Elsevier

Kidney International

Volume 79, Issue 4, 2 February 2011, Pages 471-477
Kidney International

Original Article
Changes in dietary protein intake has no effect on serum cystatin C levels independent of the glomerular filtration rate

https://doi.org/10.1038/ki.2010.431Get rights and content
Under an Elsevier user license
open archive

Cystatin C is being considered as a replacement for serum creatinine in the estimation of the glomerular filtration rate (GFR); however, its plasma levels might be affected by factors other than the GFR, such as protein intake. We performed a post hoc analysis of the data in the Modification of Diet in Renal Disease study, in which we compared serum creatinine and cystatin C levels in 741 patients with available estimates of protein intake at baseline prior to their randomization to diets containing various amounts of protein, and at 2 years of follow-up in 426 of these patients in whom a cystatin C measurement was available. The 503 patients in study A (GFR 25–55 ml/min per 1.73 m2) had been assigned a low (0.58 g/kg per day) or a usual (1.3 g/kg per day) protein intake, and the 238 participants in study B (GFR 13–24 ml/min per 1.73 m2) were assigned a very low (0.28 g/kg per day) or the low protein intake. In either study group, lowering the dietary protein intake reduced the change in creatinine, but did not have a significant change in cystatin C. Thus, in patients with moderate-to-severe chronic kidney disease, serum cystatin C unlike serum creatinine was not affected by dietary protein intake independent of changes in GFR. Hence, cystatin C may allow more accurate estimates of GFR than creatinine for patients with reduced protein intake. Further study of other non-GFR determinants of cystatin C is needed before the widespread adoption.

KEYWORDS

creatinine
glomerular filtration rate
protein restriction

Cited by (0)

The preliminary findings from this paper were presented at Renal Week 2009 in San Diego, California.