Serum cystatin C advantageous compared with serum creatinine in the detection of mild but not severe diabetic nephropathy.
OBJECTIVE
To determine whether serum cystatin C is more accurate than serum creatinine in the detection of diabetic nephropathy, also after adjustment for age.


METHODS
Forty-one patients with type 1 and 82 patients with type 2 diabetes were evaluated with serum creatinine, serum cystatin C, and (51)Cr-EDTA clearance (reference method). Cystatin C was measured by a particle-enhanced turbidimetric method and creatinine by an enzymatic method. Statistical estimations were performed both without and with age adjustment created by z-scores for (51)Cr-EDTA clearance, creatinine, and cystatin C. The cut-off levels for glomerular filtration rate (GFR) ((51)Cr-EDTA clearance) were 60 and 80 mL min(-1) 1.73 m(-2), respectively, in absolute values and 80, 90 and 95% CIs, respectively, in age-adjusted values (z-scores).


RESULTS
Estimations without age adjustment showed significantly (P = 0.0132) closer correlation for cystatin C (r = 0.817) versus (51)Cr-EDTA clearance as compared with creatinine (r = 0.678). However, when using age-adjusted values, the correlation for cystatin C and creatinine, respectively, versus (51)Cr-EDTA clearance did not differ. When comparing the diagnostic utilities for serum cystatin C versus serum creatinine in manifest renal impairment (GFR < 60 mL min(-1) 1.73 m(-2) or z-scores <-1.28 SD), there were no significant differences between the two markers whether age adjusted or not. However, for diagnosing mild nephropathy (GFR < 80 mL min(-1) 1.73 m(-2) or z-score -0.84 SD), serum cystatin C is significantly more useful.


CONCLUSIONS
Serum cystatin C performed better compared with serum creatinine even when measured enzymatically, to detect mild diabetic nephropathy. However, serum creatinine was as efficient as serum cystatin C to detect advanced diabetic nephropathy.
Christensson
A G
AG
Department of Nephrology and Transplantation, Malmö University Hospital, SE-205 02 Malmö, Sweden. anders.christensson@medforsk.mas.lu.se
Grubb
A O
AO
Nilsson
J-A
JA
Norrgren
K
K
Sterner
G
G
Sundkvist
G
G
D000328:Adult; D000367:Age Factors; D000368:Aged; D000419:Albuminuria / Q000209:etiology; D015415:Biomarkers / Q000097:blood; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C; D015891:Cystatins / Q000097:blood*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000150:complications / Q000175:diagnosis; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000150:complications / Q000175:diagnosis; D003928:Diabetic Nephropathies / Q000097:blood / Q000150:complications / Q000175:diagnosis*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007677:Kidney Function Tests / Q000379:methods; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012372:ROC Curve
D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D003404:Creatinine