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.     

African ancestry, socioeconomic status, and kidney function in elderly African Americans: a genetic admixture analysis

Kidney disease is a major public health problem in the United States that affects African Americans disproportionately. The relative contribution of environmental and genetic factors to the increased burden of kidney disease among African Americans is unknown. The associations of genetic African ancestry and socioeconomic status with kidney function were studied cross-sectionally and longitudinally among 736 community-dwelling African Americans who were aged >65 yr and participating in the Cardiovascular Health Study. Genetic African ancestry was determined by genotyping 24 biallelic ancestry-informative markers and combining this information statistically to generate an estimate of ancestry for each individual. Kidney function was evaluated by cystatin C and estimated GFR (eGFR) using the Modification of Diet in Renal Disease equation. Longitudinal changes in serum creatinine and eGFR were estimated using baseline and follow-up values. In cross-sectional analyses, there was no association between genetic African ancestry and either measure of kidney function (P = 0.36 for cystatin C and 0.68 for eGFR). African ancestry was not associated with change in serum creatinine > or =0.05 mg/dl per yr (odds ratio [OR] 0.94; 95% confidence interval [CI] 0.83 to 1.06) or with change in eGFR > or =3 ml/min per 1.73 m(2) per yr (OR 1.02; 95% CI 0.92 to 1.13). In contrast, self reported African-American race was strongly associated with increased risk for kidney disease progression compared with white individuals for change in creatinine (OR 1.77; 95% CI 1.33 to 2.36) and for change in eGFR (OR 3.21; 95% CI 2.54 to 4.06). Among self-identified African Americans, low income (< US dollars 8000/yr) was strongly associated with prevalent kidney dysfunction by cystatin C >1.29 g/dl (adjusted OR 2.7; 95% CI 1.0 to 7.5) or by eGFR <60 ml/min per 1.73 m(2) (adjusted OR 3.2; 95% CI 1.1 to 9.4) compared with those with incomes >US dollars 35,000/yr. Alleles that are known to be present more frequently in the African ancestral group were not associated with kidney dysfunction or kidney disease progression. Rather, kidney dysfunction in elderly African Americans seems more attributable to differences in environmental and social factors.     

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.     

Predicting GFR in children and adults: a comparison of the Cockcroft-Gault,Schwartz, and modification of diet in renal disease formulas

BACKGROUND: A rapid prediction of glomerular filtration rate (GFR) is often needed in clinics. Formulas based on plasma creatinine level are being increasingly used, Schwartz for children, supposed to give GFR; Cockcroft-Gault for adults, supposed to indicate the creatinine clearance; and a recent formula introduced by the Modification of Diet in Renal Disease (MDRD) group. Our objective was to test whether one single formula could suffice and which one gives the best estimation of GFR. METHODS: In 198 children (with two kidneys, single kidney, or renal transplant) and 116 adults (single kidney and transplanted), we measured inulin clearance and creatinine clearance and calculated Cockcroft-Gault, MDRD and, in children only, Schwartz. Data were compared with analysis of variance (ANOVA), regression statistics, and concordance studies. RESULTS: In patients over 12 years of age, Cockcroft-Gault was almost similar to GFR corrected for body surface and creatinine clearance exceeded GFR by more than 20%; Schwartz was above creatinine clearance excepted for transplanted children. In younger children, no prediction approached GFR. Predictions were well correlated with GFR, but concordance studies showed Schwartz with dispersed results and GFR overestimated (20 mL/min/1.73 m2); Cockcroft-Gault was close to GFR and results were dispersed; MDRD in children gave a large overestimation and badly dispersed results; in transplanted adults its prediction was good. CONCLUSION: Cockcroft-Gault prediction could be used for children over 12 years of age and adults; it should not be considered as creatinine clearance but as GFR corrected for body surface, it is merely a prediction, 95% of the results are between +/-40 mL/min/1.73 m(2) in children and +/-30 mL/min/1.72 m(2) in adults. In younger children no formula is satisfying.     

