Performance of the modification of diet in renal disease and Cockcroft-Gault equations in the estimation of GFR in health and in chronic kidney disease

The performance of the Modification of Diet in Renal Disease (MDRD) and the Cockcroft-Gault (CG) equations as compared with measured (125)I-iothalamate GFR (iGFR) was analyzed in patients with chronic kidney disease (CKD) and in potential kidney donors. All outpatients (n = 1285) who underwent an iGFR between 1996 and 2003 were considered for analysis. Of these, 828 patients had CKD and 457 were potential kidney donors. Special emphasis was put on the calibration of the serum creatinine measurements. In CKD patients with GFR <60 ml/min per 1.73 m(2), the MDRD equation performed better than the CG formula with respect to bias (-0.5 versus 3.5 ml/min per 1.73 m(2), respectively) and accuracy within 30% (71 versus 60%, respectively) and 50% (89 versus 77%, respectively). Similar results are reported for 249 CKD patients with diabetes. In the kidney donor group, the MDRD equation significantly underestimated the measured GFR when compared with the CG formula, with a bias of -9.0 versus 1.9 ml/min per 1.73 m(2), respectively (P < 0.01), and both the MDRD and CG equations overestimated the strength of the association of GFR with measured serum creatinine. The present data add further validation of the MDRD equation in outpatients with moderate to advanced kidney disease as well as in those with diabetic nephropathy but suggest that its use is problematic in healthy individuals. This study also emphasizes the complexity of laboratory calibration of serum creatinine measurements, a determining factor when estimating GFR in both healthy individuals and CKD patients with preserved GFR.     

The practical implications of using standardized estimation equations in calculating the prevalence of chronic kidney disease.

BACKGROUND: Kidney Disease Outcomes Quality Initiative (KDOQI) chronic kidney disease (CKD) guidelines have focused on the utility of using the modified four-variable MDRD equation (now traceable by isotope dilution mass spectrometry IDMS) in calculating estimated glomerular filtration rates (eGFRs). This study assesses the practical implications of eGFR correction equations on the range of creatinine assays currently used in the UK and further investigates the effect of these equations on the calculated prevalence of CKD in one UK region METHODS: Using simulation, a range of creatinine data (30-300 micromol/l) was generated for male and female patients aged 20-100 years. The maximum differences between the IDMS and MDRD equations for all 14 UK laboratory techniques for serum creatinine measurement were explored with an average of individual eGFRs calculated according to MDRD and IDMS < 60 ml/min/1.73 m(2) and 30 ml/min/1.73 m(2). Similar procedures were applied to 712,540 samples from patients > or = 18 years (reflecting the five methods for serum creatinine measurement utilized in Northern Ireland) to explore, graphically, maximum differences in assays. CKD prevalence using both estimation equations was compared using an existing cohort of observed data. RESULTS: Simulated data indicates that the majority of laboratories in the UK have small differences between the IDMS and MDRD methods of eGFR measurement for stages 4 and 5 CKD (where the averaged maximum difference for all laboratory methods was 1.27 ml/min/1.73 m(2) for females and 1.59 ml/min/1.73 m(2) for males). MDRD deviated furthest from the IDMS results for the Endpoint Jaffe method: the maximum difference of 9.93 ml/min/1.73 m(2) for females and 5.42 ml/min/1.73 m(2) for males occurred at extreme ages and in those with eGFR > 30 ml/min/1.73 m(2). Observed data for 93,870 patients yielded a first MDRD eGFR < 60 ml/min/1.73 m(2) in 2001. 66,429 (71%) had a second test > 3 months later of which 47,093 (71%) continued to have an eGFR < 60 ml/min/1.73 m(2). Estimated crude prevalence was 3.97% for laboratory detected CKD in adults using the MDRD equation which fell to 3.69% when applying the IDMS equation. Over 95% of this difference in prevalence was explained by older females with stage 3 CKD (eGFR 30-59 ml/min/1.73 m(2)) close to the stage 2 CKD (eGFR 60-90 ml/min/1.73 m(2)) interface. CONCLUSIONS: Improved accuracy of eGFR is obtainable by using IDMS correction especially in the earlier stages of CKD 1-3. Our data indicates that this improved accuracy could lead to reduced prevalence estimates and potentially a decreased likelihood of onward referral to nephrology services particularly in older females.     

