FCAAIA Notes: Of all the medications out there, the one for which we have the best data about how to interpret testing is penicillin. If your testing to penicillin and a metabolite of penicillin (Pre-Pen®) is negative, there is up to a 95% chance you do not have an immediate-type allergy to penicillin, even if you have a strong history suggesting allergy). The several percent “false-negative” are probably allergic to other metabolites (minor determinant mixture, MDM). Patients who had severe allergic reactions to penicillin are sometimes allergic to MDM, creating a bit of a quandary. So, we often eliminate that last 5+% by doing an observed in-office challenge to penicillin in patients with negative skin testing.
MDM is not commercially available yet. Studies show that if testing is also negative to MDM, the risk of current penicillin allergy is for all intents and purposes zero. The Food and Drug Administration has held up approval of MDM for testing, although no one I know has ANY idea what its motivation is.
See the article “Prescribers Have Poor Understanding of Penicillin Allergy” also posted today.
(Source: http://www.medscape.com/viewarticle/871833?src=WNL_confwrap_161124_MSCPEDIT&uac=112079PK Nov.24, 2016. For Medscape articles: User name: FCAAIA, Password: Allergies)
Patients with a penicillin allergy indication on their electronic medical record test negative for penicillin allergy nearly 90% of the time, new research shows.
Testing these patients can dramatically reduce the use of broad-spectrum antibiotics in hospitals.
“We were able to avoid prescribing vancomycin, fluoroquinolones, clindamycin, carbapenems, and aztreonam in a substantial number of cases, both while patients were in the hospital and at discharge,” said Justin Chen, MD, from the University of Texas Southwestern Medical Center in Dallas.
“We think our protocol could be useful at any institution that is interested in improving infection outcomes,” he told Medscape Medical News.
Dr Chen described the team approach to tackling penicillin allergy screening, piloted at the Parkland Health and Hospital System in Dallas, here at the American College of Allergy, Asthma & Immunology 2016 Annual Scientific Meeting.
During an 18-month period, a dedicated allergy pharmacist looked over charts flagged by an algorithm developed to pinpoint patients who might need screening. The algorithm looked for patients coming into the hospital who reported a penicillin allergy and prioritized them for testing on the basis of the antibiotics they were receiving and whether they were at high risk for infection and would likely need antibiotics in future.
Of the 252 patients prioritized for testing, a large number had high-risk conditions — 90 patients had diabetes, 36 had HIV, 24 had malignancy, and 13 had immunosuppression.
Penicillin allergy testing was performed with a PRE-PEN skin test antigen, penicillin G skin prick and intradermal test, followed by oral amoxicillin 500 mg. Of the 252 patients tested, 223 (88.5%) were found not to be allergic.
“After a negative test, we educate the patient on the results” and explain to them that they can take penicillin now and into the future, said Dr Chen.
In addition, after a negative test, the penicillin allergy label was removed from the patient’s record. Care teams were then notified of results. In 77 of the 223 cases (34%), patients were switched from alternative beta-lactams to a penicillin or cephalosporin, which reduced the use of vancomycin by 34%, clindamycin by 61%, aztreonam by 68%, carbapenems by 50%, and fluoroquinolones by 36%.
The researchers estimated that this prevented 504 inpatient days and 648 outpatient days on alternative agents.
In addition, five patients (2%) were cleared of their allergy when researchers looked closely at their health record and found previous use of penicillin, despite a label of a penicillin allergy.
“The majority of patients report remote reaction histories, but the label sticks with them throughout their lives despite true allergy resolving with time,” Dr Chen explained. “There’s a misconception about the natural course of drug allergy.”
Simply having the label of penicillin allergy on an electronic medical record is associated with higher rates of infection with Clostridium difficile, methicillin-resistant Staphylococcus aureus, and vancomycin-resistant enterococci, and increased rates of hospitalization. “If we can clarify the allergy status and eliminate some of these complications, that’s the biggest benefit,” he said.
In the study cohort, 19 patients (7.5%) did not complete testing and five (1.9%) tested positive. The patients who tested positive had a history of urticaria or angioedema skin reaction with penicillin, associated with itching, which usually resolves within 24 hours, Dr Chen said.
One patient reported having had a reaction in the previous year, two patients in the previous 5 to 9 years, one patient in the previous 10 to 19 years, and one patient in the previous 20 years.
“In our institution, we’re hoping to implement a similar protocol,” said Connie Lin, MD, a fellow at the University of California, Los Angeles. She noted that as well as being important for antimicrobial stewardship, it is also beneficial for cost-effectiveness, because some beta-lactam alternatives are more expensive. “It’s good to know that someone’s already done this successfully. This is a really good model,” she said.
According to the latest guidelines from the Infectious Diseases Society of America and the Society for Healthcare Epidemiology of America, allergy testing is recommended to improve antimicrobial stewardship, but few hospitals have allergist-directed protocols dedicated to this.
“It’s going to take a concerted effort on the part of allergists and all of our colleagues to improve understanding of penicillin allergy testing and how it might offer benefits for antimicrobial stewardship,” Dr Chen explained. “Our model could make a big difference.”