A comparison between estimates of GFR using [99mTc]DTPA clearance and the approximation of Cockcroft and Gault.
BACKGROUND
The formula of Cockcroft and Gault, relating age, weight, sex and plasma creatinine is widely used to estimate glomerular function. Its ability to predict [99mTc]DTPA clearance, an accepted measure of GFR, is therefore of interest.


OBJECTIVE
To test prospectively the reliability of the formula in predicting the [99mTc]DTPA clearance in subjects with normal and sub-normal renal function.


METHODS
The 24 hour creatinine clearance (Ccr), the derived clearance using the formula (Cder), and the [99mTc]TPA clearance have been compared in 47 male and 47 female subjects, aged between 15 and 71 years. Obese and non-obese subjects (males > 90 kg, females > 80 kg body weight) were considered separately.


RESULTS
Across the range of [99mTc]DTPA clearance studied (14 to 125 mL/minute), in non-obese subjects, both Ccr and Cder were correlated similarly with [99mTc]DTPA clearance in males and females. In obese subjects as a group, Cder was also closely correlated with [99mTc]DTPA clearance but the scatter of data was wider. Among non-obese subjects, correlations were high between either Ccr or Cder and [99mTc]DTPA clearance values < 101 mL/minute but were not significant at [99mTc]DTPA clearance values > 100 mL/minute. For [99mTc]DTPA clearance values between 14 and 100 mL/minute, Cder was a more direct and more precise predictor of [99mTc]DTPA clearance [DTPA clearance = 1.01 (Cder) + 2.34, with 95% confidence limits of +/- 18 mL/minute] than of Ccr [Ccr = 1.34(CderC)-10.86, confidence limits +/- 28 mL/minute].


CONCLUSIONS
For very mild through to moderate renal failure, the formula of Cockcroft and Gault can evidently be used as a reasonable estimate of GFR.
Cochran
M
M
Department of Medicine, Flinders Medical Centre, Adelaide, SA.
St John
A
A
D000293:Adolescent; D000328:Adult; D000368:Aged; D003404:Creatinine / Q000097:blood / Q000378:metabolism*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007677:Kidney Function Tests / Q000379:methods; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012044:Regression Analysis; D051437:Renal Insufficiency / Q000175:diagnosis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016284:Technetium Tc 99m Pentetate
D003404:Creatinine; D016284:Technetium Tc 99m Pentetate