Urinary Cystatin C and Tubular Proteinuria Predict Progression of Diabetic Nephropathy
- Sang Soo Kim, MD1,2,
- Sang Heon Song, MD, PHD1,2,
- In Joo Kim, MD, PHD1,2⇓,
- Yun Kyung Jeon, MD1,
- Bo Hyun Kim, MD, PHD1,
- Ihm Soo Kwak, MD, PHD1,
- Eun Kyung Lee, RPH3 and
- Yong Ki Kim, MD, PHD4
- 1Department of Internal Medicine, Pusan National University Hospital, Busan, Korea
- 2Biomedical Research Institute, Pusan National University Hospital, Busan, Korea
- 3Endocare Pharmacy, Busan, Korea
- 4Kim Yong Ki Internal Medicine Clinic, Busan, Korea
- Corresponding author: In Joo Kim, .
S.S.K. and S.H.S. contributed equally to this study.
OBJECTIVE The aim of this study was to evaluate the association of urinary cystatin C, a tubular damage marker, with the progression of type 2 diabetic nephropathy.
RESERCH DESIGN AND METHODS The baseline values of serum and urinary cystatin C were measured as primary parameters and those of urinary nonalbumin protein (NAP) were measured as secondary parameters. In this prospective observational study, a total of 237 type 2 diabetic patients were followed up for 29 months (13–44 months).
RESULTS Both the urinary cystatin C-to-creatinine ratio (CCR) and NAP-to-creatinine ratio (NAPCR) were significantly different according to the degree of albuminuria. Both markers had strongly positive correlations at baseline. After adjusting for several clinical factors, both urinary CCR and NAPCR had significant associations with the decline of the estimated glomerular filtration rate (eGFR) (r = 0.160, P = 0.021; r = 0.412, P < 0.001, respectively). Urinary CCR had positive correlations with the decline of eGFR in the subpopulation of patients with eGFR ≥60 mL/min/1.73 m2. In patients with eGFR ≥60 mL/min/1.73 m2 and normoalbuminuria, only urinary NAPCR showed a significant association with the decline of eGFR; urinary CCR did not. In multivariate regression analysis, the number of patients who progressed to chronic kidney disease stage 3 or greater was higher in those in the upper tertiles of both the urinary levels of cystatin C and NAP than in those in the lower tertiles.
CONCLUSIONS The results of this study suggest that urinary cystatin C and NAP may be predictors of the progression of type 2 diabetic nephropathy.
- Received May 3, 2012.
- Accepted August 10, 2012.
- © 2012 by the American Diabetes Association.
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