The authors cite one of our publications that the most common drugs encountered in our laboratory were cefotetan, ceftriaxone, piperacillin, and β-lactamase inhibitors (in that order). I should point out that such statistics change. For the period 2006–2010, we saw no cases associated with β-lactamase inhibitors, and the frequencies of occurrence were reversed for the other drugs (in the order piperacillin, ceftriaxone, and cefotetan). Several important lessons can be learned from this case report. In particular, piperacillin has several characteristics that differentiate it from other penicillins. First, although piperacillin will bind efficiently to red blood cells (RBCs), such in vitro–treated RBCs are not the target of choice for diagnostic testing. That is because a high percentage of the sera from patients without hemolytic anemia (HA) and healthy donors will react with the drug-treated RBCs. As opposed to precoating the cells with drug, the method of choice is to mix a patient's serum with piperacillin and untreated RBCs and observe for agglutination, lysis, and positive results in antiglobulin tests. Sera from patients and donors (no HA) that react with drug-coated RBCs do not react by this method. The other important lesson is that piperacillin-induced HA can mimic autoimmune HA and delayed hemolytic transfusion reactions (1, 2). The piperacillin antibody can even show blood group specificity (e.g., “auto” anti-e). As the authors point out, these reactions can be observed when piperacillin is not added in vitro (because there might be enough drug present in the patient's plasma) and incorrectly suggest an autoantibody. In piperacillin-induced HA, the reactions will cease 24–48 h after the drug is discontinued, whereas a true autoantibody will still react. Often, patients will be given steroid therapy for autoimmune HA, which will have little or no affect on the HA, whereas discontinuing the drug will lead to a hematologic remission.
Author Contributions: All authors confirmed they have contributed to the intellectual content of this paper and have met the following 3 requirements: (a) significant contributions to the conception and design, acquisition of data, or analysis and interpretation of data; (b) drafting or revising the article for intellectual content; and (c) final approval of the published article.
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Employment or Leadership: G. Garratty, American Red Cross.
Consultant or Advisory Role: None declared.
Stock Ownership: None declared.
Honoraria: None declared.
Research Funding: None declared.
Expert Testimony: None declared.
- Received for publication August 30, 2011.
- Accepted for publication September 6, 2011.
- © 2012 The American Association for Clinical Chemistry