Cystatin C is a sensitive marker for detecting a reduced glomerular filtration rate when assessing chronic kidney disease in patients with rheumatoid arthritis and secondary amyloidosis.
OBJECTIVE
Chronic kidney disease is a predictor of end-stage renal disease, and evaluating the glomerular filtration rate (GFR) is necessary to make a definite diagnosis. We assessed the utility of serum cystatin C (cysC) for identifying a reduced GFR in patients who have rheumatoid arthritis (RA) with secondary amyloidosis.


METHODS
Fifty patients with RA and secondary amyloidosis (mean age 60.9+/-11.2 years; 45 women) were evaluated. The revised 24-h creatinine clearance (r24-hC(Cr)), which was determined by multiplying the original value by 0.719, was used as a reference for the GFR. The screening potential of the serum cysC and some estimates of the GFR calculated from the serum cysC (cysC-eGFR: eGFR(Hoek) and eGFR(Rule)) for detecting a reduced GFR (r24-hC(Cr)<60 mL/min/1.73 m(2)) were analysed.


RESULTS
Both cysC-eGFRs were strongly correlated with the r24-hC(Cr) (eGFR(Hoek), r=0.846, p<0.001; eGFR(Rule), r=0.820, p<0.001). The difference between the average eGFR(Rule) (37.1+/-31.2 mL/min/1.73m(2)) and average r24-hC(Cr) (35.3+/-30.9 mL/min/1.73 m(2)) was small, whereas eGFR(Hoek) and sCr-eGFR were higher than eGFR(Rule) and r24-hC(Cr). In receiver operating characteristic (ROC) curve analyses of a reduced GFR, serum cysC gave a greater area under the curve (AUC=0.958) than the sCr-eGFR (0.939-0.942). The specificity and positive predictive value (PPV) reached 100% when serum cysC >1.365 mg/L was used.


CONCLUSIONS
Serum cysC can identify a reduced GFR more accurately than sCr-eGFRs. Serum cysC >1.09 mg/L (i.e. eGFR(Rule)<60 mL/min/1.73 m(2)) could be a marker of a reduced GFR, and serum cysC >1.365 mg/L would strongly suggest a reduced GFR in patients who have RA with secondary amyloidosis.
Sato
H
H
Division of Clinical Nephrology and Rheumatology, Niigata University Graduate School of Medical and Dental Sciences, Faculty of Medicine, Niigata University, Chuoku, Niigata City, Japan.
Kuroda
T
T
Tanabe
N
N
Ajiro
J
J
Wada
Y
Y
Murakami
S
S
Sakatsume
M
M
Nakano
M
M
Gejyo
F
F
D000368:Aged; D000686:Amyloidosis / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology; D019540:Area Under Curve; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000032:analysis / Q000378:metabolism; D015331:Cohort Studies; D003404:Creatinine / Q000097:blood; D055316:Cystatin C / Q000032:analysis* / Q000097:blood; D018450:Disease Progression; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011336:Probability; D011379:Prognosis; D012372:ROC Curve; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index
D015415:Biomarkers; D055316:Cystatin C; D002097:C-Reactive Protein; D003404:Creatinine