title: Changes in dietary protein intake has no effect on serum cystatin C levels independent of the glomerular filtration rate.
abstract: 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 m(2)) 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 m(2)) 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.
authors.affiliation: Division of Nephrology, Department of Medicine, Tufts Medical Center, Boston, Massachusetts 02111, USA. ntangri@tuftsmedicalcenter.org
authors.forename: Navdeep
authors.initials: N
authors.lastname: Tangri
authors.forename: Lesley A
authors.initials: LA
authors.lastname: Stevens
authors.forename: Christopher H
authors.initials: CH
authors.lastname: Schmid
authors.forename: Yaping Lucy
authors.initials: YL
authors.lastname: Zhang
authors.forename: Gerald J
authors.initials: GJ
authors.lastname: Beck
authors.forename: Tom
authors.initials: T
authors.lastname: Greene
authors.forename: Josef
authors.initials: J
authors.lastname: Coresh
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Levey
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D003404:Creatinine / Q000097:blood; D003430:Cross-Sectional Studies; D055316:Cystatin C / Q000097:blood*; D004044:Dietary Proteins / Q000008:administration & dosage*; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000178:diet therapy / Q000503:physiopathology; D055815:Young Adult
chemical_list: D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D004044:Dietary Proteins; D003404:Creatinine