THE DEOXYURIDINE SUPPRESSION TEST IN HIV-1 POSITIVE PATIENTS - THE ROLE OF AZYDOTHYMIDINE (AZT)

The deoxyuridine suppression test (dUST) was used to evaluate human im munodeficiency virus type 1 positive (HIV-1) patients with low serum l evels of vitamin B-12 and/or low red cell folate and to assess any pos sible interferences of azydothymidine (AZT) in this test. The dUST was studied in 29 HIV-1 positive patients, 18 without low serum vitamin B -12 or low red cell folate and 11 with low serum vitamin B-12 (6 patie nts), low red cell folate (4 patients) and 1 case with both. The role of AZT was studied using different concentrations (0.2, 2.5 and 10 mu M/ml) in 2 groups: 1 group of 5 patients with vitamin B-12 and/or fola te deficiency and another group consisting of 13 healthy subjects. Met hotrexate (MTX) (50 mu g/ml) was added to induce a folate megaloblasti c pattern in the latter group. Results of the dUST in the HIV-1 group without low levels of serum vitamin B-12 fell within the health-relate d reference interval values. A vitamin B-12 deficiency was only detect ed in 1 case in the HIV-1 group with low serum vitamin B-12, although a folate deficiency pattern was observed in the 4 patients with low re d cell folate. In the healthy subjects AZT induced a dose-dependent de crease of the MTX-induced folate megaloblastic pattern. The pattern wa s also observed in the group of patients with vitamin B-12 or folate d eficiency, although AZT did not entirely interfere with the dUST. The effect of AZT on the dUST was attributed to a decrease in the incorpor ation of the isotope in the absence of deoxyuridine. The dUST is usefu l in differentiating vitamin B-12 deficient patients from HIV-1 infect ed patients with low levels of serum vitamin B-12.