Correlation Analysis of CD34+ Cell Counts between External Vendor and in-House Apheresis Testing to Support Laboratory Transition

Hematopoietic stem cell transplantation (HSCT) is a crucial treatment approach for hematologic malignancies. The quantity of CD34+ cells is the most significant factor influencing engraftment kinetics and hematologic recovery, which directly affects patients' outcomes. Flow cytometry using International Society of Hematotherapy and Graft Engineering (ISHAGE) protocols is recognized as the gold standard for counting CD34+ cells. While many U.S. hospitals have relied on external reference labs for CD34+ cell enumeration, the growing demands for faster turnaround times, advancements in cytometry technology, and improved standardization are prompting a shift toward in-house testing. Evaluated the correlation and agreement between CD34+ cell counts by the American Red Cross (ARC) reference lab and MetroHealth's ISHAGE-compliant protocol. Validate the reliability of the in-house flow cytometry protocol CD34+ counting cells, ensuring compliance with international standards and clinical requirements. Enhance the operational advantages of transitioning to in-house CD34+ cell testing, focusing on improvements in turnaround time, cost-effectiveness, and patient care logistics. 75 autologous HSCT collections at MetroHealth were analyzed. Paired results were obtained in 63 cases. 9 lacked paired data, and 3 were excluded due to sample preparation errors: the CD45/μL vs. WBC/μL ratio differed by more than 40%. Apheresis products were tested at MetroHealth on the day of collection and shipped to ARC (Philadelphia) for next-day testing. Both sites utilized Becton Dickinson (BD) Stem Cell Enumeration Kits in conjunction with BD flow cytometers (Canto or Lyric at MetroHealth; Lyric at ARC). Statistical analysis was performed using GraphPad Prism X, with significance defined as p < 0.05. To assess consistency between MetroHealth's in-house CD34+ enumeration protocol and the ARC reference method, we analyzed the 63 matched HSCT collections using a paired two-sample t-Test and Pearson correlation. The mean CD34+ count from ARC was 1,318 cells/μL, while MetroHealth reported a mean of 1,334 cells/μL, showing no statistically significant difference (p = 0.46). The variance was comparable, with ARC at 2,286,477 and MetroHealth at 2,393,958 supporting dispersion homogeneity. The Pearson correlation coefficient was r = 0.987, indicating a strong linear relationship. The Bland-Altman analysis showed a mean bias of +16.57 cells/μL and standard deviation of 176.91 cells/μL, with 95% limits of agreement ranging from -330.17 to +363.31 cells/μL. MetroHealth's in-house CD34+ cell enumeration demonstrates a strong correlation with ARC values, confirming its reliability for transplant decision-making. These findings support the shift to in-house CD34+ testing, which enhances program autonomy and reduces turnaround times.