Novel markers of early neutrophilic and monocytic engraftment after hematopoietic stem cell transplantation

Background: Numerous studies tried to find new markers that after hematopoietic stem cell transplantation predict engraftment earlier than the conventional marker, absolute neutrophil count (ANC >500/μL). Early engraftment prediction can be achieved by a marker that reflects the release of neutrophils and monocytes into the leukopenic peripheral blood. Methods: We analyzed blood cell parameters, including cell population data such as volume, conductivity, and light scatter in 77 patients who underwent HSCT (allogeneic, n= 63; autologous, n=11) to detect possible markers. Results: We identified 2 early engraftment markers of neutrophils (NEUTRO) and monocytes (MONO); a pair of mean-volume-neutrophils (MNV) and mean-conductivity-neutrophils (MNC) for NEUTRO; and a pair of mean-volume-monocytes (MMV) and mean-conductivity- monocytes (MMC) for MONO. The new markers showed distinct patterns for early engraftment wherein 1) on the engraftment day, MNV peaked as MNC notched simultaneously for every case, and 2) MMV peaked as MMC notched simultaneously in most cases. Engraftment was predicted 3.8±2.7 days earlier than by ANC in 74 successful engraftment cases by using NEUTRO and/or MONO: 1) 72 cases (97.3%), in which NEUTRO and/or MONO predicted earlier engraftment than ANC, 2) 1 case, in which the 3 markers predicted engraftment on the same day, and 3) 1 case, in which NEUTRO predicted engraftment on the same day as ANC and MONO failed to predict engraftment. Conclusions: By analyzing the data from daily complete blood counts, engraftment can be predicted approximately 4 days earlier than ANC >500/μL using NEUTRO as a base marker and MONO as a supplementary marker.