三种肾小球滤过率检测方法与99mTc-DTPA清除率的比较与分析

目的为临床准确评估肾小球滤过率（GFR）提供一定依据。方法对101例各种慢性肾脏病患者,外周静脉注射非离子型造影剂碘海醇（iohexol）5ml,4h后取血2ml,用高效液相色谱（HPLC）法检测血浆iohexol浓度。运用数字模型计算血浆iohexol清除率（iohexol-GFR）。同步检测Scr及^99mTc—DTPA清除率（^99mTc—GFR）。应用Cockcroft—Gait（CG）、肾脏病膳食改良试验（MDRD）公式计算Ccr、GFR。以^99mTc—GFR为标准,运用相关回归分析及受试者工作曲线（ROC）对上述指标进行比较。结果慢性肾脏病第1期至第5期,iohexol—GFR与^99mTc-GFR相关系数r分别为0．87、0．89、0．88、0．86、0．87（P均〈0．01）;iohexol—GFR在ROC曲线下面积平均为0．97。MDRD—GFR与^99mTc—GFR相关系数r分别为0．80、0．75、0．71、0．67、0．56（P均〈0．01）,MDRD—GFR在ROC曲线下面积平均为0．82。CG—Ccr与^99mTc—GFR相关系数r分别为0．76、0．67、0．62、0．60、0．53（P均〈0．05）,CG—Ccr在ROC曲线下面积平均为0-82。结论iohexol—GFR检测GFR的准确性优于MDRD—GFR、CG—Ccr,值得推广应用。在无检测条件的情况下,CG、MDRD公式不失为衡量GFR的良好指标。     

血清胱抑素C评价慢性肾脏病患者早期肾损害的临床研究

目的:探讨血清胱抑素C(CystatinC,CystC)在评价慢性肾脏病患者早期肾功能损害的临床价值。方法:收集自2005年7月～2006年2月住院的慢性肾脏病患者88例,采用乳胶颗粒增强免疫透射比浊分析法(PETIA)测定血清CystC浓度,同时测定血清肌酐浓度(Scr,碱性苦味酸法)及内生肌酐清除率(Ccr,标准24h留尿计算法),以99mTc-二乙三胺五醋酸(99mTc-DTPA)法测得的肾小球滤过率(GFR)作为诊断评价的金标准,比较CystC、Scr、Ccr与GFR的相关性。采用受试者工作特征曲线下面积(AUCROC)和似然比(LR)评价CystC的可靠性。结果:患者血清CystC、Ccr、Scr与GFR均呈显著相关(P<0.01),以CystC与GFR的相关程度最密切;上述3个指标AUCROC分别为0.980、0.941、0.914,且CystC与Scr之间具有统计学意义(P<0.05),而与Ccr间无统计学差异(P>0.05),LR以血清CystC为最佳。结论:与Ccr和Scr相比,血清CystC是一个更为准确、可靠的反映肾小球滤过功能的指标,对早期诊断慢性肾脏病患者肾小球滤过功能的损害具有重要价值。     