Assessing Glomerular Filtration Rate by Estimation Equations in Kidney Transplant Recipients

Surveillance of glomerular filtration rate (GFR) is crucial in the management of kidney transplant recipients. With especial emphasis on serum creatinine (SCr) calibration assay, we assessed the performance of estimation equations as compared to iothalamate GFR (iGFR) in 209 patients using the modification of diet in renal disease (MDRD), Nankivell and Cockcroft-Gault methods. Fifty-five percent of patients were treated with a calcineurin inhibitor (CNI) and all were taken trimethroprim-sulfametoxazole at the time of SCr measurement. The mean iGFR was 44 ± 26 mL/min/1.73 m². The MDRD equation showed a median difference of 0.9 mL/min/1.73 m² with 53% of estimated GFR within 20% of iGFR. Median differences were 7.5 and 7.0 mL/min/1.73 m² for Nankivell and Cockcroft-Gault formulas, respectively. The accuracy of the Nankivell and Cockcroft-Gault formulas was such that only 38% and 37% of estimations, respectively, fell within 20% of iGFR. The performance of all equations was not uniform throughout the whole range of GFR, with some deterioration at the extremes of GFR levels. In addition, good performance of the MDRD equation was seen in subjects taking CNI. In conclusion, the overall performance of the MDRD equation was superior to the Nankivell and Cockcroft-Gault formulas in renal transplant recipients including subjects treated with CNI.     

Evaluation of the modification of diet in renal disease study equation in a large diverse population

Glomerular filtration rate (GFR) estimates facilitate detection of chronic kidney disease. Performance of the Modification of Diet in Renal Disease (MDRD) Study equation varies substantially among populations. To describe the performance of the equation in a large, diverse population, estimated GFR (eGFR) was compared to measured GFR (mGFR) in a cross-sectional analysis of 5504 participants in 10 studies that included measurements of standardized serum creatinine and urinary clearance of iothalamate. At eGFR <60 ml/min per 1.73 m(2), the MDRD Study equation had lower bias and higher precision than at eGFR > or =60 ml/min per 1.73 m(2). The accuracy of the equation, measured by the percent of estimates that fell within 30% of mGFR, was similar for eGFR values above or below 60 ml/min per 1.73 m(2) (82% and 84%, respectively). Differences in performance among subgroups defined by age, sex, race, diabetes, transplant status, and body mass index were small when eGFR was <60 ml/min per 1.73 m(2). The MDRD Study equation therefore provides unbiased and reasonably accurate estimates across a wide range of subgroups when eGFR is <60 ml/min per 1.73 m(2). In individual patients, interpretation of GFR estimates near 60 ml/min per 1.73 m(2) should be interpreted with caution to avoid misclassification of chronic kidney disease in the context of the clinical setting.     

Estimating the prevalence of renal insufficiency in seniors requiring long-term care

BACKGROUND: Renal function declines with age, but little is known about the extent of renal insufficiency among the institutionalized elderly. The objective of this study was to estimate the prevalence of low glomerular filtration rate (GFR) in a large sample of elderly adults living in long-term care facilities, and to compare two commonly used methods for estimating GFR. METHODS: A total of 9931 residents aged 65 years and older participated in a retrospective cross-sectional study of 87 long-term care facilities in Ontario. GFR was estimated by the Cockcroft-Gault and Modification of Diet in Renal Disease Study (MDRD) equations. The prevalence of low GFR, using the Cockcroft-Gault equation (<30 mL/min), was compared with the MDRD equation (<30 mL/min/1.73 m2). RESULTS: A total of 17.0% (95% CI 15.6 to 18.5) of men and 14.4% (95% CI 13.6 to 15.3) of women had a serum creatinine concentration above the laboratory reported upper reference limit of normal. The prevalence of both elevated serum creatinine and low GFR were observed to increase with age (P < 0.0001). The Cockcroft-Gault equation produced a consistently lower estimate of GFR than did the MDRD equation, a discrepancy most pronounced in the oldest residents. Among all men, a low GFR was more prevalent using the Cockcroft-Gault (10.3%, 95% CI 9.2 to 11.5) than MDRD (3.5%, 95% CI 2.8 to 4.2) equation, with a similar difference also seen in women (23.3%, 95% CI 22.4 to 24.3 versus 4.0%, 95% CI 3.6 to 4.5, respectively). Of all residents whose Cockcroft-Gault estimated GFR was under 30 mL/min, 14.7% (95% CI 13.2 to 16.3) were found to have GFR greater than 60 mL/min/1.73 m2 according to the MDRD equation. CONCLUSION: Age-associated renal impairment is common among elderly long-term care residents, but there exists a clear discrepancy between the Cockcroft-Gault and MDRD equations in predicting GFR. Consideration should be given to medication dose adjustment, based on a practical estimate of GFR. However clarification is needed about which method, if either, is most valid among the frail elderly. Complex patient and societal issues surrounding advanced care directives, treatments associated with renal insufficiency, and, if and when to initiate dialysis, require further attention.     

