Low serum vitamin B12 levels in an outpatient HIV-infected population.

A retrospective review was conducted on serum vitamin B12 levels in an HIV-infected outpatient cohort, many of whom received antiretroviral therapy. B12 levels were obtained at most staging visits (every six months) and when clinically indicated. For each serum B12 level, laboratory values and clinical symptoms were recorded. Thirty-two patients (32/251 or 13%) had at least one low B12 level (<211pg/mL) during the course of their HIV infection. Within two years of their initial HIV presentation, 6/57 patients had a low serum B12. Using multiple linear regression analysis, a higher serum B12 level was significantly associated with higher folate levels, African-American race, and lower mean corpuscular volume. B12 levels increased significantly after initiating antiretroviral therapy (416 vs 535 pg/mL, P=0.04). In conclusion, low serum B12 levels occur commonly among HIV-infected patients, even at early stages without overt symptoms of B12 deficiency. Antiretroviral therapy may increase serum B12 levels.