title: Cystatin C as a determinant of fasting plasma total homocysteine levels in coronary artery disease patients with normal serum creatinine.
abstract: Serum creatinine, a surrogate for both renal function and homocysteine generation, is a determinant of fasting plasma total homocysteine levels in coronary artery disease (CAD) patients. We hypothesized that among stable-CAD patients with normal creatinine levels (ie, </=1.4 mg/dL), serum cystatin C, a more sensitive indicator of glomerular filtration rate, would better predict fasting total homocysteine levels in comparison with serum creatinine. Fasting plasma total homocysteine, folate, vitamin B(12), and pyridoxal 5'-phosphate levels, along with serum cystatin C, creatinine, and albumin levels, were determined in 164 consecutive stable-CAD patients (mean+/-SD age, 61+/-9 years; 78.7% men) whose serum creatinine level was </=1.4 mg/dL. All subjects were examined at least 3 to 4 months after the widespread availability of cereal grain flour products fortified with folic acid. General linear modeling with ANCOVA revealed that serum cystatin C (P<0.001), B(12) (P<0.001), age (P=0.002), albumin (P=0.008), and sex (P=0.024) were independent determinants of fasting total homocysteine levels. Cystatin C alone determined over half of the variability (ie, R(2)) in total homocysteine levels accounted for by these 5 independent regressors. In contrast, creatinine, folate, and pyridoxal 5'-phosphate were not independently predictive of fasting total homocysteine levels (P>0.2). Consistent with the impact of folic acid fortification of cereal grain flour in the general population, only 1 of the CAD subjects (0.6%) had a plasma folate level <3 ng/mL. We conclude that serum cystatin C levels may reflect subtle decreases in renal function that independently predict fasting total homocysteine levels among stable-CAD patients with normal serum creatinine.
authors.affiliation: Divisions of General Internal Medicine and Cardiology, Memorial Hospital of Rhode Island, Providence, RI 02860. abostom@loa.com
authors.forename: A G
authors.initials: AG
authors.lastname: Bostom
authors.forename: L
authors.initials: L
authors.lastname: Bausserman
authors.forename: P F
authors.initials: PF
authors.lastname: Jacques
authors.forename: G
authors.initials: G
authors.lastname: Liaugaudas
authors.forename: J
authors.initials: J
authors.lastname: Selhub
authors.forename: I H
authors.initials: IH
authors.lastname: Rosenberg
mesh_terms: D000328:Adult; D000368:Aged; D003327:Coronary Disease / Q000097:blood* / Q000503:physiopathology; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C; D015891:Cystatins / Q000097:blood*; D005215:Fasting / Q000097:blood*; D005260:Female; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D007668:Kidney / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012016:Reference Values
chemical_list: C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D006710:Homocysteine; D003404:Creatinine