(P-TS-62) Invalid Babesia Testing Results In Hematopoietic Progenitor Cell Apheresis Donor

Babesiosis is a tick-borne disease, caused primarily in the United States by the protozoa Babesia microti that infects red blood cells (RBCs). Transmission can also occur by transfusion of RBCs collected from asymptomatic, infected blood and cell therapy donors. Cell therapy donors at our institution are routinely tested for Babesia using a nucleic acid test (NAT) licensed by the FDA for blood and cell therapy donor screening, however, invalid results were occasionally observed. We investigated potential causes associated with invalid Babesia NAT results in cellular therapy donors.

Study

Design/Methods:

We reviewed infectious disease marker (IDM) test results for all cell therapy donors between July 2021 and May 2024. For all donors, peripheral blood specimens were collected for IDM testing on the day of apheresis. All HPC, Apheresis (HPC, A) donors were mobilized with granulocyte colony stimulating factor (G-CSF) +/- chemotherapy or plerixafor. Bone marrow and mononuclear cell donors were unmobilized. Testing was performed at Creative Testing Solutions (CTS). Whole blood lysates were tested individually using a licensed nucleic acid test (NAT) targeting Babesia 18S rRNA (Procleix Babesia assay-Grifols Diagnostic Solutions). In November 2022, we implemented additional Babesia NAT for all cell therapy donors prior to mobilization.

Results/Findings:

Between July 2021 and May 2024, 432 cellular therapy products were collected, including 199 HPC, A (autologous and allogeneic) collections. Thirty-three HPC, A donor samples (16.6%) had invalid Babesia results for samples collected on the day of apheresis. Donors with invalid Babesia results were comparable in demographics to those with valid results. In order to have complete IDM testing results for donor eligibility determination, some donors with invalid test results from the day of collection underwent repeat Babesia NAT several days after mobilization (4/33), or had additional testing prior to mobilization (10/33), all of which showed negative results. No positive results were observed in any donor samples, and no invalid results were observed in samples from unmobilized donor samples. Mobilized donor samples with invalid Babesia NAT had higher mean white blood cell (WBC) counts than mobilized samples with non-reactive Babesia results (mean ± standard deviation 59.64 ± 21.22 vs 39.33 ± 12.08, p< 0.001). 

Conclusions:

Invalid Babesia NAT results were observed in a significant proportion of mobilized HPC, A donors, but not in unmobilized donor samples with normal WBC counts. Donor samples with invalid results had higher mean WBC counts than those with valid results. Our results suggest that elevated WBC counts in mobilized HPC, A donors may interfere with Babesia NAT assays.