Does the Inclusion of CD34+ B-cell Progenitors (Hematogones) in Stem Cell Enumeration of Apheresis Product Using ISHAGE Protocol Affect the Final Harvest dose Adequacy and the Outcome of Transplantation? A Single Institution Experience from Southern India.

Purpose: Hematogones have similar antigenic and light scatter properties when compared to CD34+ hematopoietic stem cells (HSC) but they form a separate cluster with dimmer CD45 expression. These should be excluded while enumerating HSC, as their inclusion can overestimate and hence affect the final dose of HSC. However, their exact impact on the outcome of HSC transplant (HSCT) is not entirely known and hence this study was undertaken to address these issues, if any. Methods: This was a retrospective study in which patients undergoing HSCT were included, and flow cytometric enumeration was done on the apheresis product using single platform ISHAGE protocol. The gating of all plots was reviewed and carefully studied for hematogone population which would have otherwise been included in the original gating. Results: Totally 78 patients underwent HSCT during the study period. On re-analysis, it was found that 10/78 (12.8%) cases had a separate hematogone population which was included in the HSC in the original analysis. Out of these 10 cases, 7/51 and 3/27 were in autologous and allogenic subgroup respectively. However, all the ten cases ultimately had adequate final stem cell dose and had successful engraftment. Conclusion: The inclusion of hematogones in CD34+ HSC enumeration of apheresis products did not yield any impact on neither the final dose nor the outcome of transplant in this study. However, it is recommended to exclude them from the final count when they are > 10% of the final HSC lest it overestimate the final harvest dose and outcome of HSCT.