Prevalence of chronic kidney disease based on estimated glomerular filtration rate and proteinuria in Icelandic adults.

BACKGROUND: The purpose of this study was to compare three different equations to calculate estimated glomerular filtration rate (eGFR) based on serum creatinine (SCr) and to estimate the prevalence of chronic kidney disease (CKD) in the Icelandic population. METHODS: This was a cross-sectional study using data from the Reykjavik Heart Study. GFR was estimated with three equations: Equation I was based on 1/SCr; Equation II based on the Cockcroft-Gault equation; and Equation III was the modified MDRD equation. The eGFR calculated with Equation III and proteinuria were used to estimate the prevalence of CKD. The prevalence was age-standardized to the truncated world population. We used chi-square and ANCOVA to compare the group with low eGFR to age-matched controls. RESULTS: The subjects consisted of 9229 males and 10,027 females, aged 33-85 years. The equations performed very differently. Equation I showed women with higher eGFR than men and little change with age. Equation II showed men with higher eGFR than women and marked decline in eGFR with age. Equation III was similar to Equation II but the decline in eGFR with age was not as great. Regardless of the equation used, most subjects (63.7-80.7%) had an eGFR in the range of 60-89 ml/min/1.73 m2. Using Equation III, age-standardized prevalence of low eGFR for the population aged 35-80+ years was estimated to be 4.7 and 11.6% for men and women, respectively. The proportion of subjects with eGFR <60 ml/min/1.73 m2 increased with advancing age. An additional 2.39% of men and 0.89% of women had proteinuria. The prevalence of renal and cardiovascular risk factors including proteinuria, hypertension, lipid abnormalities and markers of inflammation was higher among those with low eGFR than age-matched controls. CONCLUSIONS: GFR estimates and the prevalence of CKD are dependent on the equation used to calculate eGFR. Unexpectedly, a low proportion of the Icelandic population had normal kidney function according to the eGFR regardless of the equation used. These equations may not be useful in epidemiological research.     

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.     

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 association of serum lipids and inflammatory biomarkers with renal function in men with type II diabetes mellitus

Dyslipidemia and inflammation may promote renal disease via mechanisms of vascular endothelial cell dysfunction in type II diabetes mellitus (DM). Sparse data, however, are available on the relation of lipids and inflammatory biomarkers and glomerular filtration rate (GFR) in type II DM. We performed a cross-sectional study of 732 men with type II DM enrolled in the Health Professionals' Follow-Up Study. Plasma creatinine was used to estimate GFR by the simplified Modification of Diet in Renal Disease (MDRD) equation. In men with a GFR <60 ml/min/1.73 m(2), triglycerides, non-high-density lipoprotein (HDL), apoprotein B, fibrinogen, soluble tumor necrosis factor receptor (sTNFR-2) and vascular cell adhesion molecule-1 (VCAM) were significantly higher when compared to the referent group (GFR> or =90 ml/min/1.73 m(2)). In multivariable logistic regression, those in the highest quartiles of the following biomarkers had increased odds of having a GFR <60 ml/min/1.73 m(2) when compared to those in the lowest quartiles: triglycerides (odds ratio (OR) 3.11; 95% CI, 1.52-6.36), fibrinogen (OR 5.40; 95% CI 2.14-13.65), sTNFR-2 (OR 8.34; 95% CI 3.50-19.88) and VCAM (OR 4.50; 95% CI 1.98-10.23). An inverse association was observed for HDL (OR 0.48; 95% CI 0.24-0.98). We found no association between C-reactive protein and GFR. The results were similar when creatinine clearance by Cockcroft-Gault was used to estimate kidney function. We conclude that several potentially modifiable lipid and inflammatory biomarkers are elevated in the setting of moderately decreased GFR in men with type II DM and may be the link between renal insufficiency and increased risk for cardiovascular events in this population.     

