Clinical correlates of subnormal vitamin B12 levels in patients infected with the human immunodeficiency virus

Objectives: To determine the prevalence and describe the clinical correlates of subnormal cobalamin levels in subjects infected with the human immunodeficiency virus (HIV), and to assess its relationship to virus‐mediated immunosuppression and/or anti‐viral therapy. Setting: Outpatient referral clinic in tertiary care hospital. Patient population: 200 HIV infected individuals. Study design: Descriptive cross sectional survey, with prospective follow‐up in a subgroup of patients before and after initiation of zidovudine therap. Measures: Routine complete blood count, serum B12 assay, CD4 counts. Serum homocysteine levels, and Schilling tests were performed on subgroups of study subjects. Results: Subnormal serum B12 levels were found in 61 subjects (30.5%). B12 deficient subjects were more likely to be taking zidovudine. (P = .007). Serum homocysteine levels were significantly higher in patients with subnormal cobalamin levels but were unrelated to CD4 counts or zidovudine use, and were rarely outside of the normal range. Malabsorption of vitamin B12 as evidenced by abnormal Schilling tests was more likely among patients with more advanced HIV disease, or gastrointestinal symptoms but was not necessarily associated with low B12 levels. Conclusions: Decreased cobalamin levels are found frequently in HIV disease, especially among those treated with zidovudine. Evidence of B12 malabsorption is found among those with more advanced disease and gastrointestinal symptoms.