(P-IG-33) Prevalence and Classification of Red Blood Cell Antibodies: A 20-Year Retrospective Study at an Academic Medical Center

Background/Case Studies: The prevalence and classification of antibodies, including autoantibodies and alloantibodies, are critical for understanding immunohematology. This study aims to analyze a comprehensive dataset from an academic medical center covering the years 2005 to 2025, focusing on the prevalence of various antibody types, including warm and cold autoantibodies, reagent-specific antibodies, high-titer low-avidity antibodies, and alloantibodies.

Study

Design/Methods: A retrospective analysis was conducted on a dataset containing 1,039,253 antibody screen results and 28,443 antibody identification tests performed at Stanford Health Care (SHC) over a 20-year period. The dataset was categorized into autoantibodies (warm and cold), reagent-specific antibodies, high-titer low-avidity antibodies, inconclusive antibodies, and alloantibodies. Frequencies for each antibody classification were calculated to determine their prevalence.

Results/Findings: The overall positive antibody screen rate was approximately 3.4%, with a total of 35,898 positive antibody screens identified from the dataset. The analysis revealed that total autoantibodies accounted for 3,340 tests, representing approximately 11.74% of the total antibody tests. Within this category, warm autoantibodies totaled 2,433, while cold autoantibodies accounted for 907. Reagent-specific antibodies and high-titer low-avidity antibodies were minimal, comprising 0.25% (71 tests) and 0.13% (36 tests), respectively. Inconclusive antibodies represented 8.57% (2,438 tests) of the total. Notably, the total number of identified alloantibodies was significantly higher, with 22,558 tests, representing approximately 79.26% of the total antibody tests conducted. Among the identified alloantibodies, the most prevalent were anti-D (2,618, 9.20%) and anti-E (2,727, 9.59%).

Conclusions: This 20-year study highlights the significant prevalence of alloantibodies in an academic medical center, underscoring their importance in transfusion practices. While less prevalent, autoantibodies still represent a notable portion of the testing. The findings emphasize the need for ongoing monitoring and tailored transfusion strategies to improve patient outcomes. This study adds to the existing literature on antibody prevalence with a larger testing cohort to support appropriate reference testing and clinical management of patients with positive antibody screens.