Factors Affecting the Determination of CD34+ Cells in Blood and Leukapheresis Products

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The number of peripheral blood stem cell (PBSC) transplantations permanently increased in recent years. Therefore, the determination of CD34+ cells in blood and leukapheresis products represents an elementary and obligatory technique for quantitation of PBSC. However, although the first national protocols for flow-cytometric determination of CD34+ cells have been published, no uniformly accepted guidelines for quantitation of progenitor cells are currently available. Therefore, many centers perform individual protocols for determination of CD34+ cells by different techniques. Preanalytical aspects such as the manner of apheresis or anticoagulation of PBSC products may affect the enumeration of CD34+ cells as well as details in laboratory handling and processing of samples. In particular, the selection and usage of monoclonal antibodies and erythrocyte lysing procedures have a major influence on the determination of CD34+ cells. Accordingly, the first national and international multicenter studies showed large differences in the determination of CD34+ cells. This article reflects the main factors affecting the flow-cytometric determination of CD34+ cells in blood and leukapheresis products as evaluated by own investigations and described in a recently published German consensus protocol. Moreover, alternative techniques for quantitation of CD34+ cells are shortly discussed.