Volume determination methods for hematopoietic progenitor cell products collected by apheresis

Background aims: CD34⁺ cell count of hematopoietic progenitor cell products is often first determined using a product sample, with the final reported cell count obtained by multiplying cell count from the sample by the total product volume. Product volume may be determined by apheresis instruments used for collection or calculated based on specific gravity (SG). Here the authors sought to determine the discrepancies between these methods and the impact on patient care. Methods: A total of 262 products collected from 176 donors by apheresis were retrospectively reviewed. Volumes calculated by apheresis instruments were compared with volumes calculated based on SG. CD34⁺ cell/kg doses based on volumes from apheresis instruments and SG were also compared. Furthermore, among 42 patients who required multiple collections, the authors determined whether different calculation methods would have changed the number of procedures required. Results: The volumes for 253 products (96.6%) and CD34⁺ cell/kg doses for 257 products (98.1%) generated from apheresis instruments and SG were similar. Products with discrepant volumes when calculated using different methods were not associated with delayed engraftment. Forty patients who underwent multiple collections (95.2%) were under their collection goals during their first collection and would have required multiple procedures regardless of which method was used to calculate product volumes. Conclusions: Volumes determined based on SG did not provide a clear benefit over volumes determined by apheresis instruments. Hence, variation in volume calculation methods across different laboratories is likely to lead to minimal impact on patient care.