血清胱抑素C对糖尿病肾病早期诊断的意义

目的：评价血清胱抑素C（Cys-C）,对糖尿病肾病患者早期诊断的价值。方法：应用颗粒增强免疫比浊法测定50例健康体检者和198例糖尿病患者的Cys-C、血清肌酐（Scr）、β2微球蛋白（β2-MG）浓度,同时测量198例患者尿肌酐（UCr）、尿微量白蛋白（MAlb）根据尿量计算出内生肌酐清除率（Ccr）以及24h尿微量白蛋白,并进行比较分析。结果：早期糖尿病肾病组Cys-C（1.63±0.87）、β2-MG（2.60±1.07）和临床糖尿病肾病组的Cys-C（2.29±1.18）、β2-MG（3.19±1.43）均较单纯糖尿病组Cys-C（0.91±0.21）、β2-MG（1.59±0.42）和正常对照组的检测结果明显增高,差异有统计学意义（P〈0.01）;单纯糖尿病组Cys-C、β2-MG、Scr和Ccr检测结果和正常对照组比较差异无统计学意义。早期糖尿病肾病组中,Cys-C、β2-MG和Ccr、Scr阳性率分别为75.4%（46/61）、88.5%（54/61）、32.8%（20/61）、4.9%（3/61）;临床糖尿病肾病组中,Cys-C、β2-MG和Ccr、Scr阳性率分别为87.5%（49/56）、91.1%（51/56）、66.1%（37/56）、50%（28/56）。Cys-C与β2-MG的相关系数,差异有统计学意义（r=0.8418,P〈0.01）。结论：胱抑素C用于评价糖尿病患者的肾功能状况,其特异性好于β2-MG,灵敏度高于Ccr、Scr,是的一个能较好反映肾小球滤过率的指标,对糖尿病肾病早期诊断具有重要的临床意义。     

血清胱抑素C在评价慢性肾脏病患者肾小球滤过率中的价值

目的：探讨血清胱抑素C（CystC）在评价慢性肾脏病（CKD）患者肾小球滤过率中的临床价值。方法：选取2009年4月～2009年11月住院的CKD患者76例,检测其血清CystC浓度,血清肌酐浓度（Scr）,以99mTc-二乙三胺五醋酸（99mTc-DTPA）法测定肾小球滤过率（GFR）,并用简化MDRD和Cockcroft-Gault（C-G）方程分别估测GFR（M-GFR,C-GFR）,以99mTc-GFR作为金标准,比较不同CKD分期间各指标间的相关性及其敏感度和特异度。结果：患者血清CystC、Scr、C-GFR、M-GFR与99mTc-GFR的相关系数分别为-0.81、-0.73、0.90、0.89,P均〈0.01,CystC在CKD1～3期与99mTc-GFR均有相关性,相关系数分别为-0.57（P〈0.05）,-0.44（P〈0.05）,-0.74（P〈0.01）,但在4～5期两者无明显相关关系（相关系数-0.30,P〉0.05）而Scr、C-GFR、M-GFR与99mTc-GFR仅在CKD3期患者中有相关性;在CKD1期患者中,CystC的敏感性和特异性均高于C-GFR和M-GFR。结论：血清CystC是一个反映CKD患者肾功能的较为敏感的指标,尤其在早期CKD患者中应用价值更大。     

肾动态显像中不同本底的选取在重度肾功能不全患者肾小球滤过率的评估

目的 以99mTc-DTPA血浆清除率为标准，评价在重度肾功能不全[GFR≤30 ml·min-1·（1.73 m2)-1]患者GFR的评估中,本底矫正在提高99mTc-DTPA肾动态显像检查准确性中的价值。 方法 选择重度慢性肾脏病患者33例,年龄均>20岁，男性/女性=13/20,平均Scr 334 μmol/L，诊断均符合美国NKF-K／DOQI关于慢性肾脏病定义。排除肾功能急性恶化因素、水肿、肢体缺如及心功能不全。分别检测患者身高、体质量。常规99mTc-DTPA肾动态功能显像，采用双肾下极（传统Gates法，a法）及肾周环形勾画法（b法）获取图像本底，并分别由计算机自动计算GFR值（GFRa和GFRb）。于注射后2 h、4 h各抽血4 ml,离心后取血浆1 ml，测量其放射性计数。计算99mTc-DTPA的血浆清除率（双血浆法, GFRp）作为GFR标准。所测数值均用体表面积标准化。肾动态显像两种不同方法求得的GFRa和 GFRb值分别与99mTc-DTPA的血浆清除率进行比较。 结果 两种方法，即Gates法、肾周环形本底法，所得的GFR测量值与99mTc-DTPA的血浆清除率(GFRp)比较：相关系数（ra、rb）分别为0.602、0.834；偏差中位数分别为8.33、-4.41；绝对偏差中位数分别为8.33、4.49。GFRa和GFRb落在GFRp±15%、 ±30%和±50%范围内的病例百分数分别为24.2%、30.3%和48.5%及33.3%、51.5%和81.8%。 结论 在重度肾功能不全患者肾小球滤过率的评估中，传统的Gates法明显高估了患者实际的GFR值，而肾周环形本底的选取能明显提高传统Gates法的准确性，可能具有临床推广的价值。     

