Use of cystatin C-based estimations of glomerular filtration rate in patients with type 2 diabetes.
OBJECTIVE
The Modification of Diet in Renal Disease (MDRD) equation has recognised limitations when using estimated GFR in persons at risk of chronic kidney disease. Equations based on cystatin C provide an alternative method. We compared performance of the MDRD equation with a selection of cystatin C-based formulae for estimation of GFR in normoalbuminuric patients with type 2 diabetes.


METHODS
Estimated GFR was calculated using the MDRD equation and the cystatin C formulae proposed by several investigator teams. Isotopic GFR was measured using plasma clearance of (51)Cr-EDTA.


RESULTS
We studied 106 participants, of whom 83 (78%) were men with the following characteristics, mean (SD): age 61 (9) years, HbA(1c) 7.10 (1.27)%, creatinine 89.0 (12.7) micromol/l, cystatin C 0.859 (0.234) mg/l and isotopic GFR 104.5 (20.1) ml min(-1) 1.73 m(-2). MDRD estimated GFR was 77.4 (13.6) ml min(-1) 1.73 m(-2) (p < 0.05 for difference from isotopic GFR). Cystatin C-based calculations of estimated GFR were: Perkins 124.5 (31.8), Rule 90.0 (30.0), Stevens (age) 96.0 (30.4) and Stevens (creatinine) 85.6 (19.0) ml min(-1) 1.73 m(-2) (p < 0.05 for difference with isotopic GFR). For Arnal's, MacIsaac's and Tan's formulae cystatin-C estimated GFR were 101.7 (34.8), 102.1 (27.0) and 101.6 (27.8) ml min(-1) 1.73 m(-2), respectively (p = NS for difference with isotopic GFR). Cystatin C-based formulae were less biased and, with the exception of Perkins' formula, more accurate to within 10% of isotopic GFR than MDRD.


CONCLUSIONS
Performance of cystatin C equations was superior to MDRD in normoalbuminuric patients with type 2 diabetes. These results support further evaluation of cystatin C for estimation of GFR in persons at risk of chronic kidney disease.
Diabetes Research Unit, Llandough University Hospital, Penlan Road, Llandough, Penarth, Cardiff, UK. rachudleigh@hotmail.com
R A
RA
Chudleigh
R L
RL
Ollerton
G
G
Dunseath
R
R
Peter
J N
JN
Harvey
S
S
Luzio
D R
DR
Owens
D000368:Aged; D000925:Anticoagulants / Q000493:pharmacokinetics; D015415:Biomarkers / Q000097:blood*; D002860:Chromium Radioisotopes; D055316:Cystatin C / Q000097:blood*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology; D003928:Diabetic Nephropathies / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology; D004492:Edetic Acid / Q000493:pharmacokinetics; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007668:Kidney / Q000502:physiology; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D018570:Risk Assessment / Q000379:methods; D012307:Risk Factors
D000925:Anticoagulants; D015415:Biomarkers; D002860:Chromium Radioisotopes; D055316:Cystatin C; D004492:Edetic Acid