Quality assurance of progenitor cell content of apheresis products: a comparison of clonogenic assays and CD34+enumeration

The most common methods used for evaluation of the haematopoietic stem cell content of peripheral blood apheresis products are the colony forming cell assay and the enumeration of CD34+ cells by flow cytometry. The Canadian A pheresis Group and the Canadian Bone Marrow Transplant Group established a multicentre study to compare the reproducibility of colony forming cell ass ays and CD34+ enumeration by flow cytometry in six transplant centres routi nely performing haematopoietic stem cell apheresis, Over a 5-month period in 1996, 31 fresh apheresis samples were shipped by o vernight courier for testing at six centres to perform CD34+ enumeration by flow cytometry and clonogenic assays. The mean coefficient of variation an d range for the following assays were: cell count 36% (2.6-148%), CFU-GM 82 % (46-123%), CD34+ absolute/kg 60% (14-174%) and CD34+ per cent 42% (12-84% ). The wide variation in cell count in this pilot study highlights the difficu lties related to provision of samples for quality assessment programmes. Re sults showed poor interinstitutional reproducibility even among selected sa mples with similar cell counts for both CFC and CD34+ assays demonstrating the need for development and implementation of an interinstitutional qualit y assurance programme for haematopoietic stem cell assessment. Provision of a reliable source of testing material will be a necessary next step.