Authors (including presenting author) :
Kong WS(1), Lam CY(1), Ho WMS (1), Leung MP(1), Lee PWP(1)(2)
Affiliation :
(1) Department of Paediatrics and Adolescent Medicine, Hong Kong Children's Hospital
(2) Department of Paediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, 1/F, New Clinical Building, Queen Mary Hospital, The University of Hong Kong
Introduction :
Peripheral blood is the common source of stem cells in haematopoietic stem cell transplant (HSCT) and the Spectra Optia apheresis machine is used for the peripheral blood stem cell (PBSC)harvest in the Hong Kong Children’s Hospital. It uses the automated interface management (AIM) system to control the cells collection by interpreting the darkness of cells and providing information to the operator to adjust the collection level. Therefore, the collection efficiency will be affected if the AIM system information to the operator is inaccurate by not considering the characteristics of other blood components such as low mean corpuscular volume (MCV), thus adversely affecting the product yield. We hereby report two cases of stem cell harvest from donors with abnormal red blood cells done in our hospital.
Objectives :
1) To arouse awareness of apheresis operators in handling donors with abnormal blood components
2) To apply the strategies to overcome the abnormalities
3) To optimize the product yield
Result & Outcome :
A 3-year old child with relapsed acute lymphoblastic leukemia underwent a haploidentical PBSC transplant with her mother as the donor. However, her mother was found to have Hemoglobin H disease (HbH) with microcytic anemia (MCV = 54.8 fL, normal range: 80.9-93.9 fL) during donor workup. The donor was mobilized using granulocyte–colony-stimulating factor (G-CSF) and received top-up red cell transfusion one day before the harvest. Peripheral CD34+ cell count was performed daily and the pre-harvest CD34+ cell count was 60 cells/uL (minimum requirement = 10 cells/uL). Studies reported that the yield of CD34+ stem cell harvest is often lower in donors with low MCV. After discussing with the medical team and the manufacturer, we collect stem cells by lowering collection preference and increasing the centrifugation speed for this donor. Eventually, stem cells were collected at a deeper location with a colour algorithm of 3-4% while the rate of centrifugation was limited to the size of the venous access. Although the product yield was adequate for the child (10x10^6/kg CD34+ based on the child’s body weight), it was less than half of the predicted CD34+ cell yield (20-25x10^6/kg) by calculation . All cells were transfused to the child without surplus product for cryopreservation. The child had neutrophil and platelet engraftment on D+11 and D+17 respectively and achieved 100% donor chimerism on D+30. However, she developed molecular relapse on D+60 and required donor lymphocyte infusion.
Another case was a 9-year old child with beta-thalassemia major who underwent a haploidentical PBSC transplant. Backup bone marrow was harvested before transplant and extra processing (bone marrow processing, BMP) for volume reduction by plasma depletion was performed before cryopreservation. An additional irradiated packed cell from a random donor was added to the BMP bag before the procedure to meet the apheresis machine’s operation requirement. Unexpectedly, the product yield was only 0.64 x 10^6 CD34+ cells/kg. Learning from the previous case and after discussing with the medical team, we repeated the processing by collecting at a darker colour 5-6% according to the colour algorithm, and eventually, a CD34+ cell dose of 3.89 x 10^6/kg was collected in the product.
Conclusion: The outcome of product yield is not only associated with the CD34+ count, but also with the characteristic of other cells including red blood cells. Adjustments in the apheresis parameters are needed to optimize peripheral blood or bone marrow stem cell harvest from donors with abnormal RBC.
