Relationship of serum cystatin C to peritoneal and renal clearance measures in peritoneal dialysis: a cross-sectional study.
BACKGROUND
Clinical management of peritoneal dialysis patients includes assessments of peritoneal and renal clearances of the low-molecular-weight endogenous solutes creatinine and urea. Cystatin C is a low-molecular-weight protein used as a glomerular filtration rate marker. We investigated whether serum cystatin C concentration is related to peritoneal and renal clearances of creatinine and urea.


METHODS
Cross-sectional study.


METHODS
119 patients undergoing peritoneal dialysis in a single dialysis unit.


METHODS
Peritoneal, renal, and total clearance of urea as Kt/V(urea) and creatinine as weekly creatinine clearance (C(Cr)). Residual renal function (RRF) as the average of renal clearances of urea and creatinine.


METHODS
Serum concentrations of cystatin C measured by using a particle-enhanced nephelometric immunoassay.


RESULTS
Serum cystatin C concentration was related inversely to RRF (Spearman rank correlation coefficient [r(s)] = -0.65; P < 0.001), total weekly C(Cr) (r(s) = -0.52; P < 0.001), and total Kt/V(urea) (r(s) = -0.23; P = 0.01). In a multiple regression model, weight, normalized protein catabolic rate, and RRF had independent effects on serum cystatin C concentrations. Additional multiple regression models showed that only the renal components of Kt/V(urea) and weekly C(Cr) contributed to serum cystatin C concentrations.


CONCLUSIONS
Absence of reference GFR method.


CONCLUSIONS
Serum cystatin C concentrations reflect predominantly renal, not peritoneal, clearance. Serum cystatin C measurement may be a simple and practical alternative to measurement of RRF.
Delaney
Michael P
MP
Department of Renal Medicine, East Kent Hospitals NHS Trust, Kent and Canterbury Hospital, Canterbury, Kent, UK.
Stevens
Paul E
PE
Al Hasani
Mohammed
M
Stowe
Helen J
HJ
Judge
Caroline
C
Lamb
Edmund J
EJ
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001202:Ascitic Fluid / Q000378:metabolism*; D015415:Biomarkers / Q000378:metabolism; D015331:Cohort Studies; D003404:Creatinine / Q000378:metabolism* / Q000652:urine; D003430:Cross-Sectional Studies; D055316:Cystatin C; D015891:Cystatins / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D010530:Peritoneal Dialysis; D011237:Predictive Value of Tests; D012107:Research Design; D014508:Urea / Q000378:metabolism* / Q000652:urine
D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D014508:Urea; D003404:Creatinine