University of Virginia Charlottesville, Virginia, United States
Background/Case Studies: An elution is performed when a direct antiglobulin test (DAT) is positive for IgG to evaluate for a red cell antibody. The AABB Technical Manual states that the eluate is likely to be nonreactive when the only coating protein is complement, thus many C3-only positive DATs do not warrant an elution study. Here, we present a case of C3-only positive DAT and how performing an elution aided the diagnosis of passenger lymphocyte syndrome (PLS).
Study
Design/Methods: Clinical and laboratory data were extracted via chart review. ABO/RhD typing, antibody screen, cold agglutinin screen (CAS), a DAT and eluate were performed via tube testing.
Results/Findings: 77-year-old man with a history of end stage renal disease requiring a minor ABO-incompatible deceased donor kidney transplant (DDKT) (recipient blood type AB; donor blood type A). On the day of kidney transplantation, the patient had a negative type and screen and a normal hemoglobin. He did not receive transfusions recently. Over the next 2 weeks, his hemoglobin gradually downtrended, without evidence of bleeding. On day 17 post-transplant, his hemoglobin was 6.8, with elevated LDH, undetectable haptoglobin and elevated unconjugated bilirubin, consistent with hemolytic anemia.
A repeat blood bank workup was performed, confirming the patient as type AB. The antibody screen was negative. The DAT was negative for IgG but positive for C3. CAS was negative. Given the strong suspicion for immune-mediated hemolysis, an elution was requested. The eluate initially tested negative against a panel of 13 donor red cells to rule out alloantibodies but upon recognition that the patient received a minor ABO-incompatible DDKT, the eluate was retested using A1 and B red cells. The eluate showed 1+ reactivity with B cells, negative with A1 cells. The titer of the eluate anti-B was 1.
Given the history of a minor ABO-incompatible DDKT, hemolytic anemia and the presence of anti-B on the recipient’s RBCs, a diagnosis of PLS was made. A stipulation was placed for the patient to receive type A RBCs and type AB plasma and platelets to avoid transfusion of isoagglutinins that may exacerbate hemolysis. The patient received two units of type A RBC transfusions and hemoglobin normalized after 4 weeks.
Conclusions: While an elution is always recommended when DAT is positive for IgG, the decision to perform it when only C3 is positive depends on the clinical context. This case highlights the need to review patients’ clinical history. Appropriate scenarios to perform an eluate include hemolysis in the setting of a recent transfusion, or a minor ABO-incompatible solid organ or stem cell transplantation. In the latter cases, an eluate against A1 and B cells may help determine if anti-A/B antibodies are the underlying cause of hemolysis. PLS is a self-limited condition and rapid diagnosis can help avoid unnecessary treatment.
