Vitamin B12 Content of Circulating Leukocytes as an Aid in the Differentiation of the Acute Leukemias

From 25 patients with acute leukemia 116 specimens of leukocytes were assayed microbiologically for total vitamin B₁₂ to determine if variation in vitamin B₁₂ content would help in differentiating the acute leukemias. The mean cell vitamin B₁₂ levels (μμg./10⁸ cells) in the different types of leukemia were: lymphoblastic 464, myeloblastic 1058 and monocytic 200. Cell vitamin B₁₂ levels above the normal range (100-800 μμg./10⁸ cells) are suggestive of myeloblastic leukemia. The only elevated cell vitamin B₁₂ levels comparable to those found in myeloblastic leukemia were in reticulum cell leukemia, and this type of leukemia was not difficult to diagnose morphologically. Blast cells contained more vitamin B₁₂ than mature cells of the same series; there was a significant positive correlation between the percentage of blast cells and cell levels of total vitamin B₁₂ in both lymphoblastic and myeloblastic leukemia.