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Transfusion Service

(P-TS-47) Evaluation of non-specific reactivity rates across two automated immunohematology testing platforms with assessment of subsequent specific alloantibody development

Sunday, October 20, 2024
12:00 PM - 1:00 PM  
Background/Case Studies: Automated testing platforms such as solid-phase assays and gel microtubes are commonly used for pretransfusion testing, but are also prone to nonspecific reactivities (NSP) compared to tube testing. This study aims to characterize the features of NSPs in a solid-phase and two gel-based platforms and how frequently NSPs in these platforms precede specific antibody detection.

Study

Design/Methods: All antibody screens and identification panels performed at a large academic medical center between 5/2021–4/2023 were analyzed with IRB approval. Testing platform, results such as antibody identification, strength of reactivity for every reagent cell, and RBC antibody history were extracted from the electronic medical record and laboratory information system. For panels with NSPs identified on an automated platform, the strength of reactivity of cells were collected as 0, weak+ (recorded as 0.5), 1+, 2+, 3+, 4+. The differences in strength of reactivity for the testing platforms were compared with the Kruskal-Wallis test (P< 0.05 was considered statistically significant).

Results/Findings:

During the 24-month study period, a total of 156,247 antibody screens were performed with 5,491 positive screens, and NSP identified in 259 patients. Amongst those with specificity, passive anti-D was the most frequent (840, 21.6%) while anti-E was the most common alloantibody (477, 12.2%).

 

Between 5/2021–4/2022, solid-phase (Immucor, Norcross, GA) was the primary automated system, and NSP were identified in 116 screens out of 2692 positive results in a total of 78,262 screens performed. Between 5/2022–4/2023, automated gel (Grifols, Los Angeles, CA) was the primary automated system, and NSP were identified in 123 screens out of 2799 positive screens in a total of 77,985 screens performed. During the 24-month period, supplementary testing with an alternative manual gel platform (Ortho Diagnostics, Raritan, NJ) was performed concurrently as needed, and NSPs were also found in these manual gel screens 64 times.

 

The mean strength of reactivity for NSP was 1.72 in solid phase, 0.7 in automated gel, and 0.7 in manual gel. The Kruskal-Wallis analysis showed the strength of reactivity was statistically different between the three platforms with mean rank scores of 2211, 1739, and 2044 respectively (P< 0.001).

 

There were 9 panels where NSP correlated with a new alloantibody detected later (Figure A). The mean and median strength of reactivity was 1.0.

Conclusions: NSPs infrequently signal the development of a new alloantibody per this retrospective analysis. Amongst non-specific reactions, solid phase platforms show stronger reactivity by agglutination for NSPs, while automated gel shows a slightly higher rate of non-specific detection overall.