Modification Of Diet In Renal Disease Study Equation Research Articles

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

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. 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. 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. 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.

Prevalence of chronic kidney disease and anemia among participants in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) Cohort Study: Baseline results

Prevalence of chronic kidney disease and anemia among participants in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) Cohort Study: Baseline results

Serum Creatinine as Marker of Kidney Function in South Asians

Migrant populations of South Asian origin have a higher risk for chronic kidney disease than the native whites. Several formulas have been developed to estimate kidney function from serum creatinine concentration. However, none of these has been validated in the South Asian population, which generally has different muscle mass composition than whites. A population-based cross-sectional study was performed on 262 individuals who were aged > or = 40 yr in Karachi, Pakistan. Reduced GFR was defined as creatinine clearance (Ccr) measured in 24-h urine collection of <60 ml/min per 1.73 m2. Creatinine excretion was compared with age- and gender-matched white individuals by comparison of observed versus expected results on the basis of a formula using t test. The agreement among Cockcroft Gault (CG) Ccr and Modification of Diet in Renal Disease (MDRD) Study GFR equations was assessed by regression analyses, and the degree of accuracy of estimated versus measured GFR was determined. Mean (95% confidence interval) creatinine excretion was 1.7 (1.0 to 2.4) mg/kg per d lower than expected for age- and gender-matched white individuals (P < 0.001). The coefficient of determination for measured Ccr on the logarithmic scale was 66.7 and 55.6% for the CG and MDRD Study equations, respectively. The proportion of estimates within 20, 30, and 50% of measured Ccr values was 47.7 versus 32.8% (P < 0.001), 64.9 versus 49.6% (P < 0.001), and 79.4 versus 72.9 (P = 0.07) for CG versus MDRD Study equations, respectively. Lower mean creatinine excretion in these individuals may explain, in part, suboptimal agreement between estimated versus measured GFR. Inclusion of terms for ethnic and racial groups other than white and black might improve the performance of GFR estimating equations.

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

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. 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). 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. 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.

Detection of impaired renal function

Summary Aim: Renal function is usually determined by means of creatinine-clearance, and of serum Cystatin C, the latter with increasing frequency. The present study analyses, whether the diagnostic accuracy of 99mTc-MAG3 clearance is comparable to that of these modern serologic methods. Patienten, Methods: 71 consecutive adult Caucasian patients (42 female, 29 male; age 50 ± 16 yrs., range 20 – 83) who were referred to a nuclear medicine department for determination of bilateral renal function with 99mTc-MAG3 were included. Following sufficient hydration, 10 ml of blood were taken for determination of Cystatin C and creatinine in serum prior to i.v. injection of the radiotracer. According to the recommendations of the National Kidney Foundation, glomerular filtration rate (GFR) was calculated from serum creatinine using either Cockcroft &amp; Gault and Modification of Diet in Renal Disease (MDRD) study equation. These estimates of GFR served as reference. Cystatin C is a low molecular protein produced by all nuclear cells and is eliminated to 85 % by glomerular filtration. Analysis of 99mTc-MAG3 clearance was performed by means of Bubeck’s formula. Results: Linear regression analysis produced Pearson’s correlation coefficients of r = 0.68 and r = -0.69 for the comparison of either Cystatin C and 99mTc-MAG3 clearance with the Cockcroft &amp; Gault equation. The comparison of Cystatin C and 99mTc-MAG3 clearance with MDRD study equation resulted in correlation coefficients of r = 0.755 and r = -0.77. None of these differences were significant. The exclusion of renal impairment or the detection of an at least moderate renal impairment revealed again no significant differences between Cystatin C and 99mTc-MAG3 clearance. Conclusions: Cystatin C and 99mTc-MAG3 clearance are equally suited to exclude renal impairment or to detect a relevant renal impairment. Differences between both procedures are more likely a result of the applied reference method.