The deoxyuridine suppression test.

The deoxyuridine suppression (dU) test, first described in 1964, has gained an important place both in the diagnosis of megaloblastic anemias and in the study of vitamin B12 folate interrelationships in the pathogenesis of megaloblastic anemia. The test measures the integrity of the de novo synthetic pathway of DNA synthesis, in which vitamin B12 and folate play an essential role. The exact mechanism of the test is still largely unknown. However, it is probably the most sensitive and specific functional test for the establishment of vitamin B12 and/or folate deficiency. As such, it is an important diagnostic tool in the investigation of patients suspected of suffering from deficiency of either or both of these vitamins. The test may also have applications towards the study of other factors required for the de novo synthesis of DNA.