Wisconsin Diagnostic Laboratory Germantown, Wisconsin, United States
Background/Case Studies: While warm autoantibodies are most well-known for showing Rh specificity, specificities have been reported in the LW, KEL, JK, FY and DI blood systems. There have been documented cases of auto Jka antibodies in literature, some associated with autoimmune diseases and parvovirus. For autoantibodies with Jka specificity, there has been debate between if a true autoantibody can form or if it is just an alloantibody to a rare Jka subtype. With red cell genotyping becoming more accessible, autoantibodies can now be confirmed through molecular testing.
Study
Design/Methods: A primigravida female presented for prenatal testing at eight weeks gestation. Patient had no prior transfusions. The antibody screen was positive, and a panel was subsequently run on the analyzer (Echo Galileo, Werfen, Norcross, GA). Results indicated an anti-Jka was present, but select cells were needed. An auto control was run in parallel and was strongly positive. All other clinically significant antibodies were ruled out. The polyclonal DAT testing was positive with monoclonal testing showing positivity for both IgG and C3. The eluate was weakly reactive with all cells tested but showed stronger reactions on Jka positive cells. Antigen phenotyping was performed, and patient was Jka positive. Further investigation was performed to rule out any possible interference. As a precaution, a titer was done for the Jka and found to be less than one.
Results/Findings: The results suggested that the patient had developed an auto anti-Jka. This sample was then sent to an immunohematology reference lab for a molecular genotyping. Patient was found to have a predicted phenotype of Jk(a+b-). The antibody was ultimately resulted as a warm auto antibody with Jka specificity. Units that were computer crossmatched and unscreened for Jka were approved for transfusion by the medical director.
Conclusions: Although rare, it is important to be mindful of warm autoantibodies that may show specificity outside of the RH blood system as they can present a challenge to blood banks. The case demonstrates the importance of using molecular genotyping as a tool to confirm autoantibody identification. The results of a warm auto antibody can then be correlated with the patient’s condition and other lab results to look for evidence of hemolysis. Knowing the specificity of the warm antibody can allow for better selection of blood products in the event the patient is hemolyzing. In such cases, it may be necessary to select blood products that are antigen negative for the autoantibody’s specificity. Prenatal management of the patient would also be affected by the determination of an alloantibody versus an autoantibody.
