Development of formulae for accurate measurement of the glomerular filtration rate by renal dynamic imaging.
OBJECTIVE
Currently, the widely adopted renal dynamic imaging in clinical practice uses Gates' method to calculate the glomerular filtration rate (GFR), but many researchers have proven that Gates' method may result in bias. Thus, this article explores alternative improved formulae to calculate GFR by renal dynamic imaging.


METHODS
Three hundred and sixty-seven patients were selected and their GFR values were measured using renal dynamic imaging and the two-plasma method with 99mTc-diethylenetriaminepentaacetic acid (99mTc-DTPA) as the imaging agent. With the two-plasma GFR as reference value, two equations were obtained from linear and non-linear regression analyses between the renal uptake percentage and two-plasma GFR. The 367 patients were divided into two random groups, with the first group used to derive the regression formulae and the second to verify the formulae. Finally, all patients were studied to derive the formulae to calculate GFR. The comparison of our formulae with the commonly used Gates' formula was conducted by the Bland-Altman method.


RESULTS
The linear and non-linear GFR formulae were as follows: GFR (ml/min/1.73 m2)=(631.633 x renal uptake percentage - 2.040) x 1.73/BSA (BSA, body surface area) and GFR (ml/min/1.73 m2)=(-1996.585 x renal uptake percentage2 + 1013.526 x renal uptake percentage - 12.739) x 1.73/BSA, respectively. The biases of the GFR values calculated using the linear and non-linear formulae and Gates' formula relative to the two-plasma GFR were -2.5 +/- 19.1 ml/min/1.73 m2, -2.0 +/- 19.3 ml/min/1.73 m2 and 3.4 +/- 19.4 ml/min/1.73 m2, respectively.


CONCLUSIONS
The GFR values calculated using our new formulae correlate better with the reference GFR value than does GFR calculated by Gates' formula, and the GFR values measured using the non-linear formula are more accurate than those obtained using the linear formula.
Li
Qian
Q
Department of Nuclear Medicine, Peking University First Hospital, Beijing, China. gurguer@163.com
Zhang
Chun-Li
CL
Fu
Zhan-Li
ZL
Wang
Rong-Fu
RF
Ma
Ying-Chun
YC
Zuo
Li
L
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007674:Kidney Diseases / Q000175:diagnosis* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011866:Radioisotope Renography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016284:Technetium Tc 99m Pentetate / Q000493:pharmacokinetics
D019275:Radiopharmaceuticals; D016284:Technetium Tc 99m Pentetate