Estimation of glomerular filtration rate in older patients with chronic renal insufficiency: is the modification of diet in renal disease formula an improvement?
OBJECTIVE
To evaluate a new formula for glomerular filtration rate (GFR), derived from the Modification of Diet in Renal Disease (MDRD) study in older people.


METHODS
An observational study of the performance of the MDRD formula compared with other formulae and creatinine clearance (ClCr) as measures of the GFR.


METHODS
Volunteers were recruited via outpatient clinics.


METHODS
Fifty-two patients (27 men, 25 women: mean age 80, range 69-92) with a variety of medical diagnoses. Mean GFR was 53.3 mL/min/1.73 m2 (range 15.9-100.2). Exclusion criteria included renal replacement therapy/renal transplantation and cognitive impairment.


METHODS
51Chromium ethylenediaminetetraacetic acid (51Cr EDTA) was used as the reference method against which the formulaic estimates of GFR were compared using bias plot and regression analyses.


RESULTS
The MDRD and Cockcroft and Gault formulae (both coefficient of determination (R2) = 0.84) gave the best fit with GFR, followed by the Jelliffe formula (R2 = 0.81), ClCr (R2 = 0.73) and the Baracskay formula (R2 = 0.56). ClCr (-1.2%) demonstrated minimal bias compared with the MDRD (8.0%) and Cockcroft and Gault (-10.4%) formulae. However, imprecision compared with 51Cr EDTA was lowest for the Cockcroft and Gault formula, with 50% of estimates lying between -9.5 and -0.5 mL/min/1.73 m2 of measured 51Cr EDTA clearance. This compares with -6.7 and 10.1 mL/min/1.73 m2 for ClCr and 0.0 and 12.7 mL/min/1.73 m2 for the MDRD formula.


CONCLUSIONS
Calculated estimates of GFR are an improvement over ClCr estimation. On balance, the MDRD formula does not improve the estimate of GFR compared with the Cockcroft and Gault formula in older Caucasian patients with chronic renal insufficiency.
Lamb
Edmund J
EJ
Department of Clinical Biochemistry, East Kent Hospitals NHS Trust, Kent and Canterbury Hospital, Canterbury, Kent, United Kingdom. edmund.lamb@ekht.nhs.uk
Webb
Michelle C
MC
Simpson
David E
DE
Coakley
Anthony J
AJ
Newman
David J
DJ
O'Riordan
Shelagh E
SE
D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015982:Bias; D003404:Creatinine / Q000097:blood; D005247:Feeding Behavior / Q000502:physiology*; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood / Q000175:diagnosis* / Q000503:physiopathology*; D008297:Male; D008432:Mathematical Computing; D012044:Regression Analysis; D015203:Reproducibility of Results; D013223:Statistics as Topic / Q000379:methods*
D003404:Creatinine