High prevalence of cobalamin deficiency in Guatemalan schoolchildren: associations with low plasma holotranscobalamin II and elevated serum methylmalonic acid and plasma homocysteine concentrations.
Studies conducted in Guatemala, Mexico, and Venezuela have found high prevalences of low plasma cobalamin (vitamin B-12) concentrations in infants and children. It is not known whether these low cobalamin concentrations are accompanied by altered metabolic functions. We sought to assess the prevalence of cobalamin deficiency in Guatemalan children by using sensitive and specific markers of deficiency. Children (n = 553) were screened for low plasma cobalamin. Those with low plasma cobalamin (< 162 pmol/L) were matched by age, grade, and sex to those with marginal (162-221 pmol/L) and adequate (> 221 pmol/L) concentrations. In this matched subset (n = 180), additional biochemical indicators of cobalamin deficiency were measured. Of the 553 children screened, 11% had low plasma cobalamin and an additional 22% had marginal concentrations. The prevalences of elevated serum methylmalonic acid (MMA), plasma homocysteine, or both were significantly higher in children with low and marginal plasma cobalamin than in children with adequate plasma cobalamin. Mean serum MMA was high in all groups compared with values reported in other populations. Mean plasma holotranscobalamin II concentrations were significantly lower in children with low rather than marginal or adequate plasma cobalamin. However, holotranscobalamin II was a less sensitive indicator of cobalamin depletion than was MMA. Biochemical markers of cobalamin deficiency confirmed that the cobalamin status of children with low and marginal plasma cobalamin is inadequate to support normal metabolic function.