Cystatin C does not detect acute changes in glomerular filtration rate in early diabetic nephropathy.
BACKGROUND
The measurement of renal functional reserve (acute change in glomerular filtration rate [GFR] after protein load) allows the detection of sub-clinical renal dysfunction and has prognostic implications in diabetes. Our aim was to test cystatin C as an index of GFR and renal functional reserve.


METHODS
GFR was measured by C(Sinistrin) at baseline and after protein load in 28 diabetic patients with serum creatinine <1.2 mg/dL. The C(Sinistrin) was compared with cystatin C, serum creatinine, creatinine clearance, and Cockcroft-Gault formula.


RESULTS
Baseline C(Sinistrin) ranged from 67-172 mL/min. Regression analysis showed an overall low relationship between C(Sinistrin) and the indirect markers of GFR. The highest correlation with C(Sinistrin) was obtained for cystatin C clearance (R(2) = 0.58, r = 0.76, p < 0.001), the 1/serum cystatin C (R(2) = 0.58, r = 0.76, p < 0.001), and serum cystatin C (R(2) = 0.52, r = 0.72, p < 0.001). Renal functional reserve was preserved in 6 of 28 patients. There was no significant change in cystatin C in response to protein load.


CONCLUSIONS
Wide variation in baseline GFR emphasizes the need for the early detection of renal dysfunction. Cystatin C correlated best with C(Sinistrin) at baseline, but did not detect renal functional reserve.
Mueller
Thomas F
TF
Department of Medicine, Division of Nephrology and Transplantation Immunology, University of Alberta, Edmonton, Canada. tmueller@ualberta.ca
Raeder
Juliane
J
Oettl
Karl
K
Zitta
Sabine
S
Klausmann
Gert
G
Estelberger
Willibald
W
Luyckx
Valerie A
VA
Reibnegger
Gilbert
G
D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D001786:Blood Glucose / Q000032:analysis; D003404:Creatinine / Q000097:blood / Q000652:urine; D055316:Cystatin C; D015891:Cystatins / Q000097:blood*; D003928:Diabetic Nephropathies / Q000378:metabolism / Q000503:physiopathology*; D004044:Dietary Proteins; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D009844:Oligosaccharides / Q000493:pharmacokinetics
D015415:Biomarkers; D001786:Blood Glucose; C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D004044:Dietary Proteins; D009844:Oligosaccharides; D003404:Creatinine; C064636:sinistrin