Increased plasma total homocysteine is too nonspecific; methylmalonic acid determination, although posing fewer problems of specificity, is complex and expensive; and the deoxyuridine suppression test
is too unwieldy for practical use.
The other 9 cobalamin-deficient sera were from patients with mild preclinical deficiency [see Carmel (3) for background], which had been documented by metabolic tests of cobalamin status, such as the deoxyuridine suppression test
and methy1malonic acid and homocysteine assays.
Therefore, tests for other cobalamin markers have been developed, such as the holo-transcobalamin II concentration in serum (15), the deoxyuridine suppression test, or the functional markers methylmalonic acid (MMA) and total homocysteine (tHcy) (16).
The deoxyuridine suppression test (dUST) is theoretically sound (27, 33), but is expensive and labor-intensive, and therefore impractical for large-scale use.
Comparison of the deoxyuridine suppression test with serum levels of methylmalonic acid and homocysteine in mild cobalamin deficiency.