以血清胱抑素C评价早期肾功能损害的临床研究

目的:评价血清胱抑素C(Cystatin C)在早期肾功能损害诊断中的临床意义.方法:应用ELISA法测定84例各种肾脏病患者的血清胱抑素C浓度,同时测定血清肌酐(Scr,Jaffe法)及肌酐清除率(Ccr),以放射性核素99m Tc-DTPA测得的GFR作为诊断评价的金指标,比较Cystatin C、Scr、Ccr与GFR的相关性,采用受试者工作特征曲线下面积(AUCROC)和似然比(LR)评价Cystatin C的可靠性.结果:血清Cystatin C、Scr、Ccr与GFR均呈显著相关(P<0.01),且以Cystatin C与GFR的相关程度最密切;上述三个指标AUCROC分别为0.989、0.926、0.942,且Cystatin C与Scr之间具有显著统计学意义(P<0.05),而与Ccr间无统计学差异(P>0.05),LR以血清Cystatin C为最佳.结论:血清Cystatin C 是一个更为准确、可靠的反映肾小球滤过功能的指标,对诊断各种不同肾脏病患者早期肾功能损害具有指导意义.     

血清CysC、B2-MG评价慢性肾脏病患者早期肾功能损害

目的探讨血清半胱氨酸蛋白酶抑制剂C（CystC）、B2微球蛋白（胆-MG）在评价慢性肾脏病（CKD）患者早期肾功能损害中的临床价值。方法收集2008年2月至2009年1月问包头市中心医院。肾内科住院CKD患者116例,根据肾小球滤过率（GFR）,分为3组,即A组为肾功能正常组,GFR≥90ml·min-1。·（1．73m2）-1;B组为早期肾功能不全组,60ml·min-1。·（1．73m2）-1≤GFR〈90ml·min-1·（1．73m2）-1;C组为中晚期。肾功能不全组,GFR％60ml·min。·（1．73m2）～。测定不同肾功能时期CysC、132-MG、SCr、尿素氮（BUN）水平,各组间进行比较,并与GFR进行相关性比较,采用受试者工作特征曲线下面积,评价CysC、132-MG的可靠性。结果患者血清CysC、G2-MG、SCr、尿素氮（BUN）与GFR均呈显著相关（P〈0．01）,且以CysC与GFR的相关程度最密切,CysC、82-MG、SCr、尿素氮（BUN）受试者曲线下面积分别是0．989、0．983、0．877、0．873。结论CysC、胆-MG成为理想的反应GFR的内源性指标。通过联合检测血清CysC和B32-MG水平可以为评价GFR提供敏感、对早期诊断各种慢性肾脏病患者肾小球滤过功能的损害具有重要价值。     

非离子型造影剂iohexol血浆清除率单点检测法测定肾小球滤过率

目的：用非离子型造影剂iohexol血浆清除率检测肾小球滤过率（GFR）。方法：选择93例各种肾脏病患者，男45例，女48例，年龄12－80岁，清晨空腹注射iohexol 5ml,4h后留取血样，高效液相（HPLC）法检测血浆iohexol浓度，应用Jacobsson和Bubeck两种一室分布的数学模型，计算iohexol血浆清除率，以^99mTc-GFR作为检测GFR的金标准，对两者进行比较。结果：Jacobsson法算得iohexol－GFR与^99mTc-GFR相关系数为r=0.85,标准误为16．06ml/min;Bubeck法算得iohexol－GFR与^99mTc-GFR相关系数为r=0.82,标准误为17．75ml/min。在早期肾功能不全的患者中，iohexol－GFR较Scr、Ccr能更敏感反映肾功能减退。结论：应用Jacobsson和Bubeck两种模型单点法计算iohexol血浆清除率是检测GFR的简便、准确的方法。     