Estimation of glomerular filtration rate by the MDRD study equation modified for Japanese patients with chronic kidney disease

Background

Accurate estimation of the glomerular filtration rate (GFR) is crucial for the detection of chronic kidney disease (CKD). In clinical practice, GFR is estimated from serum creatinine using the Modification of Diet in Renal Disease (MDRD) study equation or the Cockcroft-Gault (CG) equation instead of the time-consuming method of measured clearance for exogenous markers such as inulin. In the present study, the equations originally developed for a Caucasian population were tested in Japanese CKD patients, and modified with the Japanese coefficient determined by the data.

Methods

The abbreviated MDRD study and CG equations were tested in 248 Japanese CKD patients and compared with measured inulin clearance (Cin) and estimated GFR (eGFR). The Japanese coefficient was determined by minimizing the sum of squared errors between eGFR and Cin. Serum creatinine values of the enzyme method in the present study were calibrated to values of the noncompensated Jaffé method by adding 0.207?mg/dl, because the original MDRD study equation was determined by the data for serum creatinine values measured by the noncompensated Jaffé method. The abbreviated MDRD study equation modified with the Japanese coefficient was validated in another set of 269 CKD patients.

Results

There was a significant discrepancy between measured Cin and eGFR by the 1.0 × MDRD or CG equations. The MDRD study equation modified with the Japanese coefficient (0.881 × MDRD) determined for Japanese CKD patients yielded lower mean difference and higher accuracy for GFR estimation. In particular, in Cin 30–59?ml/min per 1.73?m², the mean difference was significantly smaller with the 0.881 × MDRD equation than that with the 1.0 × MDRD study equation (1.9 vs 7.9?ml/min per 1.73?m²; P P 2, the accuracy was significantly higher, with 85% vs 69% of the points deviating within 50% (P P 2.

Conclusions

Although the Japanese coefficient improves the accuracy of GFR estimation of the original MDRD study equation, a new equation is needed for more accurate estimation of GFR in Japanese patients with CKD stages 3 and 4.     

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.     

An alternative formula to the Cockcroft-Gault and the modification of diet in renal diseases formulas in predicting GFR in individuals with type 1 diabetes

Chronic kidney disease is currently on the rise and not only leads to ESRD necessitating dialysis or transplantation but also increases cardiovascular disease risk. Measurement of the GFR, the gold standard for assessing kidney function, is expensive and cumbersome. Several prediction formulas that are based on serum creatinine are currently used to estimate the GFR, but none has been validated in a large cohort of individuals with diabetes. The performance of two commonly used formulas, the abbreviated Modification of Diet in Renal Disease (MDRD) study formula for the GFR and the Cockcroft-Gault estimate of creatinine clearance, were examined against GFR measured by the renal clearance of iothalamate in 1286 individuals with type 1 diabetes from the Diabetes Control and Complications Trial (DCCT). The performance of these formulas was assessed by computing bias, precision, and accuracy. The DCCT participants had normal serum creatinine, unlike the MDRD patients, and somewhat lower creatinine excretion than subjects in the original cohort Cockcroft Gault, which led to biased and highly variable estimates of GFR when these formulas were applied to the DCCT subjects. The MDRD substantially underestimated iothalamate GFR, whereas the Cockcroft Gault formula underestimated it when it was <120 ml/min per 1.73 m(2) and overestimated it when iothalamate GFR was >130 ml/min per 1.73 m(2). Overall, only one third of the formula's estimates were within +/-10% of iothalamate GFR. By underestimating GFR, these formulas were likely to flag early declines in kidney function. Refitting the MDRD formula to the DCCT data gave a more accurate and unbiased prediction of GFR from serum creatinine; percentage of estimate within 10% of measured GFR increased to 56%. A substantial variability in the estimates, however, remained.     

Age- and gender-specific reference values of estimated GFR in Caucasians: the Nijmegen Biomedical Study

The Nijmegen Biomedical Study is a population-based cross-sectional study conducted in the eastern part of the Netherlands. As part of the overall study, we provide reference values of estimated glomerular filtration rate (GFR) for this Caucasian population without expressed risk. Age-stratified, randomly selected inhabitants received a postal questionnaire on lifestyle and medical history. In a large subset of the responders, serum creatinine was measured. The GFR was then measured using the abbreviated Modification of Diet in Renal Disease (MDRD) formula. To limit possible bias, serum creatinine was calibrated against measurements performed in the original MDRD laboratory. The study cohort included 2823 male and 3274 female Caucasian persons aged 18-90 years. A reference population of apparently healthy subjects was selected by excluding persons with known hypertension, diabetes, cardiovascular- or renal diseases. This healthy study cohort included 1660 male subjects and 2072 female subjects, of which 869 of both genders were 65 years or older. The median GFR was 85 ml/min/1.73 m(2) in 30-to 34-year-old men and 83 ml/min/1.73 m(2) in similar aged women. In these healthy persons, GFR declined approximately 0.4 ml/min/year. Our study provides age- and gender-specific reference values of GFR in a population of Caucasian persons without identifiable risk.     

