     

Evaluation of creatinine-based estimates of glomerular filtration rate in a large cohort of living kidney donors

BACKGROUND: Accurate determination of kidney function is critical in the evaluation of living kidney donors and higher donor glomerular filtration rate (GFR) is associated with better allograft outcomes. However, among transplant centers donor kidney function evaluation varies widely. METHODS: The performance of creatinine clearance (CrCl), Modification of Diet in Renal Disease (MDRD), the re-expressed MDRD equations with standardized creatinine, and the Cockcroft-Gault (CG) formula as compared with (125)I-iothalamate GFR (iGFR) was analyzed in 423 donors. All methods of GFR measurement were then evaluated for their association with graft function at 1 year. RESULTS: The MDRD and re-expressed MDRD equations underestimated iGFR whereas CG showed minimal bias (median difference=-11.0, -16.3, and -0.5 mL/min/1.73 m(2), respectively). CrCl overestimated iGFR (10 mL/min/1.73 m(2)). The MDRD, re-expressed MDRD, and CG formulas were more accurate (88%, 86%, and 88% of estimates within 30% of iGFR, respectively) than CrCl (80% within 30% of iGFR). Interestingly, low bias and high accuracy were achieved by averaging the MDRD estimation with the CrCl result; both methods available to the clinician in most transplant centers. We also showed that predonation GFR as measured by isotopic renal clearance or any of the creatinine-based estimation formulas may be associated with allograft function at 1 year, whereas the widely used CrCl was not. CONCLUSIONS: Variable performance was seen among different GFR estimations, with CrCl being the poorest. Recent recommendations to use the MDRD equation with standardized serum creatinine did not improve its performance. However, recognizing the limited availability of GFR laboratories, these methods are still clinically useful if used with caution and understanding their limitations.     

Modified glomerular filtration rate estimating equation for Chinese patients with chronic kidney disease

The Modification of Diet in Renal Disease (MDRD) equations provide a rapid method of assessing GFR in patients with chronic kidney disease (CKD). However, previous research indicated that modification of these equations is necessary for application in Chinese patients with CKD. The objective of this study was to modify MDRD equations on the basis of the data from the Chinese CKD population and compare the diagnostic performance of the modified MDRD equations with that of the original MDRD equations across CKD stages in a multicenter, cross-sectional study of GFR estimation from plasma creatinine, demographic data, and clinical characteristics. A total of 684 adult patients with CKD, from nine geographic regions of China were selected. A random sample of 454 of these patients were included in the training sample set, and the remaining 230 patients were included in the testing sample set. With the use of the dual plasma sampling (99m)Tc-DTPA plasma clearance method as a reference for GFR measurement, the original MDRD equations were modified by two methods: First, by adding a racial factor for Chinese in the original MDRD equations, and, second, by applying multiple linear regression to the training sample and modifying the coefficient that is associated with each variable in the original MDRD equations and then validating in the testing sample and comparing it with the original MDRD equations. All modified MDRD equations showed significant performance improvement in bias, precision, and accuracy compared with the original MDRD equations, and the percentage of estimated GFR that did not deviate >30% from the reference GFR was >75%. The modified MDRD equations that were based on the Chinese patients with CKD offered significant advantages in different CKD stages and could be applied in clinical practice, at least in Chinese patients with CKD.     

Estimating the glomerular filtration rate using serum cystatin C levels in patients with spinal cord injuries

Study design:Prospective cohort study.Objectives:To investigate the relationship between (51)chromium-ethylene-diamine-tetra-acetate ((51)Cr-EDTA) clearance, serum cystatin C (CysC), serum creatinine, creatinine clearance and estimated glomerular filtration rate (eGFR(MDRD), MDRD stands for modification of diet in renal disease) based on the serum creatinine in patients with complete or incomplete spinal cord injury (SCI) and to develop and evaluate a GFR-estimating equation using serum CysC.Settings:Spinal Cord Injury Unit, Viborg Regional Hospital, Viborg, Denmark.Methods:Ninety-eight men and 47 women with SCI were included in the study. Serum CysC levels were measured by an automated particle-enhanced nephelometric immunoassay, serum and urine creatinine levels were measured by an enzymatic method traceable to the IDMS creatinine reference method, and (51)Cr-EDTA clearance was measured by a multiple plasma sample method.Results:The area under the curves (AUCs) in the non-parametric receiver operating characteristics (ROC) plots for serum CysC were compared with serum creatinine and to eGFR(MDRD) and revealed a significant difference (P-value<0.05) for all SCI patients. There was no significant difference between the AUC for serum CysC compared with the AUC for creatinine clearance. GFR (ml?min(-1) per 1.73?m(2)) can be calculated from serum CysC values (mg?l(-1)) using the equation eGFR(CysC)=212·exp(0.914·CysC). The model accurately predicted the GFR of 88% of patients within ±30% of the measured GFR, and it was able to predict the GFR of 50% of patients within ±10% of the measured GFR.Conclusion:In patients with SCI, GFR can be estimated independent of age, sex and muscle mass by a newly developed equation based on a single serum CysC value.     

