Evaluation of the deoxyuridine suppression test by using whole blood samples from folic acid-supplemented subjects

We performed the deoxyuridine suppression test (dUST) along with assessment of folate and vitamin B-12 status in blood specimens from 136 normal women and 109 women with cervical dysplasia. All tests were repeated at 2, 4, and 6 mo in subjects with dysplasia during a randomized, double-blind intervention trial in which 50 received a 10-mg daily oral folic acid supplement (F group) and 59 received a placebo (P group). Median folate concentration increased fivefold in plasma and threefold in erythrocytes of F group beginning at the second months and remained elevated whereas concentrations of the P group remained unchanged. Vitamin B-12 values did not vary significantly in either group. The dUST value decreased from 10.4 +/- 4.6% (means +/- SD) pretreatment to 4.5 +/- 4.7% in F group after 2 mo (p less than 0.001). The dUST values had significant negative correlation with plasma and erythrocyte folate concentrations. However, erythrocyte folate had the greatest power to distinguish P group from F group.