The cost of implementing UK guidelines for the management of chronic kidney disease.

BACKGROUND: Chronic kidney disease (CKD) is a major public health problem. In the UK, guidelines have been developed to facilitate case identification and management. Our aim was to estimate the annualized cost of implementation of the guidelines on newly identified CKD cases. METHODS: We interrogated the New Opportunities for Early Renal Intervention by Computerised Assessment (NEOERICA) database using a Java program created to recompile the CKD guidelines into rule-based decision trees. This categorized all patients with a serum creatinine recorded over a 1-year period into those requiring more tests or referral. A 12-month cost analysis for following the guidelines was performed. RESULTS: In the first year, a practice of 10,000 would identify 147.5 patients with stages 3-5 CKD over and above those already known. All stages 4-5 CKD cases would require nephrology referral. Of those with stage 3 CKD (143.85), 126.27 stable patients would require more tests. The following would require referral: 14.8 with estimated glomerular filtration rate decline>or=5 ml/min/1.73 m2/year, 1.11 with haemoglobin<11 g/dl and 1.67 with blood pressure>150/90 on three anti-hypertensives. The projected cost per practice of investigating stable stage 3 CKD was euro 6111; and euro 7836 for nephrology referral. Total costs of euro 17 133 in the first year were increased to euro 29,790 through the effect of creatinine calibration. CONCLUSIONS: CKD guideline implementation results in significant increases in nephrology referral and additional investigation. These costs could be recouped by delaying dialysis requirement by 1 year in one individual per 10,000 patients managed according to guidelines.     

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.     

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。     

Variation in the serum creatinine assay calibration: a practical application to glomerular filtration rate estimation

BACKGROUND: Variation among clinical laboratories in calibration of serum creatinine assays is a source of error in glomerular filtration rate (GFR) estimation equations. We evaluated impact of this variation on GFR estimates. METHODS: Errors in GFR estimates were computed based on the range of calibration differences from the 1994 College of American Pathologists (CAP) survey using the Modification of Diet in Renal Disease (MDRD) Study GFR equation. RESULTS: Mean (95% CI) calibration difference observed in the CAP survey was +0.14 mg/dL (+12.4 micromol/L) [-0.09, +0.37 mg/dL (-7.96, +32.71 micromol/L)]. Errors in GFR estimates using uncalibrated serum creatinine values were lower in individuals with lower estimated GFR. For GFR of 60 mL/min/1.73 m(2), the mean calibration difference in the CAP survey was associated with errors in GFR estimation between -5.5 to -8.1 mL/min/1.73 m(2) (-9.1 to -13.5%) depending on race and sex. The 95% confidence interval for the calibration difference was associated with a maximal range of error in GFR estimates from +4.6 to -18.1 mL/min/1.73 m(2) (+7.6 to -30.2%). Errors of this magnitude at an estimated GFR of 60 mL/min/1.73 m(2) are not likely to be of clinical significance. However, errors at higher levels of estimated GFR would be greater, making GFR estimates in this range unreliable. CONCLUSION: Recalibration of serum creatinine assays to the MDRD Study clinical laboratory would improve accuracy of GFR estimation using the MDRD Study equation, but is not practical for all clinical laboratories. As an interim solution, clinical laboratories could report GFR estimates <60 mL/min/1.73 m(2) without recalibration with an acceptable accuracy.     

