Misidentification of anti-Vel due to inappropriate use of prewarming and adsorption techniques

Two units of red blood cells (RBCs) were ordered for a 44-year-old Caucasian woman with renal failure and cancer. Pretransfnsion testing performed at the regional reference laboratory had revealed the presence of an antibody reactive with all cells at the indirect antiglobulin test but apparently nonreactive by a prewarmed IAT. The patient's RBCs were direct antiglobulin test negative. Adsorption of the serum with rabbit erythrocyte stroma or with allogeneic RBCs at 4 degrees C reduced the reactivity at the IAT. The patient was transfused with two units of washed RBCs and died 6 to 8 hours later. Retrospective testing in our laboratory detected anti-Vel in both pretransfusion and posttransfusion samples. The pretransfnsion serum was hemolytic when tested io LISS or with papain-treated RBCs. Weak reactivity (I+) was observed at the IAT. EDTA-treated serum (to prevent C'-mediated hemolysis) was strongly reactive (3+s) with Vel+ RBCs but compatible with 10 examples of Vel- RBCs. Adsorptions with rabbit RBCs did not affect reactivity. Pretransfnsion RBCs were nonreactive with three examples of anti- Vel at the IAT. The posttranshision serum was grossly hemolyzed and anti-Vel was demonstrable, although weaker than in the pre- transfusion sample. The antibody was subclassed as IgG1 and IgG3. In this case, the use of a prewarming technique precluded detection of hemolysis caused by the antibody prior to the IAT. This case stresses the importance of antibody identification and the correct use of such techniques as prewarming and adsorptions.