ABO Antibody Titer Testing Harmonization in Korea: A 5-Year Analysis of External Quality Control Data.

Current ABO titration methods lack standardization and harmonization. We analyzed the consistency of ABO antibody titer testing among Korean laboratories and discussed future directions for standardization by analyzing external quality control data collected by the Korean Association of External Quality Assessment Service over 5 yrs (2019-2023). The analysis included the number of participating institutions and methods, as well as the proportion of acceptable results. To compare column agglutination technology (CAT) and tube methods, we created a normalized variable: ([log₂ titer of laboratory test result]-[mean of log₂ titer for the peer group]). The number of participating institutions and methods increased over time. The use of CAT methods expanded, whereas that of tube methods declined. The proportion of acceptable results ranged from 84.0% to 100%, with no significant differences between CAT and tube methods. An F-test revealed no significant variance differences among institutions using these methods. Tube methods demonstrated lower variance in anti-human globulin testing, and room temperature tube methods exhibited lower variance than that of CAT methods. Domestic laboratories demonstrated highquality performance in ABO antibody titer testing, with no significant differences in acceptable result rates or variance across methods. Continuous efforts toward standardization remain essential.