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 μmol/L. Supplementation with cyanocobalamin caused a nonsignificant decrease in methylmalonic acid. Supplementation with folio 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 μmol/L, mean ± SD) and the smallest decrease (1.26 ± 0.96 μmol/L), and 53 subjects with the highest initial concentrations (12.33 ± 2.04 μmol/L) and greatest decrease (4.14 ± 1.32 μmol/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 μmol/L for subjects at <30 years; 4.5-7.9 μmol/L for women, ages 30-59 years; 6.311.2 μmol/L for men, ages 30-59 years; and 5.8-11.9 μmol/L for subjects at >60 years.