(P-TS-92) Pediatric and Young Adult ABO Titers Performed by Automated Testing Correlate with IgM and DTT-Treated IgG Tube Testing

Background/Case Studies: Antibody titers are commonly obtained for IgM and IgG titers of anti-A and anti-B for patients receiving solid organ transplants. Titers performed using a manual tube method can be prone to variation between technologists, making it difficult to fully assess changes in titers over time. Automated methods have been developed to reduce this testing error, though few studies evaluate testing in pediatrics or the role of dithiothreitol (DTT) treatment for IgG testing. This study evaluates automated testing compared to manual tube testing in a pediatric and young adult population using both IgM and IgG phases, including the use of DTT treatment.

Study

Design/Methods: Plasma samples collected in EDTA were aliquoted and treated with 0.01M DTT or phosphate buffered solution (PBS) control creating a 1:1 dilution. Aliquots were incubated at 37^oC for 30-45 minutes, then subsequently tested with Anti-A and/or Anti- B reagent antisera at immediate spin. After confirming that the IgM ABO antibody was destroyed in the DTT treated samples, isohemagglutinin titers were performed on both sample aliquots (DTT and PBS treated) using serial dilutions and testing for the expected ABO antibody at the IgG phase of reactivity. Samples were tested using both manual tube testing and the automated NEO Iris® (Werfen, Norcross, GA).

Results/Findings: A total of 37 plasma samples (52 titers) were tested for anti-A and anti-B titers for both IgM and IgG. Plasma was tested using deidentified discarded samples from individuals with an average age of 13.6 years and median age of 10 years (range 1-35 years, 70% < 18 years). Of these, 10 were type O, 11 type A, 11 type B, and 5 type AB. IgM titers were consistently lower in automated compared to manual testing. Of these, 24 (46%) were 1-2 dilutions lower, 27 (52%) were equivalent, and one was one dilution higher. IgG titers were performed using manual testing after addition of PBS or DTT treatment. PBS manual titers had no correlation to automated titers; however, treated manual titers were consistently lower than automated titers, with 26 (50%) titers being 1-2 dilutions higher with automated testing and 24 (46%) titers being equivalent (Table 1).

Conclusions: Titers in children and young adults were different between manual and automated testing for both IgM and IgG. IgM titers were lower with automated compared to manual testing within 1-2 dilutions. IgG titers did not correlate with PBS diluted samples, but when treated with DTT, automated testing showed consistently higher titers compared to manual testing. Automated testing can therefore be used in pediatrics and young adult testing after performing correlations to current testing and requires the use of DTT treatment when comparing IgG titers between manual and automated methods.