ABO antibody titres: a multisite comparative study of equivalency and reproducibility for automated solid-phase and haemagglutination titration, and manual dilution with gel column agglutination technology.

BACKGROUND: ABO antibody titres are important in many clinical decisions; however, much variability is observed in titre results. For reliable and reproducible titre results, automated ABO titration methods have been developed. In this 10-site study, we evaluated the equivalency of the automated ABO titration assays on the Galileo NEO, a fully automated blood bank analyzer (Immucor, Inc.) to manual titration with gel Column Agglutination Technology (CAT), as well as the reproducibility of both methods. MATERIALS AND METHODS: Ten different locations participated in this study. The equivalency study included 70 random samples at each site. The reproducibility study tested the same blinded 30-sample panel at each study site. Anti-A and anti-B IgM and IgG antibody titres were tested with both the automated and manual methods; additionally, dithiothreitol (DTT) treatment was used to inactivate IgM antibodies in the manual CAT method. RESULTS: The equivalency between CAT manual method and Galileo NEO automated titres at each site ranged from 38 to 88%; equivalency for each isotype was 66.2% for IgM, 60.6% for IgG, and 88.5% for DTT-treated IgG. The reproducibility study evaluated the titre variation of each sample obtained from the 10 sites. The average titre ranges (in doubling dilutions) for the automated and manual methods, respectively, were 2.15±1.0 and 4.03±1.8 for IgM, and 1.53±0.7 and 4.10±1.9 for IgG; for the manual DTT-treated IgG, the average titre range was 3.45±1.8 doubling dilutions. DISCUSSION: The results demonstrated that the Galileo NEO automated and manual CAT ABO titres are not equivalent. However, the study also demonstrated that titre reproducibility is enhanced with the Galileo NEO automated ABO titration assays relative to the manual CAT ABO titration method. Therefore, to improve management of patients receiving care across multiple institutions, our study supports the use of automated ABO titration.

ABO antibody titer performance characteristics and correlates between two automated platforms.

BACKGROUND: AABB standards require a policy for assessing transfusing ABO-incompatible plasma. After a fatal hemolytic event with incompatible plasma, our institution instituted platelet donor population titer method for ABO antibodies on the PK7300, with high-titer being defined as having isohemagglutinin titers greater than 256. We recently switched titering platforms to the Neo Iris and we seek to determine the equivalent isohemagglutinin high-titer cutoff on the Neo Iris as compared to the PK7300. METHODS: We measured the titers on 299 apheresis platelet donors and compared its performance characteristics at various cutoffs to the PK7300 reference standard. Discrepant results were manually diluted and retested on the Neo Galileo. Furthermore, since the Neo Iris is able to determine isotype and antigen specific titers, we also characterized these features in our donor population. RESULTS: IgM titer of 128 on the Neo Iris has better accuracy compared to the titer of 64 (94 % vs 93.6 %). Eleven of sixteen discordant results were in agreement with Neo Iris. Blood group O had the highest IgG antibody titers for both anti-A and anti-B (p = 8.4E-17 and 4.3E-09, respectively). Additionally, group O donors exhibited lower anti-A2 than anti-A1 IgG titers. DISCUSSION: The Neo Iris titer cut-off of 128 had the best overall accuracy and correlation with a 256 cut-off on our laboratory developed test on the PK7300 platform. Additionally, we found that group O donors had the highest titer antibodies, with typically higher IgG titers than IgM, and generally multiple dilution levels greater than other blood types.