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.     

Evaluation and applicability of predictive equations of the glomerular filtration rate in chronic kidney disease

Prediction equations of glomerular filtration rate (GFR) may facilitate early detection, evaluation and management of chronic kidney disease (CKD). However, the reliability of these equations was not extensively studied in our CKD population. Hence, the present study was aimed to determine the performance of modification of diet in renal disease (MDRD) and Cock-croft Gault formulas in predicting GFR in CKD patients and their relationship with the measured GFR. A total of 104 subjects (71 male and 33 female, aged 26-68 years) with different stages of CKD were recruited for this study; we excluded 51 patients due to improper collection of 24-h urine. The GFR was measured using 24-h creatinine clearance and predicted by the Cockcroft Gault, the 4-variable MDRD and the 6-variable MDRD equations. Prediction equations correlated well with the measured GFR. However, the predicted GFR using the 4-variable MDRD equation revealed a highly significant positive correlation with the GFR measured by creatinine clearance (r = 0.86, P < 0.001), followed by the 6-variable MDRD and Cockcroft-Gault equations with r = 0.85 and 0.77, P < 0.001, respectively. In conclusion, the present study predicts that the 4-variable MDRD is the best available equation for predicting GFR in our CKD population.     

Validation of creatinine-based estimates of GFR when evaluating risk factors in longitudinal studies of kidney disease

Whereas much research has investigated equations for obtaining estimated GFR (eGFR) from serum creatinine in cross-sectional settings, little attention has been given to validating these equations as outcomes in longitudinal studies of chronic kidney disease. A common objective of chronic kidney disease studies is to identify risk factors for progression, characterized by slope (rate of change over time) or time to event (time until a designated decline in kidney function or ESRD). The relationships of 35 baseline factors with eGFR-based outcomes were compared with the relationships of the same factors with iothalamate GFR (iGFR)-based outcomes in the African American Study of Kidney Disease and Hypertension (AASK; n = 1094). With the use of the AASK equation to calculate eGFR, results were compared between time to halving of eGFR or ESRD and time to halving of iGFR or ESRD (with effect sizes expressed per 1 SD) and between eGFR and iGFR slopes starting 3 mo after randomization. The effects of the baseline factors were similar between the eGFR- and iGFR-based time-to-event outcomes (Pearson R = 0.99, concordance R = 0.98). Small but statistically significant differences (P < 0.05, without adjustment for multiple analyses) were observed for seven of the 35 factors. Agreement between eGFR and iGFR was somewhat weaker, although still relatively high for slope-based outcomes (Pearson R = 0.93, concordance R = 0.92). Effects of covariate adjustment for age, gender, baseline GFR, and urine proteinuria also were similar between the eGFR and iGFR outcomes. Sensitivity analyses including death in the composite time-to-event outcomes or using the Modification of Diet in Renal Disease equation instead of the AASK equation provided similar results. In conclusion, the data from the AASK provide tentative support for use of outcomes that are based on an established eGFR formula using serum creatinine as a surrogate for measured iGFR-based outcomes in analyses of risk factors for the progression of kidney disease.     

Association between decreased kidney function and endotoxin receptor CD14 C-159T polymorphism among Japanese health check-up examinees

BACKGROUND: A recently identified promoter polymorphism of the endotoxin receptor (CD14 C-159T) was shown to be associated with atherosclerotic diseases such as myocardial infarction. This study was conducted to determine whether this polymorphism is associated with decreased kidney function. METHODS: A total of 281 male and 522 female health check-up examinees, aged 39-88 years, were genotyped for CD14 C-159T. The glomerular filtration rate (GFR) was estimated by the Modification of Diet in Renal Disease (MDRD) Study equation. Estimated GFR (eGFR) and the proportion of subjects with mildly decreased eGFR (eGFR under 90 mL/min/1.73 m(2)) were compared among the genotypes. RESULTS: Subjects carrying the T allele showed decreased age- and sex-adjusted eGFR compared with those with CC genotype (101+/-22 vs. 105+/-23 mL/min/1.73 m(2); mean+/-SD, p = 0.012). The proportion of subjects with mildly decreased eGFR was higher in T allele carriers (34.2% for TT+CT and 26.3% for CC genotype, p = 0.041), but not statistically significant when adjusted for age and sex (odds ratio [OR] 1.41, 95% CI 0.97-2.05, p = 0.076). In subjects under 65 years, T allele carriers had a significantly increased risk for mildly decreased eGFR (27.1% for TT+CT and 18.0% for CC; age- and sex-adjusted OR 1.82, 95% CI 1.06-3.12, p = 0.030). CONCLUSION: CD14-159T allele was associated with decreased eGFR compared with CC genotype, and with a higher prevalence of mildly decreased eGFR in younger subjects under 65.     