99mTc-DTPA肾动态显像检测肾小球滤过率的临床应用评价

目的 以^99mTc-DTPA血浆清除率为标准，评价^99mTc-DTPA肾动态显像检查在检测肾小球滤过率(GFR)中的应用价值。方法 选择慢性肾脏病患者197例，年龄均>18岁，诊断均符合美国NKF-K/DOQI关于慢性肾脏病定义。排除肾功能急性恶化因素、水肿、肢体缺如、心功能不全。记录身高、体重。肘静脉“弹丸”式注射^99mTc-DTPA 111 MBq后即刻行肾动态图像采集120 帧，计算双肾GFR，即Gates法，同时于注射后2、4 h各抽血4 ml，分离血浆1 ml，测量其放射性计数，计算99mTc-DTPA的血浆清除率(双血浆法)，所测数值均用体表面积标准化。按双血浆法所测得的GFR值将患者分成3组:A组 77例，GFR < 30 ml·min^-1·(1.73 m²)^-1；B组 74例， 30 ml·min^-1·(1.73 m²)^-1≤GFR < 90 ml·min^-1·(1.73 m²)^-1；C组 46例，GFR≥90 ml·min^-1·(1.73 m²)^-1。分别行肾动态显像法与双血浆法所测值之间的相关分析。 结果 肾动态显像法及双血浆法所测3组GFR[单位:ml·min^-1·(1.73 m²)^-1]分别为:A组 (27.08±12.14) 比 (17.68±5.66)；B组 (63.18±23.59) 比 (51.95±16.81)； C组 (107.28±27.36) 比 (117.96±24.17)。2者间的相关系数分别为rA=0.286(P=0.012)；rB=0.804(P < 0.01)；rC=0.473(P < 0.01)。结论 99mTc-DTPA肾动态显像检查适用于轻、中度肾功能不全患者GFR的评估，但在重度肾功能不全患者中，其测量结果的准确性有待进一步提高。     

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。     

The plasma creatinine concentration is not an accurate reflection of the glomerular filtration rate in stable renal transplant patients receiving cyclosporine

We studied 31 stable renal cadaver kidney transplant patients receiving cyclosporine (CyA) and prednisone for immunosuppression to determine what reduction in true glomerular filtration rate (GFR) was reflected by their mild elevation in plasma creatinine concentration (1.8 +/- 0.11 mg/dL). We measured both the creatinine clearance (60 +/- 4.32 mL/min/1.73 m2) and the true GFR using Technetium 99m-DTPA (44 +/- 2.72 mL/min/1.73 m2). The creatinine clearance overestimated true GRF by a mean of 38%, indicating that this percentage of creatinine reached the urine by tubular secretion rather than glomerular filtration. A similar degree of overestimation was found in a separate group of 14 patients receiving imuran for immunosuppression. In 23 patients receiving CyA in whom the serum creatinine concentration was less than 2.0 mg/dL, the mean DTPA clearance was 49.5 +/- 2.83 mL/min/1.73 m2. In stable renal transplant patients receiving CyA, a serum creatinine concentration at, or close to, the upper limit of the normal range may reflect markedly impaired renal function.     

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.     

