Drug-dependent antibody

[lab217]

We have recently experienced some patients that encountered a suspected drug induced hemolytic episode. The offending antibiotic seems to be piperacillin. Does anyone have any policies or procedures in place, either through blood bank, pharmacy or another department, that helps in early detection (ie daily hemoglobins, DAT's). Any suggestions would be greatly appreciated!

[Malcolm Needs ☆]

I'll try to get my friend Robert Stamps, who is the UK authority on drug-induced AIHA to answer this one. I think he's a member of this site. If not, I'll twist his arm to become a member!!!!

[lab217]

I truly appreciate that Malcolm! I would rather be proactive than reactive, if at all possible!

[Malcolm Needs ☆]

No problem. I've emailed him and asked, ever so politely, to get his finger out. Sadly, he's gone home from work tonight, and I don't know his private email address. I'll work on that!!!!!

[Bobajob]

There is no effective proactive measures you can take other than standard hemolysis checks ie LDH, haptoglobins if the Hb falls unexpectedly. Positive DAT's are common in patients with infections Piperacillin induced AIH is rare considering how commonly the drug is used. As with other penicillins the patient usually has to be on intravenous doses of the drug for at least a week before the DAT becomes positive (usually IgG). Even then the majority of patients do not hemolyse. The investigation of an hemolysing patient is relatively straightfoward as the drug (10mg/mL solution in PBS) readily coats red cells at 37C though raising the pH increases the uptake. Testing the patients serum and an eluate from the patients red cells with the drug treated cells by IAT usually gives convincing results. You would expect the eluate to be negative by IAT with untreated red cells.

[GinaL]

There is no effective proactive measures you can take other than standard hemolysis checks ie LDH, haptoglobins if the Hb falls unexpectedly. Positive DAT's are common in patients with infections Piperacillin induced AIH is rare considering how commonly the drug is used. As with other penicillins the patient usually has to be on intravenous doses of the drug for at least a week before the DAT becomes positive (usually IgG). Even then the majority of patients do not hemolyse. The investigation of an hemolysing patient is relatively straightfoward as the drug (10mg/mL solution in PBS) readily coats red cells at 37C though raising the pH increases the uptake. Testing the patients serum and an eluate from the patients red cells with the drug treated cells by IAT usually gives convincing results. You would expect the eluate to be negative by IAT with untreated red cells.

Drug-induced immnune hemolytic anemia is uncommon, but piperacillin is now the top contender of all the drug antibody investigations we perform in Dr. George Garratty's research lab at the American Red Cross, Southern California Region. Ceftriaxone and cefotetan are also high on our list. Piperacillin, although it is a semi-synthetic penicillin is unlike penicillin G in both the clinical presentation and in the serology. Piperacillin is often given in combination with tazobactam, a beta lactamase inhibitor, and is commonly given to patients with cystic fibrosis for lung infections. Patients who develop anti-piperacillin often have prior exposure to the drug. Also unlike with penicillin, intravascular hemolysis can be seen and the hemoglobin can drop dramatically. Fatalities have been reported. Unfortunately, we cannot predict which patients will or will not develop anti-piperacillin. Monitoring the hemobglobin is the best initial indicator, then following up with the other typical indicators of hemolysis (indirect bili, LDH, haptoglobin, evaluating peripheral blood smear). A direct antiglobulin test should then follow suspected hemolysis to determine if it is immune-mediated.

A significant finding with piperacillin antibodies is that while the patient is still receiving the drug (it is intravenous), the serology can mimic warm autoantibodies, and often with anti-e specificity. One-to two days after the drug is stopped, however, this plasma reactivity disappears. We believe this reactivity is caused by circulating drug (i.e., no in vitro drug is needed). And to baffle this serologist, we have even seen reactive eluates is some patients with this phenomenom. We have even seen some patients who have mistakenly been treated for warm autoimmune hemolytic anemia (e.g. with steroids) based primarily on the serology. Once the drug is stopped the hemolysis subsides.

Testing for antibodies to piperacillin is performed by adding a solution of the drug to serum and untreated RBCs (we also test enzyme-treated RBCs). Piperacillin does bind readily to RBCs so testing can be performed with piperacillin-treated RBCs, but we have found that plasma from blood donors and random patients can directly agglutinate piperacillin-treated RBCs, so we do not recommend this method in order to avoid misinterpretation (false positive result). Piperacillin antibodies do not have high titers so testing a dilution of the serum to get around this problem is not advised.

So, in addition to a dropping hemoglobin, a serologic clue is a new warm autoantibody in a patient whose initial clinical presentation is not warm autoimmune hemolytic anemia! If the eluate is reactive, it may react weaker than the plasma.

Gina Leger

[Malcolm Needs ☆]

Thanks for that fantastically informative post Gina.