Study shows success in disproving sulfonamide allergies | Journalist VUMC


by Nancy Humphrey

Self-reported antibiotic allergies that end up in a patient’s electronic health record are common, but can lead to poorer patient outcomes.

In immunocompromised patients, antibiotic allergies may limit the antibiotic options they need to take prophylactically or therapeutically. In many cases, since alternative medications are more expensive, this is a limitation that can end up costing the patient and the healthcare system thousands of additional dollars every year.

A study from Vanderbilt University Medical Center published in Transplant infectious diseases shows that physicians can successfully identify and refute allergies to low-risk sulfonamide antibiotics (trimethoprim/sulfamethoxazole) using oral antibiotic challenge in consenting patients prior to solid organ transplantation.

Solid organ and stem cell transplant recipients are at higher risk of infection-related complications due to their immunocompromised status. Due to multiple factors, the transplant population is also susceptible to recurrent infections requiring antibiotics for treatment and prophylaxis.

Cosby Stone Jr., MD, MPH

“Pre-transplant antibiotic allergy demarcation is safe, of great value, and should definitely be considered in the pre-transplant evaluation period,” said Cosby Stone Jr., MD, MPH, assistant professor of medicine in the Division of Allergy, Pulmonary and Critical Care Medicine. Stone is the author of the study led by Chelsea Gorsline, MD, an infectious disease transplant fellow who recently left VUMC after completing her fellowship.

“After a transplant, these patients will usually take trimethoprim/sulfamethoxazole (the most commonly prescribed sulfa antibiotic) to prevent infections. Being able to take the older, more effective and cheaper drug instead of the more expensive and less effective alternatives will hopefully improve their treatment results and save them money for the rest of their lives.

The retrospective analysis included 27 patients with an antibiotic allergy label who underwent evaluation for solid organ or stem cell transplant between 2015 and 2020. The majority were being evaluated for lung transplants . All patients included in the review had at least one suppressed antibiotic allergy, suggesting that many self-reported antibiotic allergies were either inaccurately labeled or remained past their natural expiration date, said Stone.

Patients completed pre-transplant antibiotic markdown by VUMC’s Drug Allergy Clinic and were followed for six months. No side effects were reported over the six months, and patients saved up to $2,910 per patient during that time by avoiding the use of more expensive and less effective alternative antibiotics, Stone said.

To remove the label of a drug allergy, a person is ranked by risk based on their allergy history. People in the low-risk category can receive a single dose of antibiotic at the drug allergy clinic where they can be monitored for a reaction. Individuals at moderate or high risk for persistent allergy can be assessed by patch testing or stepped challenges (small doses before a dose that can be used in a typical treatment). “These are safe procedures. We do them regularly,” Stone said.

The study, which focused specifically on sulfonamide allergies due to its relevance in transplants, is part of a larger VUMC effort to suppress self-reported allergies to antibiotics, including penicillin, first-line antibiotic of choice to treat infections. