Age- and gender-specific reference intervals for total homocysteine and methylmalonic acid in plasma before and after vitamin supplementation

Abstract

We present reference intervals for total homocysteine and methylmalonic acid in plasma based on samples from 126 women (ages 20-85 years, median 49 years) and 109 men (ages 20-84 years, median 50 years). The central 0.95 interval for methylmalonic acid was 0.08-0.28 micromol/L. Supplementation with cyanocobalamin caused a nonsignificant decrease in methylmalonic acid. Supplementation with folic acid caused a decrease in homocysteine concentrations, with data analysis identifying two significantly different clusters: 182 subjects with the lowest initial concentrations (7.76 +/- 1.54 micromol/L, mean +/- SD) and the smallest decrease (1.26 +/- 0.96 micromol/L), and 53 subjects with the highest initial concentrations (12.33 +/- 2.04 micromol/L) and greatest decrease (4.14 +/- 1.32 micromol/L). We argue in favor of the age- and gender-specific central 0.95 intervals obtained for the 182 subjects before being supplemented with folic acid: 4.6-8.1 micromol/L for subjects at <30 years; 4.5-7.9 micromol/L for women, ages 30-59 years; 6.3-11.2 micromol/L for men, ages 30-59 years; and 5.8-11.9 micromol/L for subjects at >60 years.

Determinants of changes in plasma homocysteine in hyperthyroidism and hypothyroidism

“…Independent determinants of pre-treatment plasma tHCys concentrations in this study were fT 4 and age. The increase of plasma tHCys concentration with advancing age is well known (Rasmussen et al, 1996).…”

Erythrocyte folate, plasma folate and plasma homocysteine during normal pregnancy and postpartum: a longitudinal study comprising 404 Danish women

“…Blood samples for measurement of P-homocysteine were collected in tubes containing heparin as anticoagulant and with sodium fluoride added to a final concentration of 4 g/L blood. P-total homo-cysteine was measured by a modification (11) of the gas chromatography-mass spectometric technique developed by Stabler et al (12); the intra-assay coefficient of variation was 2.6% and 1.1% at plasma concentrations of 7.0 and 23.1 lmol/L, respectively (11,13).…”

Hyperhomocysteinemia and thrombosis

“…Normal ranges vary widely in different populations because they are affected by several lifestyle determinants (see above). When determined in a population with adequate vitamin intake (58,59), the upper limit of the normal range may be as low as 12 µmol/L. Because fasting tHcy levels are affected by gender, different cutoff points should be used for men and women.…”