MDRD formula

MDRD Formula for Estimating Glomerular Filtration Rate (from the Modification of Diet in Renal Disease Study)3... 

There is growing popularity of the formulae used to predict eGFR. While Cockcroft/Gault is the oldest, the MDRD formulae has gained greater use since it is most useful at GFR < 60 ml/min/1.73m [111]. How reliable these values are with rapidly changing serum creatinine values is problematic. 

Calculated Clearance. The mathematical relationship between plasma creatinine and GFR can be improved by correcting for the confounding variables that make that relationship nordinear. More than 25 different formulas have been derived that estimate GFR using plasma creatinine corrected for some or all of gender, body size, race, and age. These may produce a better estimate of GFR than serum creatinine alone. Indeed the National Kidney Foundation of the United States has recommended that such estimates should be used in preference to serum creatinine, and that either the Cockcroft and Gault or Modification of Diet in Renal Disease (MDRD) formula should be used in adults. The Schwartz and Counahan-Barratt formulas are recommended for use in children. 

They observed that the MDRD equation provided more accurate assessment of GFR than either the Cockcroft and Gault equation or measured creatinine clearance. The MDRD formula has several advantages (1) it was developed and validated in a large population, (2) it was developed with a population that included both European-Americans and African-Americans, (3) it does not require patient weight, (4) it was validated against an iothalamate clearance estimate... 

Plasma creatinine is an imperfect marker of GFR and therefore it is not altogether surprising that formulas based predommantly upon it are imperfect. Their use cannot circumvent the very significant spectral interferences affecting plasma creatinine measurement (i.e., hemolysis, icterus, and lipemia) and the formulas are unsuitable for use in patients with acute renal failure, in whom plasma creatinine concentrations are changing rapidly. Additionally, the formulas are critically susceptible to variations in creatinine assay calibration and specificity. Notwithstanding the MDRD formula is thought to improve the estimation of GFR compared with plasma creatinine alone. 

Harmoinen A, Lehtimaki T, Korpela M, Turjanmaa V, Saha H. Diagnostic accuracies of plasma creatinine, cystatin C, and glomerular filtration rate calculated by the Cockcroft-Gault and Levey (MDRD) formulas. Clin Chem 2003 49 1223-5. 

The assessment of kidney function with estimated glomerular filtration rate (eGFR) using CKD-Epidemiology Collaboration (CKD-EPI) and Modification of Diet in Renal Disease (MDRD) formulas is key for correct and safe drug prescribing. 

Total drug clearance is the sum of nonrenal clearance and renal clearance (Clren). According to the MDRD-2 formula, the estimated GFR (eGFR) is a function of serum creatinine (SCr in mg/dl) and age (Age in years). It has the unit ml/min per 1.73 mA2. 

The effect of hemofiltration on drug elimination can be estimated from serum creatinine (SCr), age, and the MDRD-2 formula to predict the combined effect of filtration rate (eGFR = GFRresidual + HFR) on drug clearance and drug half-life during hemofiltration. 

Calculate Mr WD s renal function using the MDRD equation and the Cockcroft-Gault formula. 

An alternative to the measurement of the Ccr is the use of either nomograms or formulae to estimate the glomerular filtration rate. The two most widely used equations are the Cockcroft-Cault and the Modifica-hon of Diet in Renal Disease (MDRD) study equations [46,47]. 

In practice, there may be little to choose between the Cockcroft and Gault formula and the more recently described MDRD equation,and which is chosen will be... 

In general, there is a wide degree of scatter when values of glomerular filtration rate are predicted by these equations, although the equation derived from the MDRD study provides more accurate estimates of GFR than the other formulae or measured clearances... 

Table 1. List of the most common formulas for eGFR used for guiding drug dosage adjustment (see www.mdrd.com)...

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