Evalution Of Two Formulas In Assessing Glomerular Filtration Rate In Elderly Patients With Chronic Kidney Disease

Objective Cockcorft-Gault formula(CG formula) and simplified MDRD (Modification of Diet in Renal Disease) formula are widely used to estimate glomerlular filtration rate(GFR),however,their agreement with the measurement of GFR with^99mTc-DPTA(the golden standard) in Chinese elderly patients,especially in patients with chronic kidney disease(CKD) is barely studied.The present study is to examine the agreement of these two formulas with the golden standard in Chinese elderly patients with CKD.Methods Renal function was determined by^99mTc-DPTA technique(TGFR) in 154 elderly patients classified as elderly group and in 89 patients under 65 years old classified as non-elderly group.The estimated clearance was determined by equations of CG formula(CG-GFR) and simplified MDRD formula(MDRD-GFR) while serum creatinine was detected meantime.Arithmetic mean,median and quartile interval of the difference between the estimated clearance and the measured clearance were analyzed in both groups.The elderly and the non-elderly groups were subdivided into three and two subgroups(age≥85 years old(yo),75 yo≤age＜84 yo and 65 yo≤age＜75 yo for the elderly,55 yo≤age＜64 yo and age＜55 yo for the non-elderly), respectively,The effects of aging and gender on the deviation of the estimated clearance from TGFR were studied.The agreement of CG formula and simplified MDRD formula with the golden standard was at last compared.Results 1.In the elderly group,the difference between CG-GFR and TGFR had statistical significance(p＜0.05),and arithmetic mean,median and quartile interval of the difference were -11.40ml/(min·1.73m²),-10.79 ml/(min·1.73m²) and(-20.33, -0.11) ml/(min·1.73m²),respectively.In subgroups of the elderly group(age≥85 yo, 75 yo≤age＜84 yo and 65 yo≤age＜75 yo),the differences between CG-GFR and TGFR were all of statistical significance,but the difference between any two of the subgroups was not statistically significant(p＞0.05).In the non-elderly group,the difference between CG-GFR and TGFR had no statistical significance(p＞0.05),and arithmetic mean,median and quartile interval of the difference were -1.37ml/(min·1.73m²),-3.86ml/(min·1.73m²) and(-13.49,14.36)ml/(min·1.73m²), respectively.In the non-elderly group,the difference between CG-GFR and TGFR correlated negatively with the age and the difference was statistically significant in subgroup of which 55 yo≤age＜64 yo but not statistically significant in subgroup of which age＜55 yo.2.In both the elderly and the non-elderly group,the difference between MDRD-GFR and TGFR had no statistical significance in all subgroups classified by age.3.In both male and female group,the difference between CG-GFR and TGFR had statistical significance(p＜0.05),but there was no statistical significance between the two groups.The difference between MDRD-GFR and TGFR had no statistical significance in the male group,but it had statistical significance in the female group(p＜0.05).Arithmetic mean and quartile interval of the difference between MDRD-GFR and TGFR in the female group were -6.56ml/(min·1.73m²) and(-17.92,4.31) ml/(min·1.73m²),respectively.The proportion of the patients in whom TGFR was underestimated by simplified MDRD formula was 65.3%in the female group and 48.5%in the male group,and the difference of the proportion between the two groups had statistical significance(p＜0.05).Conclusions 1.TGFR was underestimated by CG formula in the elderly group with the deviation not affected by aging.TGFR showed the tendency of being underestimated by CG formula in the non-elderly patients while aging.2.TGFR was neither overestimated nor underestimated by simplified MDRD formula in both the elderly group and the non-elderly group.According to the five subgroups classified by age,aging showed no remarkable effect on the difference between MDRD-GFR and TGFR.3.The agreement of the measurement of GFR by^99mTc-DPTA with the estimation of GFR by CG formula was not affected by gender.TGFR was underestimated by simplified MDRD formula in the female group but not in male group.4.The agreement of simplified MDRD formula with golden standard was of no difference with that of CG formula in the non-elderly group,but better than that of CG formula in the elderly group.