MDRD-estimated GFR at one year post-renal transplant is a predictor of long-term graft function

Renal transplantation is the optimal mode of renal replacement. Improvements in graft survival and acute rejection rates have made these outcomes less useful for prognostication and as end-points in clinical trials; accurate surrogate markers of long-term graft outcome are therefore increasingly important. This study examines the relationship between both serum creatinine (SCr(1 yr)) and MDRD estimated glomerular filtration rate measured at one year (eGFR(MDRD)(1 yr)) as predictors of graft survival. Data on 1,110 patients who received a renal transplant between 1989 and 2005 were extracted from the Irish Renal Transplant Registry. The study group was divided into quartiles of patient numbers according to SCr(1 yr) and eGFR(MDRD)(1 yr). Kaplan-Meier estimates of the primary end-point graft survival were constructed for each quartile. Additionally, a Cox Regression restricted cubic spline model was performed for both eGFR(MDRD)(1 yr) and SCr(1 yr). Both overall graft outcome and outcome censored for death with a functioning graft (CDWFG) were used as endpoints. Cox regression analysis was performed along with tests for the proportionality assumption to compare the predictive value of eGFR(MDRD)(1 yr)and SCr(1 yr). Both eGFR(MDRD)(1yr) and SCr(1 yr) were independently associated with long-term renal transplant survival. eGFR(MDRD)(1 yr) and SCr(1 yr) had similarly strong associations with long-term outcome when the quartile variables were compared using the Bayesian Information Criterion method. The Cox regression restricted cubic spline modeling demonstrated that an eGFR(MDRD)(1 yr) value < 27 mLs/min/1.73 m(2) and a SCr(1 yr) value > 229 micromol/L were associated with poor graft survival.     

Understanding estimated glomerular filtration rate: implications for identifying chronic kidney disease

PURPOSE OF REVIEW: Glomerular filtration rate (GFR) can be estimated using serum markers such as serum creatinine (SCr) or cystatin C. This review presents new insights into estimated GFR based on theory, validation studies, SCr assay standardization, cystatin C, and longitudinal comparison with measured GFR. RECENT FINDINGS: The estimation of GFR by SCr differs in health and in chronic kidney disease (CKD) due to differences in GFR range and in creatinine production between these two populations. Among populations with normal baseline GFR, there is a more rapid decline in measured GFR than in SCr-based estimated GFR. While elevated SCr is specific for CKD, other disease processes may lead to elevated cystatin C. Validation is improved by refitting equation coefficients to compare populations, recognizing the asymmetry between estimated GFR and measured GFR, and using residual plots instead of Bland-Altman plots to assess bias. SUMMARY: As a screening test, SCr should be interpreted as a marker of CKD probability in the context of the patient's clinical presentation. Measured GFR or creatinine clearance may be helpful in high-risk patients with normal SCr levels. GFR estimating equations should be reserved for patients with identified CKD. Standardized SCr and cystatin C assays are needed.     

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.     

