(P-BC-80) Titer Testing Patterns in O-Positive LTOWB Donors: A Quantitative Analysis of Stability and Fluctuation

Background/Case Studies: The interest in transfusing whole blood has grown due to military studies showing success resuscitating injured personnel. This practice has moved to civilian settings, with Low-titer O Whole Blood (LTOWB) increasingly used for emergency transfusions when a patient’s blood type is unknown. To reduce reaction risks in non-O patients receiving mismatched plasma, LTOWB is transfused if anti-A1 and anti-B titers are confirmed to be low titer. We define low titer when Anti-A1 and Anti-B are < 1:200. We test every donation regardless of donor frequency.

Study

Design/Methods: We performed one dilution titers for anti-A1 and anti-B on all O positive whole blood donations intended for LTOWB use. Titers were determined by diluting the donor plasma with isotonic saline to a 1:200 dilution. The diluted plasma was then tested against A1 and B cells using a standardized tube method, centrifuged immediately, the cell buttons were resuspended and observed for agglutination. Any agglutination was considered high titer, and no agglutination was considered low titer. Results were recorded as the number of donations with titers < 1:200 and >1:200.

Results/Findings: Titers were performed on 1005 donors from 5/1/2020 to 3/31/2025. Of these, 846 (84.2%) have always titered < 1:200 and 31 (3.1%) have always titered >1:200, and 128 (12.7%) have fluctuated between < 1:200 and >1:200. Among the donors with consistent results, the majority (628) had 2 donations that were all < 1:200, while 179 had 3 donations that were all < 1:200, and 32 had 4 donations all < 1:200. Of the donors with fluctuating results, most (97) had 1 donation < 1:200 and 1 donation >1:200. Only 27 donors had 0 donations < 1:200 and 2 donations >1:200, with 4 donors having 0 donations < 1:200 and 3 donations >1:200, indicating a consistent high-titer profile. (See Table 1)

Conclusions: Our findings demonstrate that while most O positive donors (84.2%) consistently maintain low anti-A1 and anti-B titers (< 1:200), a significant portion (12.7%) show fluctuation in their titers between donations. This variability highlights the importance of testing each donation rather than qualifying donors based on previous titer results. The small percentage (3.1%) of donors who consistently present with high titers could be excluded from LTOWB programs. Understanding these patterns of titer variability can help blood centers optimize their LTOWB donor recruitment and testing strategies, potentially reducing costs while maintaining safety standards.