The University of Kansas Health System Kansas City, Kansas, United States
Background/Case Studies: Antibody detection and identification is a central component of blood bank management. Although the conventional tube test (CTT) serves as the reference standard, most large institutions utilize a semi-automated platform using column agglutination (CAT) or a solid-phase red cell adherence assay (SPRCA). All three methods generally demonstrate comparable sensitivity and specificity, and each may be employed as the primary screening method or as a supplemental test for inconclusive cases.
Study
Design/Methods: Four cases are reported from a retroactive review of available clinical and laboratory data to highlight discrepant antibody identification. At our institution SPRCA is the primary screening method, CAT is the major supplemental method, and CTT serves as a tertiary method.
Results/Findings: Four patients had positive SPRCA antibody screening with discrepant supplemental testing (see Table 1). The first patient received chronic red cell exchange for sickle cell disease with pre-exchange SPRCA screening showing weak pan-reactivity consistent with a history of cold autoantibody. Follow up CAT was negative, and exchange was completed. The patient returned with signs of delayed hemolysis. Repeat SPRCA testing showed similar results and CTT was negative at all phases. Additional SPRCA and eluate testing indicated anti-e specificity, and genotyping confirmed a partial e and negative HrB antigen. The second patient had Crohn’s disease and was evaluated for severe anemia. Stat SPRCA screening showed weak reactivity and CAT was negative. An expanded SPRCA panel confirmed a new anti-f antibody. The third patient had relapsed acute myeloid leukemia with pancytopenia. Weak reactivity by SPRCA was followed by negative CAT and CTT. Additional SPRCA testing confirmed a new anti-Jkb antibody. The fourth patient required ECMO for cardiogenic shock and the fifth SPRCA antibody screen following admission showed weak reactivity, but negative results by CAT and CTT. An SPRCA panel identified a new anti-Jka antibody. Conclusions: The SPRCA may be more sensitive in the detection of antibodies against Rh and Kidd antigens. Additional evidence is needed to compare the diagnostic accuracy of available serologic methods to inform laboratory choice of antibody screening methods. Detection of clinically significant antibodies with weak in vitro reactivity is essential to patient blood management.
Importance of research: Consideration of antibody identification methodology is multifactorial, including laboratory staffing, space, and experience, among others. Expected patterns of non-specific reactivity may lead to misinterpretation in the context of negative supplemental testing. The reported cases demonstrate situations in which clinically significant antibodies were detected by SPRCA testing, and alternative methodologies alone would have been insufficient to prevent potentially fatal transfusions.