持续非卧床腹膜透析患者血清肌酐水平的影响因素分析

目的：探讨影响持续非卧床腹膜透析（CAPD）患者血清肌酐水平的因素。方法：选取北京大学第三医院腹透中心200名临床情况稳定的CAPD患者为研究对象。同时收集患者人口学特征、血清肌酐（Scr）及其他生化资料,评估腹膜透析充分性,采用简单相关及多元回归分析探讨影响Scr水平的因素。结果：所有患者平均年龄（61.02±14.81）岁,平均Scr（893±293）μmol/L;简单相关分析显示Scr水平与年龄、总尿素清除指数（TKt/V）、残肾尿素清除指数（RKt/V）、总肌酐清除率（Tccr）及残肾肌酐清除率（Rccr）呈负相关,而与透析剂量、体质指数（BMI）、透析龄呈正相关,差异均具有统计学意义;逐步多元回归分析提示在矫正透析剂量、透析龄及糖尿病等因素后,性别、年龄、Tccr、RKt/V、透析液肌酐浓度/血肌酐浓度（D/PCr）及BMI是影响Scr水平的独立因素（R2=0.659,P〈0.05）。结论：本研究提示在剂量、透析龄及糖尿病等因素后,性别、年龄、营养状况、残余肾功能及腹膜转运功能仍能独立地影响CAPD患者血清肌酐水平。     

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.     

Assessment of glomerular filtration rate in healthy subjects and normoalbuminuric diabetic patients: validity of a new (MDRD) prediction equation.

BACKGROUND: Based on the data derived from the Modification of Diet in Renal Disease (MDRD) study, a new equation was developed for the estimation of glomerular filtration rate (GFR). This equation, which takes into account body weight, age, sex, serum creatinine, race, serum urea, and serum albumin, provided a more accurate estimation of GFR in patients with renal insufficiency. However, this prediction equation has not been validated in subjects with normal or supra-normal GFR. METHODS: In a cross-sectional study, we measured GFR by inulin clearance in 46 healthy controls and 46 non-complicated type 1 diabetic patients. In this study population, GFR was predicted by measured creatinine clearance, the Cockcroft-Gault formula, and the MDRD equation. RESULTS: In the healthy subjects, mean GFR (+/-SD) was 107+/-11 as compared to 122+/-18 ml/min per 1.73 m(2) in the diabetic patients. This difference in GFR was reflected by a lower serum creatinine (76+/-8 vs 71+/-8 micro mol/l) in the diabetic patients. In the healthy controls, median absolute differences (and the 50th-75th-90th percentile of percentage absolute differences) between predicted and measured GFR were 5.2 ml/min per 1.73 m(2) (4.9-9.8-18.5%) for creatinine clearance, 9.0 ml/min per 1.73 m(2) (8.6-14.3-24.6%) for the Cockcroft-Gault formula, and 10.7 ml/min per 1.73 m(2) (10.9-16.3-25.5%) for the MDRD equation. In the diabetic patients, these differences were 8.3 ml/min per 1.73 m(2) (7.6-9.3-13.0%) for creatinine clearance; 11.8 ml/min per 1.73 m(2) (10.1-16.0-22.5%) for the Cockcroft-Gault formula, and 18.8 ml/min per 1.73 m(2) (16.0-24.2-31.9%) for the MDRD equation. CONCLUSIONS: In subjects with a normal or increased GFR, the new MDRD-prediction equation of GFR is less accurate than creatinine clearance or the Cockcroft-Gault formula, and offers no advantage.     

Serum cystatin C as an endogenous marker of renal function in patients with mild to moderate impairment of kidney function.

BACKGROUND: Estimation of the glomerular filtration rate (GFR) is essential for the evaluation of patients with chronic kidney disease (CKD). Recently, serum cystatin C was proposed as a new endogenous marker of GFR and in our study its diagnostic accuracy was compared with that of other markers of GFR. METHODS: In this study, 164 patients with CKD stages 2-3 (GFR 30-89 ml/min/1.73 m2), who had performed 51Cr-labelled ethylenediaminetetra-acetic acid clearance, were enrolled. In each patient, serum creatinine and serum cystatin C were determined. Creatinine clearance was calculated using the Cockcroft-Gault (C&G) and the modification of diet in renal disease (MDRD) formulas. RESULTS: The mean 51CrEDTA clearance was 57 ml/min/1.73 m2, the mean serum creatinine 149 micromol/l and the mean serum cystatin C 1.74 mg/l. We found significant correlation between 51CrEDTA clearance and serum creatinine (R = -0.666), serum cystatin C (R = -0.792), reciprocal of serum creatinine (R = 0.628), reciprocal of serum cystatin C (R = 0.753) and calculated creatinine clearance from the formulas C&G (R = 0.515) and MDRD formulas (R = 0.716). The receiver operating characteristic (ROC) curve analysis (cut-off for GFR 60 ml/min/1.73 m2) showed that serum cystatin C had a significantly higher diagnostic accuracy than serum creatinine (P = 0.04) and calculated creatinine clearance from the C&G formula (P < 0.0001), though only in female patients. No difference in diagnostic accuracy was found between serum cystatin C and creatinine clearance calculated from the MDRD formula. CONCLUSIONS: Our results indicate that serum cystatin C is a reliable marker of GFR in patients with mildly to moderately impaired kidney function and has a higher diagnostic accuracy than serum creatinine and calculated creatinine clearance from the C&G formula in female patients.     