Definition and classification of chronic kidney disease: a position statement from Kidney Disease: Improving Global Outcomes (KDIGO)

Chronic kidney disease (CKD) is a worldwide public health problem, with adverse outcomes of kidney failure, cardiovascular disease (CVD), and premature death. A simple definition and classification of kidney disease is necessary for international development and implementation of clinical practice guidelines. Kidney Disease: Improving Global Outcomes (KDIGO) conducted a survey and sponsored a controversies conference to (1) provide a clear understanding to both the nephrology and nonnephrology communities of the evidence base for the definition and classification recommended by Kidney Disease Quality Outcome Initiative (K/DOQI), (2) develop global consensus for the adoption of a simple definition and classification system, and (3) identify a collaborative research agenda and plan that would improve the evidence base and facilitate implementation of the definition and classification of CKD. The K/DOQI definition and classification were accepted, with clarifications. CKD is defined as kidney damage or glomerular filtration rate (GFR) <60 mL/min/1.73 m(2) for 3 months or more, irrespective of cause. Kidney damage in many kidney diseases can be ascertained by the presence of albuminuria, defined as albumin-to-creatinine ratio >30 mg/g in two of three spot urine specimens. GFR can be estimated from calibrated serum creatinine and estimating equations, such as the Modification of Diet in Renal Disease (MDRD) Study equation or the Cockcroft-Gault formula. Kidney disease severity is classified into five stages according to the level of GFR. Kidney disease treatment by dialysis and transplantation should be noted. Simple, uniform classifications of CKD by cause and by risks for kidney disease progression and CVD should be developed.     

MDRD方程在我国慢性肾脏病患者中的改良和评估

目的开发适合我国慢性肾脏病(CKD)患者的肾小球滤过率(GFR)评估方程。方法收集国内不同地域、肾功能不同分期的CKD患者684例的有关资料。随机选取454例为开发组,230例为验证组。以双血浆法~(99m)Tc-DTPA血浆清除率为GFR参考值。(1)在简化MDRD方程中添加种族系数；(2)多元逐步回归线法开发新的GFR评估方程；(3)将上述两种改良的方程与改良前简化MDRD方程进行偏离度、精确度、准确性比较。结果684例患者中,男352例,女332例,平均年龄(49．9±15．8)岁。上述两种改良的简化MDRD方程在肾功能不同分期内偏离度分别为543．0、677．2和2175．0任意单位；精确度分别为57．5、56．5和60．7 ml·min~(-1)·(1．73 m~2)~(-1)；准确性均优于改良前简化MDRD方程,差异有统计学意义(30%的准确性由66．1%提高至77．8%和79．6%,P＜0．05)。结论基于我国CKD人群特点,改良的简化MDRD方程与改良前方程相比,表现了显著的优势,可以替代改良前简化MDRD方程,应用于我国CKD患者的GFR评估。     

Comparison of the Mayo Clinic Quadratic Equation with the Modification of Diet in Renal Disease equation and radionuclide glomerular filtration rate in a clinical setting

Background: Recent guidelines recommend automatic reporting of estimated glomerular filtration rate (eGFR) using the abbreviated Modification of Diet in Renal Disease (MDRD) equation with every request for plasma creatinine. The Mayo Clinic Quadratic Equation (MCQE) has been put forwards as a potentially more accurate alternative. We therefore evaluated its accuracy compared with radionuclide GFR in a clinical setting. Method: Data were collected on 601 patients aged 16–85 years who had undergone radionuclide GFR, and eGFR was calculated using MCQE and MDRD. Calculations of bias, correlation coefficients and percentage estimates within 30% and 50% of radionuclide GFR were used in comparisons. Results: The MCQE had a significant positive bias in the overall population but no significant bias in individuals with normal renal function defined as measured GFR > 90 mL/min per 1.73 m². There was no significant difference in the performance of MCQE and MDRD eGFR in patients with measured GFR > 90 mL/min per 1.73 m². However, in the overall group and in subjects with radionuclide GFR < 90 mL/min per 1.73 m², the accuracy of MDRD eGFR with respect to the proportion of patients within 30% and 50% of radionuclide GFR was better than MCQE. Conclusion: MCQE compared moderately well with radionuclide GFR, although its overall bias and accuracy were inferior when compared with the MDRD equation in a clinical setting.     

