Standardization of the CFU-GM Assay: Advantages of Plating a Fixed Number of CD34+ Cells in Collagen Gels

We investigated whether plating a stable amount of CD34+ cells improves the CFU-GM assay. Data of CFU-GM assays performed with leukaphereses products in two transplant centers using a commercial collagen-based medium and unified CFU-GM scoring criteria were pooled and analyzed according to the numbers of CD34+ cells plated. A first series of 113 CFU-GM assays was performed with a fixed number of mononuclear cells (i.e., a variable number of CD34+ cells). In these cultures the CFU-GM/CD34 ratio varied according to the number of CD34+ cells plated: median CFUGM/CD34 ratios were 1/6.2 to 1/6.6 for grafts containing <2% CD34+ cells, vs. 1/10.2 for grafts containing ≥2% CD34+ cells. The median CFU-GM/CD34 ratio also varied depending on pathology: 1/9.3 for multiple myeloma (MM), 1/6.8 for Hodgkin's disease (HD), 1/6.5 for non-Hodgkin lymphoma (NHL), and 1/4.5 for solid tumors (ST). A second series of 95 CFU-GM assays was performed with a fixed number of CD34+ cells (220/ml). The range of median CFU-GM/CD34 rat...