Background: Although the colony-forming cell (CFC) assay provides the most relevant information regarding the functional potential of progenitors in a unit of umbilical cord blood (UCB), technical challenges associated with this assay have made it difficult to standardize the assay among testing laboratories. The purpose of this study was to assess the reproducibility of a newly developed functional assay (HALO SPC-QC [HALO], HemoGenix, Inc.). This test is based on the principle that cellular proliferation responses to cytokine stimuli are proportional to intracellular ATP levels from progeny cells generated in culture from progenitors.
Study design and methods: Results of the HALO assay were evaluated at two geographically distinct sites with matched aliquots from 12 different UCB units.
Results: A significant correlation between the two sites for total nucleated cell counts was observed (r = 0.98, p < 0.001). Similarly, a strong correlation between HALO results from both sites was observed (r = 0.94, p < 0.001). Also, despite using different methods at each site for the CFC assay, results from the two sites correlated (r = 0.79, p = 0.002). A good correlation between the CFC and HALO assays (r = 0.73, p < 0.005), however, was only observed at the site with the same cytokine cocktail for both the CFC and the HALO assays.
Conclusion: These results support the notion that the HALO assay is a reasonable approach for measuring the functional potential of hematopoietic progenitors in UCB. Moreover, because the final readout for the HALO assay is instrument based, unlike the CFC assay, which requires a subjective enumeration of colonies, the HALO assay may be more amenable to standardization.