Prevalence of Chronic Kidney Disease Is Extremely High in Heart Transplant Recipients

Patients with cardiovascular disease often have renal dysfunction from concomitant diabetes mellitus, hypertension, or congestive heart failure. Glomerular filtration rate (GFR) less than 60 mL/min is predictive of premature death due to cardiovascular disease. The objective of the present study was to assess the prevalence of kidney dysfunction in 162 heart transplant recipients using estimated GFR according to the Cockcroft-Gault and the simplified Modification of Diet in Renal Disease (MDRD) formulas or creatinine clearance (24-hour urine collection). Normal serum creatinine concentrations were noted in 46% of patients. Mean (SD) GFR was 62.92 (31.04) mL/min using the Cockcroft-Gault formula, 55.38 (26.74) mL/min using the MDRD formula, and 62.62 (35.61) mL/min according to creatinine clearance. Using the Cockcroft-Gault formula, a diagnosis of stage 2 chronic kidney disease (CKD) (GFR 60–89 mL/min) was made in 92 patients (56.8%), stage 3 (GFR 30–59 mL/min) in 62 patients (38.3%), and stage 4 (GFR 15–29 mL/min) in 14 patients (8.6%). Using the MDRD formula, stage 2 CKD was present in 52 patients (28.5%), stage 3 in 77 (51.1%), and stage 4 in 28 (17.3%). According to creatinine clearance, stage 2 CKD was noted in 10 patients (6.2%), stage 3 in 114 (73.3%), and stage 4 in 21 (13.0%). We conclude that the prevalence of CKD is extremely high in heart transplant recipients. Evaluation of renal function is important to select the appropriate technique to reduce cardiovascular risk. A multidisciplinary approach in heart transplant recipients should include a nephrologist.     

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.     

GFR prediction using the MDRD and Cockcroft and Gault equations in patients with end-stage renal disease.

BACKGROUND: Although prediction equations are recommended to determine GFR and creatinine clearance (CrCl), neither the MDRD equations nor the Cockcroft and Gault formula have been validated for the low levels of GFR present in end-stage renal disease (ESRD). The accuracy of the MDRD equations and the Cockcroft and Gault formula in predicting GFR and CrCl, respectively, was examined in patients with ESRD and its relationship to the basal GFR and two markers of malnutrition, urinary creatinine and body fat determined. METHODS: Inulin clearance (C(in)) was measured in 26 non-diabetic patients with ESRD and the 24 h CrCl determined. GFR was predicted using three equations derived from the MDRD study population containing four to six variables. Both CrCl and GFR were predicted from the Cockcroft and Gault formula. Estimates of bias and precision were obtained and Bland and Altman analysis performed. Body fat was measured by DEXA scan. RESULTS: The predicted GFR (MDRD) was 10% lower than C(in) (8.83+/-0.71 ml/min/1.73 m2) with all three MDRD equations, showing a similar degree of precision and bias. C(in) gave a negative correlation with the difference between the predicted GFR (MDRD) and the measured GFR. The predicted GFR (MDRD) underestimated GFR when C(in) >8 ml/min/1.73 m2 but overestimated GFR when C(in) <8 ml/min/1.73 m2. The Cockcroft and Gault formula overestimated CrCl by 14% and overestimated C(in) by 35%. C(in) gave a negative correlation with the difference between the predicted GFR (Cockcroft and Gault) and measured GFR, overestimating GFR when C(in) <13 ml/min/1.73 m2. The overestimation of GFR by the MDRD equation was not associated with urinary creatinine excretion. However, both Cockcroft and Gault and the MDRD predictions showed a positive, but weak, correlation with body fat. CONCLUSION: The MDRD equations were more accurate in predicting the group mean GFR in patients with ESRD than the Cockcroft and Gault formula. However, the predicted GFR using either formula was related to the basal GFR and percentage body fat.     

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.     

Is cystatin C useful for the detection and the estimation of low glomerular filtration rate in heart transplant patients?

Although previously studied in patients with chronic kidney disease, there is less data for the use of cystatin C and cystatin C-based formulas in heart transplant recipients. The ability of creatinine and cystatin C to detect renal failure (glomerular filtration rate [GFR] below 60 mL/min/1.73 m(2)) in heart transplant patients has been compared. The accuracy and precision of a creatinine-based formula (Modification of Diet in Renal Disease [MDRD]) versus a cystatin C-based formula (Rule's formula) to estimate GFR have also been studied. GFR was measured using the (51)Cr-ethylenediamine tetraacetic acid tracer in 27 patients. There was no significant difference between GFR and the reciprocal of creatinine or cystatin C. Receiver operating characteristic curves for cystatin C and creatinine were similar. Both formulas were well correlated with the GFR. The bias of the cystatin C-based was significantly better than one of the MDRD formula, but the standard deviation appeared better for the MDRD formula (bias of +3.9 mL/min/1.73 m(2) versus +12 mL/min/1.73 m(2) and SD of 8.5 versus 11.6, respectively). Plasma cystatin C has no clear advantage over serum creatinine to detect renal failure in heart transplanted patients.     

