The HPC-a Collectogram: A Useful Tool for Determining Collection Processing Volumes

Abstract

Introduction Optimal mobilization is an important step in the autologous hematopoietic cell transplant procedure. Mobilization requires the administration of growth factors such as filgrastim, a granulocyte colony stimulating factor, and plerixafor, a CXCR4 antagonist, that help release hematopoietic progenitor cells (HPC) from the marrow niche. HPCs are differentiated from other cells by their expression of CD34 on the cell surface. Through monitoring of CD34+ cells, the transplant team assesses how well a donor is mobilizing and can adjust mobilization and collection plans accordingly. This enables decision-making on the use of plerixafor and the volume of whole blood to be processed (WBP). Objective We developed the HPC- A Collectogram to help determine the volume of WBP depending on the assumed collection efficiency (CE2). This tool, built in Excel utilizes embedded formulas with input variables including target CD34 dose, dosing weight, blood volume, total WBC, peripheral blood CD34%, PBCD34 count and assumed CE2 (Figure 1). The CE2 at the time of the collection is unknown however an educated guess is made based on the median CE2 for previous collections at our center. The CE2 is a measurement of the apheresis instrument's ability to separate and extract the maximum number of CD34+ cells from cells available in the peripheral blood; yet the CE2 may be heavily influenced by variables such as donor and blood characteristics, as well as apheresis machine software/program and operator adjustments. Method Utilizing the known median CE2 value as a guide, the HPC-A Collectogram can be utilized to predict collection volumes that meet exact collection goals within an acceptable range. The decision to restrict collection based on a calculated processing volume may prevent undesirable side effects of a prolonged apheresis procedure and the over-collection of HPCs. Results For example, Jane Donor, weight 69.9 Kg, height 170.2 cm, WBC 52.2 K/uL, CD34% 0.196: To use the HPC-A Collectogram to guide collection in this patient, the user should: (1) Enter values for prescribed dose and dosing weight to calculate the absolute CD34 dose. (2) Enter current height and weight into the appropriate gender column to calculate donor blood volume. (3) Enter collection day WBC and CD34% as a decimal to determine the PBCD34 and to populate WBP and the target blood volume (BV) (the number of times the donor blood volume will need to be circulated through the apheresis instrument). (4) Choose the target BV to run based on the expected efficiency. For this example, run 3.73 BVs for an expected 40% efficiency to collect 10 million CD34+ cells/kg (Figure 2). Conclusion The HPC-A Collectogram can be a useful tool to more efficiently assist transplant team members in determining the volume of WBP required to meet prescribed dosing goals for hematopoietic cell transplantation.