Free Serum Vitamin B₁₂ Level in Certain Hematologic Disorders

The variation of the free fraction of serum vitamin B₁₂ level was studied in certain hematologic disorders. In normals, the mean ratio of free to total vitamin B₁₂ was 10.2 per cent. In leukemias—chronic myeloid, acute myeloid and acute lymphatic—the mean value of free vitamin B₁₂ was higher than normal. In chronic myeloid and acute lymphatic leukemias, the free vitamin B₁₂ level did not on an average exceed 20 per cent of the total. In acute myeloid leukemia, the free fraction was relatively more increased, constituting 31.1 per cent of the total on an average. In aplastic anemia, the mean values of free vitamin B₁₂ and the ratio (31.2 per cent) of free to total vitamin B₁₂ were higher than normal. The patterns presented by acute myeloid leukemia and aplastic anemia appeared to be more or less similar.