Successful outpatient penicillin allergy testing with a low incidence of anaphylaxis during pregnancy demonstrates the feasibility of performing allergy testing in the outpatient setting, reported Nerlyne Desravines, MD, of the University of North Carolina, Chapel Hill, and colleagues.
In a prospective cohort study of 74 pregnant patients with previous self reports of penicillin allergy, Dr. Desravines and colleagues sought to determine the feasibility, acceptability, and safety of performing penicillin allergy testing in an outpatient setting. Patients included in the study were aged 18-55 years with gestational age between 14 and 36 weeks and planned delivery within the University of North Carolina heath care system receiving care between March 2019 and March 2020.
Of the 74 women enrolled to participate, 24 failed to present for testing, including some citing scheduling conflicts or fear of adverse reactions. Only 46 of the remaining 50 successfully completed testing; 4 patients were scheduled for testing but unable to participate because of COVID-19 restrictions.
Insurance status may affect participation in testing
Those who had public insurance were less likely to complete testing; those who completed testing were significantly more likely to be married and carry private insurance.
Fully 52% of the 46 women who completed testing were in the second trimester. The majority (85%) experienced their initial penicillin allergy reaction more than 10 years earlier.
Ultimately, 43 of the 46 women (93%) received a negative test result despite previous self reports of severe allergic reaction. Two of the three confirmed with penicillin allergy failed the 10% oral drug challenge; the other tested positive for penicillin G on intradermal testing. The two women who were found to have severe penicillin allergy experienced coughing, chest tightening, and skin and oropharynx pruritus within 30 minutes after their 10% amoxicillin drug challenge; they also experienced vomiting at 1 and 2 hours post ingestion. Following intramuscular injection of epinephrine, oral cetirizine with periodic vital sign measures, and albuterol updraft in one patient with a history of well controlled asthma, symptom resolution was achieved and both women were discharged without the need for further care.
The systemic reactions observed in just 4% of the study population is lower than normally reported in the general population, suggesting that the study sample size may underestimate the actual prevalence of systemic reactions, the authors noted. “The primary factor in safely conducting allergy testing in pregnancy is an outpatient facility that is appropriately outfitted with trained personnel and medications for possible serious reactions,” they added.
Noteworthy is the allergy testing protocol used by Dr. Desravines and colleagues in this study. Their graded oral drug challenge has not been used in previous studies of outpatient penicillin testing in pregnancy. Two of the three participants with positive test results had penicillin allergy confirmed following reaction to the first step (10% dose) of oral challenge to amoxicillin.
Prevalence of systemic reactions may be higher than expected
The authors cited ease of implementation in an obstetrics or allergy clinic as a strength of the study. One limitation is the observed rate of systemic reaction. The wide confidence interval observed indicates the rates of anaphylaxis may actually be as high as 15%, suggested the authors. The small sample size also limits the safety analysis for rare outcomes such as death.
Patient-reported barriers included time commitment for the testing visit. Rural women or those receiving prenatal care from health departments or community health centers were not able to be enrolled. Only one Spanish-speaking woman participated despite availability of bilingual staff and interpreters.
Such outpatient testing for those at greatest risk offers the opportunity to mitigate emerging drug resistance and should ideally take place preconception or at the time of initial allergic reaction, the authors advised. As emphasized in the latest Committee Opinion issued by the American College of Obstetricians and Gynecologists, obstetricians have a real opportunity to counsel patients preconception and postpartum regarding the benefits of penicillin allergy testing.
In a separate interview, Angela Martin, MD, assistant professor, maternal-fetal medicine, at University of Kansas, Kansas City, noted the large clinical implications of this study given that more than 90% of women undergoing allergy testing following self-reported penicillin allergy had a negative test result. “By performing allergy testing on appropriate candidates, as these authors have done, clinicians can treat infections and implement group B streptococcus prophylaxis with the narrowest spectrum antibiotic. This has potential to combat antibiotic resistance and may protect patients from harms caused by unnecessary broad-spectrum antibiotic use during pregnancy and beyond,” said Dr. Martin.
“It should be mentioned that 2 out of the 46 women tested (4%) had an anaphylactic reaction. This highlights the need to perform allergy testing in a qualified center capable of managing acute anaphylactic reactions should they occur,” she advised.
Dr. Desravines and colleagues, as well as Dr. Martin, had no conflicts of interest and no relevant financial disclosures.
SOURCE: Obstet Gynecol. 2021;137:56-61. doi: 10.1097/AOG.0000000000004213.