1. Estimating Glomerular Filtration Rate In Overweight and Obese Malaysian Subjects
Nor-Hayati S1, Soehardy Z1, Norella Kong CT1, Rohana AG2, Nor-Azmi K2, Aini AA3 & Shamsul-Azhar S4
1Nephrology unit, 2Endocrinology unit, Department of Medicine; 3Department of Nuclear Medicine, 4Public Health Department;
Universiti Kebangsaan Malaysia

2. INTRODUCTION GFR is the best overall index of renal function1
Normal GFR varies with age, gender & body size
A decrease in GFR precedes the onset of kidney failure
GFR cannot be measured directly
Several equations for estimating GFR from Sr Cr & demographic characteristics have been developed2
GFR can be predicted from lean body mass & Sr Cr3
*1Manjunath G et al, Curr Opin in Nephrol and Hyper 2001; 10:
*2Cockcroft DW and Gault MH. Nephron 1976;17:31-41
*3Donadio C et al,Asia Pacific Society of Nephrology, Feb 2003.

3. OBJECTIVES The primary objectives of this study were:
To evaluate the the applicability of estimating GFR by Cockcroft-Gault equation (C-G) & Bioelectrical Impedence Analysis (BIA) with the true GFR as measured by the 99mTc-DTPA radioisotope scan in overweight and obese Malaysian subjects with normal serum creatinine

4. STUDY DESIGN

5. 3. Patients who gave informed consent EXCLUSION CRITERIA
INCLUSION CRITERIA
1. Age years old.
2. BMI > 23.
3. Patients who gave informed consent
EXCLUSION CRITERIA
1. Patients with any chronic medical conditions
2. Patients with any known malignancy
3. Patients with acute illness
4. Patients taking traditional medications and/or NSAIDs
5. Patients treated with ACEI or ARB
6. Pregnant woman and lactating mothers.
7. Patients with GFR of ≤ 30 ml/min

6. Table 1: Baseline characteristics and demographic data
Age (years)a
28 (IQR ± 9)
Race (Malay:Chinese:Indian)
94 : 4: 3 (total = 101)
Gender (male: female)
31 : 70
Height (cm)b
158.6 ± 7.4
Weight (kg)a
74.0 (IQR ± 16.6)
Body Mass Index (kg/m²)a
29.6 (IQR ± 6.1) ;
96 obese, 5 overweight
Serum creatinine (44-80µmol/L)a
61.0 (IQR ± 19.0)
a = median (interquartile range; IQR); b = mean ± SD

7. Figure 1: Age Distribution
Median age = 28
IQR = 9
N = 101
Figure 1: Age Distribution 3% 4%
Indian
Chinese
Male
93%
30.7%
Malay
Female
69.3%
Figure 2: Gender Distribution
Figure 3: Distribution of race

8. Table 2: Predictive performance of eGFR by each equation formulae with GFR 99mTc-DTPA
ml/min/
1.73m²
GFR
(99mTc-DTPA) r p
Λ GFR
95%
limits Of
agreement
C-G
141.1 ± 34.6
120.3± 24.5
0.58
0.01*
20.8 ± 35.1
-42.2/97.3
0.0001***
BIA
89.9 ± 19.9
0.52
-30.4 ± 27.2
-82.3/33.4
Values are expressed as mean ± SD; r = Pearson coefficient of determination;
Λ GFR (Mean difference) = [(Mean GFR by prediction equation) - (Mean GFR 99mTc-DTPA)]
SD of Λ GFR = precision of equation formula;
p = 0.05 is taken as significant.

9. Correlation and Agreement of eGFR by C-G with the true GFR (99mTc-DTPA)

10. Correlation and Agreement of eGFR by BIA with the true GFR (99mTc-DTPA)

11. CONCLUSIONS
The C-G formula overestimates GFR because it was originally derived to predict creatinine clearance instead of GFR - creatinine is secreted by the distal renal tubule as well as filtered by the glomerulus
The inclusion of weight as a measure of muscle mass in the C-G formula is another important factor of error - GFR is proportional to body weight in the C-G formula, thus C-G would overestimate GFR in overweight and obese patients
The BIA underestimates GFR - may be due to the lower lean mass in these fat individuals.

12. LIMITATIONS
Our study population was biased towards young, obese, Malay females subjects only - not reflecting the true composition of the Malaysian population.
The findings may not be generalizable to the elderly, males, lean individuals and other ethnic groups.
The delay between recruitment and radioisotope supply resulted in loss of some 29 potential study subjects.

13. REFERENCES
1. Manjunath G, Sarnak MJ and Levey AS. Prediction equations to estimate glomerular filtration rate: an update. Curr Opin in Nephrol and Hyper 2001; 10:
2. Cockcroft DW and Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron 1976;17:31-41
3. Donadio C, Consani C, Ardini M and Lucchesi A. Estimate of GFR from body cell mass and plasma creatinine concentration. Abstract. Asia Pacific Society of Nephrology, Feb 2003.

14. Thank You