Cystatin C levels in functionally anephric patients undergoing dialysis: the effect of different methods and intensities.
OBJECTIVE
Cystatin C, a low molecular weight protein, is produced by nucleated cells, filtered by glomeruli, and degraded by tubules at a constant rate. Its serum concentration has been proposed as a marker of GFR. Its size should make it dialyzable. It is hypothesized that serum cystatin C levels are influenced by the method and intensity of dialysis received.


METHODS
This is a cross-sectional pilot study of cystatin C in functionally anephric dialysis patients. It was measured predialysis in 14 patients on conventional (3 to 5 h, 3 x wk) hemodialysis; eight on nocturnal hemodialysis (three to seven nights, 6 to 8 h); three on daily hemodialysis (6 d, 1(1/2) to 2(1/2) h); and 10 on automated peritoneal dialysis. All had urea kinetic studies and values for single pool Kt/V (Sp Kt/V), standard weekly Kt/V (Std Kt/V), and protein equivalent of nitrogen appearance (nPNA; g/kg/d). C reactive protein (CRP; mg/L) and thyroid stimulating hormone (TSH; mIU/L) were measured as factors known to influence cystatin C.


RESULTS
There was no correlation between cystatin C and Sp Kt/V, but there was a significant inverse linear correlation with Std Kt/V and there were significant differences between treatment modalities in cystatin C levels and in Std Kt/V. The estimation of cystatin C was reliable and stable over 3 to 6 wk and its levels uninfluenced by nPNA, CRP, or TSH.


CONCLUSIONS
Serum cystatin C levels are influenced by the method and intensity of dialysis and may have a role in treatment adequacy monitoring.
Al-Malki
Najila
N
Department of Medicine, and London Health Sciences Centre, Nephrology Division, The University of Western Ontario, London, Canada.
Heidenheim
Paul A
PA
Filler
Guido
G
Yasin
Abeer
A
Lindsay
Robert M
RM
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002097:C-Reactive Protein / Q000032:analysis; D003430:Cross-Sectional Studies; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D009392:Nephrectomy; D010865:Pilot Projects; D006435:Renal Dialysis; D013972:Thyrotropin / Q000097:blood; D014508:Urea / Q000378:metabolism
D055316:Cystatin C; D014508:Urea; D013972:Thyrotropin; D002097:C-Reactive Protein