title: Variability of fasting and post-methionine plasma homocysteine levels in normo- and hyperhomocysteinaemic individuals.
abstract: To assess the variability of plasma homocysteine levels, fasting and post-methionine homocysteine levels were measured twice, at baseline and after follow-up of 1-4 months, in 16 individuals with normal and 26 with elevated homocysteine levels after methionine loading. The intra-individual coefficients of variation varied from 15 to 23% for fasting and post-methionine homocysteine levels, whether these levels were within the normal range or not. As a result, test-retest agreement was poor when subjects were dichotomized as having 'normal' or 'abnormal' homocysteine levels (itself a questionable concept). There was a relation between the average post-methionine homocysteine levels (at the first and second measurement) and the difference between both measurements (r = 0.37, P = 0.016). In normohomocysteinaemic individuals, delta (i.e., the difference between baseline and follow-up) fasting homocysteine and delta post-methionine homocysteine were correlated negatively with delta folate serum levels: r = -0.64, P = 0.007 and r = -0.50, P = 0.05, respectively. Individuals homozygous for the 677 C-->T mutation in the 5,10-methylenetetrahydrofolate reductase gene showed a greater variation of fasting homocysteine levels than those homozygous for the wild type (P = 0.017). In summary, we suggest that there is a substantial intra-individual variability in plasma homocysteine levels over time and that this variability is significantly related to the variability in serum folate levels, especially in normohomocysteinaemic individuals.
authors.affiliation: Institute for Cardiovascular Research, Vrije Universiteit, Amsterdam, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: van den Berg
authors.forename: S C
authors.initials: SC
authors.lastname: de Jong
authors.forename: W
authors.initials: W
authors.lastname: Devillé
authors.forename: J A
authors.initials: JA
authors.lastname: Rauwerda
authors.forename: C
authors.initials: C
authors.lastname: Jakobs
authors.forename: G
authors.initials: G
authors.lastname: Pals
authors.forename: G H
authors.initials: GH
authors.lastname: Boers
authors.forename: C D
authors.initials: CD
authors.lastname: Stehouwer
mesh_terms: D045103:5,10-Methylenetetrahydrofolate Reductase (FADH2); D000328:Adult; D000704:Analysis of Variance; D005215:Fasting / Q000502:physiology*; D005260:Female; D005492:Folic Acid / Q000097:blood / Q000502:physiology; D006710:Homocysteine / Q000097:blood* / Q000502:physiology; D006720:Homozygote; D006801:Humans; D020138:Hyperhomocysteinemia / Q000175:diagnosis* / Q000503:physiopathology*; D008297:Male; D008715:Methionine / Q000378:metabolism; D042965:Methylenetetrahydrofolate Reductase (NADPH2); D008875:Middle Aged; D009154:Mutation; D010088:Oxidoreductases / Q000235:genetics; D018709:Statistics, Nonparametric
chemical_list: D006710:Homocysteine; D005492:Folic Acid; D008715:Methionine; D010088:Oxidoreductases; D045103:5,10-Methylenetetrahydrofolate Reductase (FADH2); D042965:Methylenetetrahydrofolate Reductase (NADPH2)