Rochester, Minnesota—Penicillin allergy actually is rare, despite the frequency of reporting. In fact, according to a new article, less than 5% of patients who report a penicillin allergy will have a currently active clinically significant immunoglobulin E- or T cell-mediated hypersensitivity when appropriately tested.
The issue is especially significant in pregnancy, wrote Mayo Clinic–led researchers. “Penicillin is the agent of choice for intrapartum antibiotic prophylaxis to reduce the risk of group B streptococcus [GBS] early-onset disease in the newborn,” they noted. “Inaccurate penicillin allergy status may lead to inappropriate antibiotic use, as most alternative drugs are more expensive and broader spectrum than penicillin. Penicillin allergy testing has been found to be safe in pregnancy and cost-effective in other patient populations.”
Their study in PloS One sought to evaluate the cost-effectiveness of penicillin allergy testing and appropriate antibiotic treatment (i.e., test then treat strategy) compared with usual care among pregnant women.
To do that, the study team developed a decision tree. Its purpose is to evaluate the cost of providing appropriate care via a test-then-treat strategy for pregnant women who reported a penicillin allergy, compared with usual care.
The results indicated that, when using the test then treat strategy, the additional cost to ensure appropriate care for all pregnant women who reported a penicillin allergy was $1,122.38 per person. “Adopting a test then treat strategy increased the number of appropriate antibiotic use from 7,843/10,000 to 10,000/10,000 simulations,” the authors wrote.
“Our results show that a test then treat strategy for pregnant women who report a penicillin allergy is a good-value intervention,” the researcher pointed out.
The findings are important because penicillin allergy is the most commonly reported allergy in pregnant women. “The reported rate of unconfirmed penicillin allergy of about 8.0% in pregnant women is lower than commonly reported rates in outpatients using healthcare or other hospitalized populations,” the study explained. “In hospitalized patients, penicillin allergy is also the most commonly reported antibiotic allergy, occurring in 10% to 25% of patients.”
The authors argued that it is important to investigate claims of antibiotic allergies because, “when reported adverse reactions to antibiotics are not explored by prescribing providers, it often results in the use of alternative broader spectrum treatment than is required. This practice contributes to the overuse of broad-spectrum agents which has added to the emergence of multiple drug-resistant microbes.”
“An alternative antibiotic to penicillin includes first-generation cephalosporins such as cefazolin for women with a low-risk penicillin allergy,” the study advised. “In women with high-risk penicillin allergy or a positive allergy test, clindamycin is recommended; however, GBS isolates can be resistant to clindamycin and therefore susceptibility testing is necessary. When a GBS isolate is not susceptible to clindamycin, vancomycin is the only validated option for intrapartum prophylaxis in patients with a penicillin allergy. GBS is the most common infectious cause of morbidity and mortality in neonates. The primary risk factor for early-onset GBS infection in neonates is colonization of the maternal rectum or genital tract, and between 10% to 30% of women are colonized with GBS.”
Taking into account the significant morbidity and mortality associated with neonatal GBS infection, the CDC and American College of Obstetricians and Gynecologists (ACOG) recommended universal culture-based GBS screening for all prenatal patients aged between 36 0/7 and 37 6/7 weeks of gestation. “GBS remains susceptible to both penicillin and ampicillin, and penicillin is the treatment of choice for GBS infections and prophylaxis because of its low cost, effectiveness, and narrow antimicrobial spectrum,” according to the researchers. “For this reason, ACOG has recommended penicillin allergy testing for pregnant women who report a penicillin or amoxicillin allergy. This recommendation aligns with the American Academy of Allergy, Asthma and Immunology’s 2016 recommendation that penicillin allergy testing should be routinely performed on all patients with a listed allergy to penicillin, ampicillin, or amoxicillin.”
Past research has found penicillin allergy testing to be cost saving, with a net benefit ranging from $256 to $6,745 for inpatients and outpatients, respectively.
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