The CD34+ cell fraction in bone marrow and blood is not universally predictive of CFU-GM.

We have measured the presence of granulocyte-macrophage colony forming cells (CFU-GM) and CD34+ cells in blood and bone marrow. We have compared these hematopoietic cell assays using regression analysis. We have found that under the limited and specific case of blood cells from an individual recovering from myelo-suppressive chemotherapy, the fraction of cells that is CD34 positive is predictive of the number of granulocyte-macrophage colonies (CFU-GM) which will grow. This result is in agreement with published data. We have found, however, that in bone marrow aspirates, or in the blood of individuals recovering from cyclophosphamide chemotherapy and receiving either granulocyte-macrophage colony stimulating factor (G-CSF) or folinic acid (FA) therapy, there is poor correlation between CD34+ cell fraction and CFU-GM. Accordingly, the use of CD34+ fraction cannot be relied upon to substitute for the CFU-GM assay in assessing the hematopoietic cell content of blood or bone marrow samples.