Utility of Estimated Glomerular Filtration Rate Equations in Assessing Renal Allograft Function: Are They Accurate?

Creatinine clearance (CrCl) is more accurate than other methods when assessing renal allograft function, but it is inconvenient for patients. In clinical practice, renal allograft function is often estimated using estimated glomerular filtration rate (GFR) equations. This cross-sectional study compared agreement between CrCl and serum creatinine–based equations among renal transplant recipients (RTRs) attending a transplant clinic in a tertiary center. Six equations (Cockcroft-Gault, Walser's, Nankivell, abbreviated Modification of Diet in Renal Disease [MDRD], Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI], and European Kidney Function Consortium[EKFC]) were included in the analysis. The bias, precision, and accuracy of each equation were determined. Correlation analysis was performed by determining the correlation coefficient and plotting Bland-Altmann plots. A total of 165 subjects were included in this study. Mean serum creatinine was 112.03 ± 38.67 µmol/L, and mean CrCl was 58.44 ± 21.24 mL/min/1.73 m². Walser's equation showed strongest correlation, lowest bias, and highest accuracy of the proportion of estimated GFR falling within ±30% of CrCl, followed by the 4-variable MDRD equation. All 6 equations systematically underestimated GFR among RTRs. Walser's equation showed the best estimation of GFR, suggesting that it may be the formula of choice to estimate GFR among RTRs.     

Kidney function estimating equations: where do we stand?

PURPOSE OF REVIEW: Estimation of the glomerular filtration rate (GFR) is central to the diagnosis, evaluation and management of chronic kidney disease. This review summarizes recent data on the performance of equations using serum creatinine to estimate the GFR, particularly the Modification of Diet in Renal Disease (MDRD) Study equation. RECENT FINDINGS: During 2005 GFR estimation has received substantial attention with a focus on comparing the MDRD Study equation with the Cockcroft-Gault equation. Several large studies (n>500) have appeared. Most studies discuss creatinine calibration but few were able to standardize measurements. Studies that did calibrate the creatinine had improved performance. Overall, the MDRD Study equation performed well in populations with a low range of GFR and often outperformed the Cockcroft-Gault equation. Both equations have lower precision in high GFR populations, and the MDRD equation under-estimated the GFR in a number of studies. Efforts are underway to develop improved prediction equations by pooling data across many study populations. SUMMARY: Equations for estimating the GFR from serum creatinine are useful for systematic staging of chronic kidney disease. The MDRD Study equation and systematic creatinine assay calibration improve the level of precision and accuracy in many settings. GFR estimates are less useful in the normal range of GFR, however, and are sensitive to the population under study.     

Estimation of glomerular filtration rate in South Asian healthy adult kidney donors

Aim:   We evaluated the performance of serum creatinine based equations to estimate glomerular filtration rate (GFR) in South Asian healthy renal donors.
Methods:   GFR by 99mTc-diethylenetriamine pentaacetic acid (DTPA) renogram (mGFR) in 599 renal donors was measured. GFR was estimated using a six variable modification of diet in renal disease formula (MDRD1), a four variable MDRD formula (MDRD2), Cockcroft-Gault creatinine clearance (CG CrCl), Cockcroft-Gault glomerular filtration rate (CG GFR) and the Mayo Clinic formula (Mayo GFR). The performance of various prediction equations was compared for global bias, precision (R²) and accuracy (percentage of estimated GFR (eGFR) falling within 15% and 30% of mGFR).
Results:   The mean age was 37.4 ± 11 years and 48.2% were male. The mGFR was 95.5 ± 11.6 mL/min per 1.73 m². The bias (mL/min per 1.73 m²) was 7.5 ± 0.9, −9.0 ± 0.75, 13.1 ± 0.9, 7.5 ± 0.9 and 23.4 ± 0.76 for CG CrCl, CG GFR, MDRD1, MDRD2 and Mayo GFR, respectively. R² was 0.082 for CG CrCl and MDRD1, 0.081 for CG GFR and MDRD2 and 0.045 for Mayo GFR. The percentages of eGFR falling within 15% and 30% of mGFR were 50.5 and 80.1 for CG CrCl, 65.8 and 84 for CG GFR, 50 and 74 for MDRD1, 54.3 and 80.1 for MDRD2 and 32 and 63.4 for Mayo GFR. Overall CG GFR performed better in estimating GFR in all subjects.
Conclusion:   The CG GFR equation was better than other equations to estimate GFR in South Asian healthy renal donors. We propose a new equation derived from the regression model in our study population to estimate GFR in a South Asian healthy adult population.