Two cases of immune haemolytic anaemia, associated with anti-piperacillin, detected by the ‘immune complex’ method

Background and Objectives Sera containing antibodies to penicillin and penicillin-related drugs are typically thought to react with drug-coated red blood cells (RBCs) (drug adsorption method), but not when the sera are added to drug and RBCs in the same tube (‘immune complex’ method). Two cases of immune haemolytic anaemia caused by anti-piperacillin have been previously described. Serological details were given in only one patient. In that subject, the antibody was immunoglobulin (Ig)M + IgG and reacted by both the drug adsorption and ‘immune complex’ methods. Materials and Methods Two patients with cystic fibrosis developed positive direct antiglobulin tests (DATs) and haemolytic anaemia after 11–12 days of piperacillin therapy. Serological studies were performed with piperacillin, Zosyn (piperacillin + tazobactam) and penicillin by using the drug adsorption and ‘immune complex’ methods. Results The first patient's serum contained an IgG, complement-activating anti-piperacillin that reacted by the ‘immune complex’ method only. The second patient's IgM + IgG, complement-activating anti-piperacillin reacted by the ‘immune complex’ method and agglutinated piperacillin-treated RBCs. An eluate from the patient's RBCs reacted weakly with all RBCs tested without the presence of drug. This patient had evidence of intravascular haemolysis and died. Conclusions We describe the third and fourth examples of immune haemolytic anaemia caused by anti-piperacillin; one was associated with fatal haemolytic anaemia. As piperacillin is commonly used in the treatment of cystic fibrosis, anti-piperacillin should be considered whenever patients with cystic fibrosis develop haemolytic anaemia and/or positive DATs.