Comparison of different equations for estimated glomerular filtration rate in patients with chronic kidney disease

Objective To compare different equations for estimated glomerular filtration rate (eGFR) in patients with chronic kidney disease (CKD). Methods Hospitalized patients with CKD from the nephrology department of the First Affiliated Hospital of Nanjing Medical University (Jiangsu Province Hospital) were recruited between December 2014 and May 2015. The calculations of eGFR and 24 h creatinine clearance rate (Ccr) were accomplished in three days after admission. The eGFRs were calculated separately using the 24 h creatinine clearance rate adjusted by the standard body surface area (Ccr_BSA), Cockcroft-Gault equation adjusted by the standard body surface area (eCcr_BSA), CKD-EPI creatinine equation (EPI_Cr), CKD-EPI cystatin C equation (EPI_CysC), CKD-EPI creatinine-cystatin C equation (EPI_Cr_CysC), simplified MDRD (MDRD) and China MDRD equations. The EPI_Cr_CysC equation was used as the standard and the precision and accuracy of the other six equations were compared and analyzed. Results A total of 403 CKD participants were enrolled in the study, with 228 male patients and a mean age of (54.9±18.4) years. The main primary diseases were chronic glomerulonephritis (43.7%) and diabetic nephropathy (13.2%). The median concentration of serum creatinine and cystatin C were 117.5 (69.7, 242.4) μmol/L and 1.80 (1.13, 3.31) mg/L, respectively. The median values of Ccr_BSA, eCcr_BSA, MDRD, China MDRD, EPI_Cr, EPI_CysC and EPI_Cr_CysC equations were 50.8 (21.1, 96.2), 51.9 (23.3, 93.2), 53.6 (23.0, 97.4), 52.2 (22.4, 94.1), 53.2 (22.1, 97.3), 35.1 (15.4, 67.0) and 49.1 (22.8, 82.3) ml?min-1?(1.73 m2)-1, respectively. There was well agreement among MDRD, China MDRD and EPI_Cr equations, while there were large differences between equations derived from CysC (EPI_Cr_CysC and EPI_CysC) and equations derived only from creatinine (EPI_Cr, MDRD, China MDRD, eCcr_BSA, Ccr_BSA equations). Compared with EPI_Cr_CysC equation (the reference equation), EPI_Cr equation showed the highest accuracy [percentage of other eGFR equation calculations that were ＞30% of the reference equation calculations (1-P30), 30.8%] while Ccr_BSA equation showed the lowest (1-P30, 42.4%). EPI_CysC equation showed the highest precision [inter-quartile range (IQR) of the difference, 11.7 ml?min-1?(1.73 m2)-1] while Ccr_BSA equation showed the lowest [IQR of the difference, 22.8 ml?min-1?(1.73 m2)-1]. Conclusions The agreement among equations derived only from creatinine is better; while it exhibits some differences between equations with cystatin C and equations derived only from creatinine. The accuracy of EPI_Cr equation is second only to EPI_Cr_CysC equation and it is currently the most suitable eGFR equation for clinical popularization of renal glomerular function assessment.     

Kidney dimensions at sonography are correlated with glomerular filtration rate in renal transplant recipients and in kidney donors

The gold standard to assess renal function is the measurement of glomerular filtration rate (GFR). For practical reasons, renal function is often evaluated from serum creatinine (S Cr) or cystatin C (S Cys), and GFR is predicted from SCr. Ultrasound scanning of the kidneys is used only to evaluate renal morphology. The aim of this study was to evaluate the relationship between sonographic renal dimensions and GFR in renal transplant recipients and in kidney donors. GFR (urinary clearance of (99m)Tc-DTPA), S Cr, and S Cys were measured in 33 donors (28 females [F], 5 males [M]; SCr, 0.81-1.90 mg/dL) and 30 recipients (8 F, 22 M; SCr, 0.96-2.42 mg/dL). GFR was also predicted using the Cockcroft and Gault (CG) formula and with the simplified Modification of Diet in Renal Disease (MDRD) formula. Length, width, and depth of kidneys and renal sinus were measured using renal sonography. Among sonographic measurements, kidney length showed the best correlation with GFR. A closer correlation with GFR was found in donors (r = 0.639; P < .00007) than in recipients (r = 0.511; P < .005). In either case, the correlation of kidney length with GFR was greater than that of S Cr or S Cys, and similar to that of CG or MDRD GFR. Accuracy of kidney length as an indicator of GFR impairment was not statistically different from laboratory tests. Only in donors did CG show better accuracy. In conclusion, renal dimensions at sonography closely correlated with GFR. Thus, renal sonography can give information also on the function of the renal graft and of the remaining kidney of living donors.