Measurement of the kidney function in patients with rheumatoid arthritis: plasma cystatin C versus 51Cr-EDTA clearance.
OBJECTIVE
Knowledge of the usefulness of cystatin C measurement in the detection of chronic kidney disease in patients with rheumatoid arthritis (RA) is scant. The purpose of this study was to evaluate the ability of plasma cystatin C- and creatinine-based methods to predict glomerular filtration rate (GFR) and classify chronic kidney disease in RA patients.


METHODS
The study population consisted of 64 RA patients aged 41-86 years. Comparisons were made between measured plasma creatinine, cystatin C, creatinine clearance and GFR estimated by the Cockcroft-Gault (CG) and the Modification of Diet in Renal Disease (MDRD) formulas. The plasma clearance of (51)Cr-EDTA served as a reference.


RESULTS
The Pearson correlation coefficients between plasma clearance of (51)Cr-EDTA and the markers of GFR were calculated. The correlation coefficients were 0.800 for plasma creatinine, 0.863 for cystatin C, 0.866 and 0.904 for GFR values estimated by MDRD and CG and 0.922 for plasma creatinine clearance. Statistically significant differences were detected between the correlation coefficients of plasma creatinine and GFR estimated by CG (p = 0.0412) and plasma creatinine and creatinine clearance (p = 0.0099). Creatinine clearance and the MDRD and CG formulas proved to be better at identifying GFR <90 ml/min than plasma creatinine or cystatin C.


CONCLUSIONS
We recommend using the CG formula or creatinine clearance for the estimation of the GFR of RA patients instead of solely creatinine or cystatin C in clinical work.
Karstila
Krista
K
Department of Internal Medicine, Tampere University Hospital, Tampere, Finland. krista.karstila@fimnet.fi
Harmoinen
Aimo P T
AP
Lehtimäki
Terho J
TJ
Korpela
Markku M
MM
Mustonen
Jukka T
JT
Saha
Heikki H T
HH
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000150:complications*; D002860:Chromium Radioisotopes / Q000493:pharmacokinetics; D003404:Creatinine / Q000097:blood / Q000652:urine; D055316:Cystatin C; D015891:Cystatins / Q000097:blood*; D004492:Edetic Acid / Q000493:pharmacokinetics; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007118:Immunoassay; D007674:Kidney Diseases / Q000175:diagnosis* / Q000209:etiology / Q000378:metabolism; D007677:Kidney Function Tests / Q000379:methods*; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D009391:Nephelometry and Turbidimetry; D012680:Sensitivity and Specificity
C525030:CST3 protein, human; D002860:Chromium Radioisotopes; D055316:Cystatin C; D015891:Cystatins; D004492:Edetic Acid; D003404:Creatinine