(P-TS-40) Detection of a and B Antigens by Gel and Tube in Cord Blood Samples

Background/Case Studies: Newborn cord blood testing for ABORh is routinely performed by our Transfusion Laboratory using gel methodology. If an ABO discrepancy is noted, the specimen is referred to our Immunohematology Reference Laboratory (IRL) for resolution by test tube. The goal of this study was to determine the discrepancy rate in cord blood ABORh testing by blood type and to establish any relationship in discrepancies with newborn gestational age (GA).

Study

Design/Methods: Data was collected on cord blood samples tested for ABORh in 2024. All samples were initially tested using a manual gel method (Ortho MTS™). Samples with discrepancies due to a mixed-field appearance by gel testing (GT) were washed several times and tested using the manual tube testing (TT) method by the IRL. If the mixed field remained, the ABORh was either interpreted as invalid, or in cases where Rh Immune Globulin administration was pending, a heel stick was collected and separately tested to resolve the discrepancy. GA at the time of sample collection was calculated and compared between testing methodology groups using ANOVA.

Results/Findings: A total of 1168 cord blood samples were tested for ABORh. All blood group O samples were resulted by GT while only 82% blood group A, 41% of blood group B, and 0% of blood group AB were resulted by GT (Table 1).

Conclusions: Initial GT gave valid ABORh interpretations for all group O cord blood samples tested. Discrepancies were found in 18% of blood group A, 59% of blood group B, and 100% of blood group AB sample with the average GA of blood group A, B, and AB samples resulted by GT or TT being 1 week greater than those that could not be resulted with either methodology. These results suggest that GA may need to be considered when developing processes for newborn cord blood ABO testing.