Most techniques for CD34+ cell enumeration are dual platform-assays. That is, they derive absolute numbers of CD34+ cells from either the flow cytometrically assessed per cent (%) CD34+ cells within the nucleated cells and/or the white blood cell count from a haematology cell analyser. Recently, so-called single-platform assays have been developed, in which the absolute number of CD34+ cells is directly derived from a single flow cytometric measurement. The present study aims to compare the variation between eight laboratories in CD34+ cell counts from paired assays of 15 samples using a common single (ProCOUNT(TM)) and the local dual-platform method. Six laboratories used the 'SIHON' and two the 'ISHAGE' protocol for CD34+ cell enumeration. Use of the single-platform method reduced the inter-laboratory variation in per cent and absolute numbers of CD34+ cells, as measured by interquartile ranges, by half but did not lead to an appreciable reduction of the inter-laboratory variation in white blood cell counts. Thus, part of the reduced inter-laboratory variation obtained with ProCOUNT(TM) may have been a result of the use of standardized procedures and reagents to detect CD34+ cells. In order to eliminate any variation arising from the use of different local protocols for percentage of CD34+ cell assessments, a comparison was made of the ProCOUNT(TM)-derived absolute CD34+ cell numbers (i.e. single platform) with the dual-platform absolute CD34+ cell numbers calculated by multiplying ProCOUNT(TM)-derived percentage of CD34+ cells and with the corresponding haematology analyser-derived white blood cell count. Regardless, the interquartile ranges of absolute CD34+ cell numbers remained almost a factor of two smaller with the use of the single platform method. Thus, these results suggest that single-platform methodology can reduce the variation in absolute CD34+ cell numbers between laboratories.

Absolute counts, CD34, Flow cytometry, Haematopoietic stem cells,
International Journal of Laboratory Hematology
Department of Medical Oncology

Gratama, J.W, Braakman, E, Kraan, J, Lankheet, M.J.M, Leveringh, W.H.B.M, van den Beemd, M.W.M, … Preijers, F.W.M.B. (1999). Comparison of single and dual-platform assay formats for CD34+ haematopoietic progenitor cell enumeration. International Journal of Laboratory Hematology, 21(5), 337–346. doi:10.1046/j.1365-2257.1999.00236.x