Relation between Microalbuminuria and Estimated Glomerular Filtration Rate by Creatinine and Cystatin C

Song, Younghee; Park, Soonho; Seo, Yielhea; An, Jeongyeal; Kim, Kyung Hee; Park, Pilwhan

Abstract

BACKGROUND
In the routine "Life-turning point" medical checkup, we use estimated glomerular filtration rate (eGFR), which calculated from Cockcroft-Gault (CG) equation, to assume early stage renal disease and perform reexamination, if it is below 60 mL/min. Suppose their body weights and creatinine concentrations are the same, older patient's eGFR decreases 40-50% of younger one and in patients over 70, their eGFR is decreased in 45% although their creatinines are in normal range. Microalbuminuria is single most important index in the early diagnosis of glomerular dysfunction. Authors compared the positiveness of microalbuminuria with decreased eGFR which calculated using creatinine and cystatic C in the old age groups to evaluate the adequacy of eGFR in the routine "Life-turning point" medical checkup.
METHODS
From June to August 2008, 314 adults [172 male and 142 female, 60+/-14 (mean age+/-SD)] who visited Gachon university Gil hospital were included. We freezed their serum and urine in -70degrees C and thawed within 4 weeks to measure serum creatinine, cystatin C, urine microalbumin and creatinine (Hitachi 7600, Hitachi High. Technologies Co., Osaka, Japan).
RESULTS
1 subject (0.7%) was reported with eGFR below 60 mL/min in the group of subjects under 66 years old, while 45(26.2%) were noticed in the group over 66 years old. There is a significant difference statistically between positive rate of microalbumiuria and eGFR by cystatin C than creatinine in the group over 66 years old (P=0.042 vs. P<0.001).
CONCLUSIONS
The CG eGFR is useful for screening and reevaluation the renal function because many patients over 66 years, which is the point of the "Life-turning point" medical checkup, represents lower eGFR. Cystatin C eGFR is more closely related to the microalbuminuria positive rate than creatinine eGFR.