What is the most appropriate formula to use in estimating glomerular filtration rate in adult Arabs without kidney disease?
BACKGROUND
In clinical practice, the glomerular filtration rate (GFR) is often estimated by the Modification of Diet in Renal Disease (MDRD) or Cockcroft-Gault (CG) formulae. No data are available, however, on the performance of these formulae in Arab individuals.


METHODS
Plasma creatinine samples were obtained from 90 consecutive normal Arab kidney donors for the estimation of GFR (eGFR) using the simplified MDRD and CG formulae. The GFR was measured in these donors with chromium labelled EDTA {[51Cr] EDTA). Bias was assessed by calculating the difference between the measured GFR and the calculated GFR using each of the two formulae; precision was calculated using the r value of the regression analysis.


RESULTS
The group studied consisted of 90 donors, of whom 64 were males (71%). The mean age was 30.8 years (+/- 9.8) and mean BMI was 25.7 (+/- 5.7). The measured GFR (mean 112.4 +/- 17.5) correlated better with the calculated GFR by CG formula (mean 107.7 +/- 29.7) and showed poor correlation with the GFR estimated by the MDRD (mean 89.2 +/- 13.8); bias = 4.8 and 23.3, respectively (p = 0.1 and < 0.0001, respectively). The correlation with CG formula was better in males (bias = 2, p = 0.5) and those under 30 years of age (bias = 1.0, p = 0.9). Based on our data, we calculated a correction factor to the CG formula to improve the correlation with the measured GFR in Arab individuals. By multiplying the CG formula by 1.0446, the bias was reduced from 4.8 (p = 0.1) to 0.0 (p = 0.5) with an increase in precision from 0.2 (p = 0.05) to 0.43 (p = 0.0001). Using CG formula, the frequency for values within 30% of the mean of the measured value was 75%, which improved to 80% using the revised formula.


CONCLUSIONS
CG formula was found to be the most appropriate for calculation of GFR in Arab individuals. It is possible to reduce the bias and improve precision in Arab individuals with normal renal function by multiplying the result obtained by CG formula by 1.0446.
Al-Khader
Abdulla A
AA
King Saud bin Abdulaziz University for Health Sciences and King Abdulaziz Medical City, Riyadh, Saudi Arabia.
Tamim
Hani
H
Sulaiman
Mohamed Hamad Al
MH
Jondeby
Mohamed Shami
MS
Taher
Saadi
S
Hejaili
Fayez Faleh
FF
Ghamdi
Ghormullah
G
Flaiw
Ahmed
A
Hakami
Ali
A
D000328:Adult; D003404:Creatinine / Q000097:blood*; D003430:Cross-Sectional Studies; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007674:Kidney Diseases / Q000097:blood / Q000175:diagnosis / Q000208:ethnology; D007677:Kidney Function Tests / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012529:Saudi Arabia / Q000453:epidemiology; D012680:Sensitivity and Specificity; D014019:Tissue Donors / Q000706:statistics & numerical data*
D003404:Creatinine