BioBridge Global San Antonio, Texas, United States
Background/Case Studies: Anti-A and anti-B antibodies pose a risk of acute hemolytic transfusion reactions in recipients with the corresponding antigen. Continued debate on the titer of anti-A and B and which antibody class, IgM or IgG, to test to ensure optimal safety. The US military uses a single titer cutoff of < 1:256 of IgM anti-A and B as safe in non-group O recipients. Our center has been providing low titer O positive whole blood (LTOWB) for pre-hospital transfusion using the cutoff of < 1:256 for over six years. There is presently no nationalized agreement on titer level cutoff for classification as low titer and levels used at various centers may vary based on those institutions medical director’s discretion.With the increasing interest in LTOWB pre-hospital programs, our center’s data on the effect of race on isoagglutinin titers may help with targeting recruitment.
Study
Design/Methods: In October 2017, our center started a LTOWB program by screening O Rh(D) positive male fixed-site donors with a history of 2 or more donations for isoagglutinin levels. In September 2022, O Rh(D) positive females with a similar donation history were added to our program if they had never been pregnant or had tested negative for HLA antibodies. Our program defines “low titer” as < 1:256 IgM Anti-A and Anti-B (IgM anti-A/B) antibodies, in concordance with the military protocol. Plasma from ethylenediaminetetraacetic acid (EDTA) samples was tested using saline (0.9%) diluent. Diluted plasma (50uL) was mixed with 50uL of commercially available A1 and B cells, incubated at room temperature for 5 minutes, centrifuged for 15 seconds at 3600 rpm, and read for agglutination.Reactivity for either anti-A or anti-B at 1:256 constituted a positive result. Donor race was retrieved from the blood establishment computer system. For race, donor choices are Caucasian/White, Hispanic, Black/African American, Asian/Pacific Islander, American Indian, Multi-race or Other, or Undeclared.
Results/Findings: Since October 2017, a total of 18,086 unique donors have been tested with race declared in 10,018. For donors tested on multiple occasions, a single high titer result constituted a high titer categorization for this data analysis. Table 1 shows the data stratified by race. Using Fisher Exact, the prevalence of high titer IgM anti-A/B antibodies was statistically higher in Hispanic and Black/African American donors compared to Caucasians/Whites. No statistically significant difference in titer prevalence was seen between Caucasian/White race and Asian/Pacific Islander, American Indian or Multi/Other race. Conclusions: In this data set, Caucasian/White, Asian/Pacific Islander and Multi race donors are the best target populations to screen for a LTOWB program. If additional data confirms the titer prevalences within the Asian/Pacific Islander and American Indian populations, these may also prove to be good target populations to screen.