Comparison of 99mTc-DTPA renal dynamic imaging with modified MDRD equation for glomerular filtration rate estimation in Chinese patients in different stages of chronic kidney disease.

BACKGROUND: The renal dynamic imaging method (modified Gate's method) with (99m)Tc-diethylene triamine pentaacetic acid ((99m)Tc-DTPA) is simple and less time consuming for glomerular filtration rate (GFR) estimation than other methods. However, its diagnostic performance as a surrogate marker of GFR is questioned increasingly. Recently, the modified Modification of Diet in Renal Disease (MDRD) study equation based on data from Chinese patients of chronic kidney disease (CKD) showed significant performance improvement. In the present study, the renal dynamic imaging methods and the modified abbreviated MDRD equation were compared with the plasma clearance method. METHODS: Four hundred and eighty two patients with CKD were selected. GFR were estimated simultaneously using three methods: (i) modified Gate's method (gGFR); (ii) the modified abbreviated MDRD equation (c-aGFR) and (iii) dual plasma sampling method (rGFR). Using rGFR as the reference method, gGFR and c-aGFR were compared with rGFR in each stage of CKD. RESULTS: Both gGFR and c-aGFR were correlated well with rGFR (r(gGFR) = 0.81 and r(c-aGFR) = 0.90, P < 0.001). In the overall performance, c-aGFR had less bias (849.5 vs 933.1 arbitrary units), higher precision (57 vs 78.4 ml/min/1.73 m(2)) and higher accuracy than gGFR. For gGFR, the 15, 30 and 50% accuracies were 32.4, 56.0 and 79.1%, respectively; for c-aGFR, the corresponding accuracy rose to 43.2%, 75.5% and 90.9%, respectively. In each stage of CKD, the modified abbreviated MDRD equation also outperformed the modified Gate's method in the GFR estimation. CONCLUSION: Our results indicated that the performance of the renal dynamic imaging in total GFR estimation was not better than the modified abbreviated MDRD equation in our patient group, and should not be used as a surrogate marker of GFR, especially in clinical trials. We presume that the dynamic renal imaging methods for estimation of GFR can be improved by using proper reference GFR, more adequate background subtraction and soft-tissue attenuation correction, in a relatively larger sample size.     

Comparison of cross-sectional renal function measurements in African Americans with hypertensive nephrosclerosis and of primary formulas to estimate glomerular filtration rate

Renal function measurements were obtained in 1,703 African Americans with presumed hypertensive nephrosclerosis who were screened for entry into the African-American Study of Hypertension and Kidney Disease (AASK). We examined the effect of race on relationships involving renal variables by comparing African Americans enrolled into the AASK with non-African Americans enrolled into the Modification of Diet in Renal Disease (MDRD) study. We examined the effect of gender on renal variables by comparing African American men and women. We compared various methods for estimating glomerular filtration rate (GFR) with iodine 125-labeled (¹²⁵I)-iothalamate GFR. AASK data were also used to derive a new formula for estimating GFR in African Americans. After adjusting for age, sex, and baseline GFR, African American patients on the AASK study were heavier and had larger body surface areas and body mass indices than either MDRD African Americans or non-African Americans. African Americans had greater serum creatinine levels and urinary creatinine excretions for any given level of GFR. Mean GFR was greater in African American men than African American women (59.7 versus 51.7 mL/min/1.73 m²), although serum creatinine levels were also greater in men (1.91 versus 1.73 mg/dL). Seventy-eight percent of women with serum creatinine levels between 1.2 and 1.5 mg/dL had GFRs less than 65 mL/min/1.73 m². For African Americans in the AASK, GFR was overestimated by the 24-hour creatinine clearance and underestimated by the Cockcroft-Gault formula. A prediction formula developed in the MDRD study more accurately predicted GFR in AASK patients than these measurements. AASK data were also used to derive a new five-term formula for estimating GFR that was slightly more accurate in the African Americans in the AASK than the MDRD formula (median percentage of error, 12.4% for the MDRD formula versus 12.1% for the AASK formula). Important differences exist in renal variables between African Americans and non-African Americans and between African American men and African American women. Formulas using demographic data and readily measured serum values estimate ¹²⁵I-iothalamate GFR. © 2001 by the National Kidney Foundation, Inc.