Prediction of glomerular filtration rate in renal transplant recipients: cystatin C or Modification of Diet in Renal Disease equation?

BACKGROUND: To overcome disadvantages of serum creatinine two strategies have been suggested to identify patients with reduced glomerular filtration rate (GFR). On the one hand, the Modification of Diet in Renal Disease (MDRD) equation is now recommended to classify the stage of chronic kidney disease. On the other hand, cystatin C (Cys C) has been investigated in numerous studies, finding a higher sensitivity than creatinine in detecting diminished GFR. To date, no comparison of both strategies in patients after renal transplantation has been performed. METHODS: One hundred and five consecutive renal transplant recipients underwent (99m)Tc-DTPA-- clearance measurement. Simultaneously, MDRD estimates were calculated and Cys C serum levels were determined. ROC analyses were performed at different decision points from 20 to 70 mL/min/1.73 m(2). RESULTS: Although the area under the curve did not differ significantly between MDRD and Cys C within the tested GFR range, the AUC for Cys C tended to be higher when GFR exceeded 55 mL/min/1.73 m(2). A significantly higher diagnostic accuracy for Cys C compared with MDRD (p = 0.045 at 65 mL/min/1.73 m(2)) was found when investigating the subgroup of patients with well-functioning grafts (GFR>40 mL/min/1.73 m(2)). CONCLUSION: MDRD equation is equivalent to Cys C measurement in renal transplant recipients. As availability of MDRD is superior to Cys C, we recommend GFR estimation using the MDRD equation. Nevertheless, Cys C may serve as a confirmation test of high MDRD estimates in patients with well-functioning grafts because of superior accuracy in these patients.     

Serum creatinine is a poor marker of GFR in nephrotic syndrome.

BACKGROUND: In daily clinical practice creatinine clearance is used as marker of glomerular filtration rate (GFR). As a result of the tubular secretion process endogenous creatinine clearance (ECC) overestimates glomerular filtration rate, particularly in patients with impaired renal function. It has been suggested that the tubular handling of creatinine is altered in patients with a nephrotic syndrome. METHODS: Inulin clearance (GFR) and creatinine clearance (ECC) have been simultaneously measured in a cohort of 42 patients with proteinuria and 45 healthy controls. The clearance of creatinine by tubular secretion (TScreat) can be estimated by ECC-GFR. TScreat was calculated in both groups. Regression analysis was performed to identify factors that independently influence tubular creatinine secretion. RESULTS: The mean age (+/-SD) of the patients was 41+/-13 years, serum albumin 26+/-9 g/l, median (IQR) proteinuria 4.5 (3.6-8.2) g/10 mmol creatinine, serum creatinine 103 (84-143) micromol/l, ECC 85 (69-118) ml/min/1.73 m2, and GFR 54 (36-83) ml/min/1.73 m2. Median TScreat amounted to 29 (21-36) ml/min/1.73 m2. In the healthy controls serum creatinine was 75 (70-81) micromol/l, ECC 118 (109-125) ml/min/1.73 m2, GFR 106 (102-115) ml/min/1.73 m2, and TScreat 11 (3.5-19) ml/min/1.73 m2. By regression analysis serum albumin was identified as an independent predictor of tubular creatinine secretion. We divided the patients in two subgroups based on serum albumin levels. TScreat was 24 (14-29) ml/min/1.73 m2 in patients with serum albumin levels >25.8 g/l, and 36 (28-54) ml/min/1.73 m2 in patients with serum albumin levels <25.8 g/l (P<0.01). CONCLUSION: Serum albumin levels influence tubular creatinine secretion. As a result, the endogenous creatinine clearance as well as estimated GFR using a modified MDRD equation more pronouncedly overestimate glomerular filtration rate in nephrotic syndrome.     

