Homocysteine: relationship to serum cobalamin, serum folate, erythrocyte folate, and lobation of neutrophils.

Serum levels of total homocysteine were studied in the following: 26 healthy adults; 79 hospitalised patients in whom serum cobalamin, serum folate, and erythrocyte folate were greater than 230 pmol/L, 12 nmol/L, and 600 nmol/L, respectively; 32 hospitalised patients whose serum cobalamin was less than 147 pmol/L, compared to 25 patients whose serum cobalamin was greater than 147 pmol/L but unmatched in any other parameter; and 194 patients in whom samples were sent for determination of cobalamin and folate from a neurological service. None of this last group had megaloblastic anaemia. There was a relationship between the elevated concentrations of total homocysteine in serum and low concentrations of serum cobalamin and of erythrocyte folate. This relationship was most evident in samples with serum cobalamin < 86 pmol/L and erythrocyte folate < 335 nmol/L, although elevated homocysteine levels were found in some samples where serum cobalamin and erythrocyte folate levels were greater than these. Serum folate correlated poorly with serum total homocysteine. There was only a poor-to-fair correlation of neutrophil lobe counts to total serum homocysteine.