Cystatin C enhances glomerular filtration rate estimating equations in kidney transplant recipients.
BACKGROUND
The glomerular filtration rate (GFR) estimating equation incorporating both cystatin C and creatinine perform better than those using creatinine or cystatin C alone in patients with reduced GFR. Whether this equation performs well in kidney transplant recipients cross-sectionally, and more importantly, over time has not been addressed.


METHODS
We analyzed four GFR estimating equations in participants of the Angiotensin II Blockade for Chronic Allograft Nephropathy Trial (NCT 00067990): Chronic Kidney Disease Epidemiology Collaboration equations based on serum cystatin C and creatinine (eGFR (CKD-EPI-Creat+CysC)), cystatin C alone (eGFR (CKD-EPI-CysC)), creatinine alone (eGFR (CKD-EPI-Creat)) and the Modification of Diet in Renal Disease study equation (eGFR (MDRD)). Iothalamate GFR served as a standard (mGFR).


RESULTS
mGFR, serum creatinine, and cystatin C shortly after transplant were 56.1 ± 17.0 ml/min/1.73 m(2), 1.2 ± 0.4 mg/dl, and 1.2 ± 0.3 mg/l respectively. eGFR (CKD-EPI-Creat+CysC) was most precise (R(2) = 0.50) but slightly more biased than eGFR (MDRD); 9.0 ± 12.7 versus 6.4 ± 15.8 ml/min/1.73 m(2), respectively. This improved precision was most evident in recipients with mGFR >60 ml/min/1.73 m(2). For relative accuracy, eGFR (MDRD) and eGFR (CKD-EPI-Creat+CysC) had the highest percentage of estimates falling within 30% of mGFR; 75.8 and 68.9%, respectively. Longitudinally, equations incorporating cystatin C most closely paralleled the change in mGFR.


CONCLUSIONS
eGFR (CKD-EPI-Creat+CysC) is more precise and reflects GFR change over time reasonably well. eGFR (MDRD) had superior performance in recipients with mGFR between 30 and 60 ml/min/1.73 m(2).
Division of Renal Diseases and Hypertension, Department of Medicine, University of Minnesota, Minneapolis, Minn., USA.
Aleksandra
A
Kukla
Naim
N
Issa
Scott
S
Jackson
Richard
R
Spong
Meredith C
MC
Foster
Arthur J
AJ
Matas
Michael S
MS
Mauer
John H
JH
Eckfeldt
Hassan N
HN
Ibrahim
D000328:Adult; D000368:Aged; D065095:Calcineurin Inhibitors; D003404:Creatinine / Q000097:blood; D003430:Cross-Sectional Studies; D055316:Cystatin C / Q000097:blood / Q000737:chemistry*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D007483:Iothalamic Acid / Q000032:analysis; D007677:Kidney Function Tests; D016030:Kidney Transplantation / Q000379:methods*; D008297:Male; D008875:Middle Aged
D065095:Calcineurin Inhibitors; D055316:Cystatin C; D007166:Immunosuppressive Agents; D007483:Iothalamic Acid; D003404:Creatinine