Determining the optimal time for peripheral blood stem cell harvest by detecting immature cells (immature leukocytes and immature reticulocytes) using two newly developed automatic cell analyzers.

To determine the optimal time of peripheral blood stem cell harvest (PBSCH), we evaluated the usefulness of the detection of immature hematopoietic cells (immature leukocytes and reticulocytes) using newly developed automatic cell analyzers, and compared the results with those of conventional CD34 measurement by flow cytometry (FCM). The presence of immature leukocytes and reticulocytes was calculated as immature leukocyte information (IMI)-positive rate and high fluorescence reticulocyte (HFR)-positive rate by multi-item autoanalyzers. Both the IMI-positive rate and HFR-positive rate positively correlated with the CD34-positive rate and was more highly correlated with the colony forming units-mixed (CFU-Mix) count in peripheral blood. In addition, they positively correlated not only with the CD34-positive rate, but also with the colony forming units-granulocyte/macrophage (CFU-GM) count and CFU-Mix count in harvested stem cell juice. These findings imply that the parameters of IMI and HFR could be used for determining the optimal time of PBSCH, and could also be useful for quantifying stem cells.