Vitamin B-12 metabolism in HIV-infected patients in the age of highly active antiretroviral therapy: role of homocysteine in assessing vitamin B-12 status

Background: Before the advent of highly active antiretroviral therapy (HAART), 20% and 10% of HIV-infected patients had low vitamin B-12 and red blood cell folate (RBCF) concentrations, respectively. However, few patients had real vitamin B-12 deficiency. Objective: We evaluated the prevalence of low vitamin B-12 and RBCF concentrations in HIV-infected patients receiving HAART and the usefulness of serum homocysteine (sHcy) for differentiating patients with deficiency from those with harmlessly low vitamin B-12. Design: The prevalence of low vitamin B-12 and RBCF was evaluated in 126 HIV-infected patients receiving HAART. Moreover, sHcy concentrations were evaluated in 40 HIV-infected patients with low vitamin B-12 and in 37 HIV-infected patients with low RBCF and were compared with those in 128 HIV-infected patients with normal vitamin B-12 and RBCF. sHcy was used to monitor treatment with vitamin B-12 and folic acid in 28 patients (24 with low vitamin B-12 and RBCF and 4 with hyperhomocysteinemia but normal vitamin B-12 and RBCF). Results: The prevalence of low vitamin B-12 was significantly lower in patients receiving HAART than in previously studied patients who did not receive HAART (8.7% compared with 27%). Nine of the 40 patients (22.5%) with low vitamin B-12 (≤ 200 pmol/L) had hyperhomocysteinemia (> 17.5 μmol homocysteine/L). Nineteen (51.4%) of the 37 patients with low RBCF (≤ 580 nmol/L, percentile 10) had hyperhomocysteinemia. Among the 9 patients with an RBCF concentration ≤ 450 nmol/L (percentile 2.5), all had hyperhomocysteinemia. The treatment with vitamin B-12 and folic acid normalized sHcy concentrations. Conclusions: The prevalence of low vitamin B-12 decreased after the introduction of HAART. The study of sHcy is useful for detecting HIV-infected patients with low vitamin B-12 and real deficiency.