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Journal Article 
A simplified equation to predict glomerular filtration rate from serum creatinine 
Levey, AS; Greene, T; Kusek, JW; Beck, GJ 
Journal of the American Society of Nephrology
ISSN: 1046-6673
EISSN: 1533-3450 
We recently developed and validated an equation 10 predicl GFR from serum creatinine (Pcr), which is more accurate than creatinine clearance measured from 24-hour urine samples or predicted from the Cockcroft-Gault (CG) equalion (Levey AS. Ann Intern Med 1999; 130:877-884). GFR is expressed as mI/min/1.73 m2. Required variables include Per (mg/dl), age (y), race (black vs. non-black), gender, serum urea nitrogen (SUN, mg/dl) and albumin (alb, g/dI). In clinical practice and in retrospective studies, measurements of SUN and alb may not be available. Below we list the full MDRD Study prediction equation (6 variables), as well as alternative prediction equations including fewer variables derived from measurements in the same 1628 patients.
GFR = 170 x Pcr-0.999 x age-0.176 x 1.180 (if black) x 0.762 (if female) x SUN-0.170 x alb+0.318
GFR = 270 x Pcr-1.007 x age-0.180 x 1.178 (if black) x 0.755 (if female) x SUN-0.169
GFR = 186 x Pcr-1.154 x age-0.203 x 1.212 (if black) x 0.742 (if female)

The table below compares the performance of these equations and the CG equation.
------------------ R ---- median delta -- 75th% delta -- 90th% delta
6 variables -- .903 -- 11.3% ---------- 19.8% --------- 28.4%
5 variables -- .899 -- 11.6% ---------- 19.9% --------- 29.4%
4 variables -- .892 -- 12.1% ---------- 20.5% --------- 29.7%
CG ------------ .842 -- 13.8% ---------- 26.4% --------- 40.5%
Delta = absolute value of the median (50th), 75th and 90th percentiles of the distribution of the differences between measured GFR and predicted GFR or Ccr for each equation (includes bias correction for CG equation).

We conclude that simplified versions of the MDRD Study prediction equation provide more accurate estimates of GFR than measured or estimated creatinine clearance. 
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