Comparison between creatinine and cystatin C-based GFR equations in renal transplantation.

BACKGROUND: Estimation of glomerular filtration rate (GFR) from serum creatinine (Scr) or cystatin C (Cys C) exhibit variable performances. METHODS: We compared the performances of 14 Scr and 9 Cys C estimated GFR equations using inulin clearance (Clin) as the reference test in 103 stable renal transplant populations. Bias, precision, receiving operation characteristics (ROC), accuracy within 30% ranges from the reference method and agreements of each test were compared. RESULTS: Mean Clin was 46.4+/-20.9 ml/min/1.73 m2. Scr and Cys C levels correlated well with each other (r=0.83, P<0.0001) and with Clin (r=-0.57 and -0.53, P<0.001, respectively). ROC analysis demonstrated no superiority of Cys C over Scr. Gats equation achieved the highest accuracy of 70% in patients with GFR>or=60 ml/min/1.73 m2. In patients with GFR>or=60 ml/min/1.73 m2, the Nankivell equation demonstrated the highest accuracy of 73.91%. Cys C-based equations were not depicted to be thoroughly accurate. Bias, precision and agreement were otherwise similar in all GFR tests. CONCLUSION: Scr-based equations did not appear to be inferior to Cys C-based equations as a means to estimate GFR in renal transplant patients.     

Assessment of glomerular filtration rate in transplant recipients with severe renal insufficiency by Nankivell,Modification of Diet in Renal Disease (MDRD), and Cockroft-Gault equations

Measurement of glomerular filtration rate (GFR) is time consuming and cumbersome. Several formulas have been developed to predict creatinine clearance (CrCl) or GFR using serum creatinine (Cr) concentrations and demographic characteristics. However, few studies have been performed to discern the best formula to estimate GFR in kidney transplantation. In this study, Cockroft-Gault (CG), Nankivell, and Levey (MDRD) formulas were tested to predict GFR in 125 cadaveric renal transplant patients with severe renal insufficiency (GFR less than 30 mL/min per 1.73 m2). The GFR was estimated as the average Cr and urea clearances. The mean GFR estimated by averaged Cr and urea clearances (22.18+/-5.23 mL/min per 1.73 m2) was significantly different from the mean values yielded by the MDRD formula (20.42+/-6.65 mL/min per 1.73 m2, P=.000), the Nankivell formula (30.14+/-11.98 mL/min per 1.73 m2, P=.000), and the CG formula (29.42+/-8.64 mL/min per 1.73 m2, P=.000). The MDRD formula showed a better correlation (R=0.741, P=.000) than the CG (R=0.698, P=.000) and the Nankivell formulas (R=0.685, P=.000). Analysis of differences using the Bland-Altmann method demonstrated that MDRD gave the lowest bias (MDRD: -1.65+/-4.4 mL/min per 1.73 m2; CG: 7.33+/-6.24 mL/min per 1.73 m2; Nankivell: 8.05+/-9.23 mL/min per 1.73 m2) and narrower limits of agreement (Nankivell: -10.41-26.51 mL/min per 1.73 m2; CG: -5.15-19.81 mL/min per 1.73 m2; MDRD: -10.61-7.31 mL/min per 1.73 m2). In transplant patients with severe renal insufficiency, the MDRD equation seems better than the other formulas to estimate GFR.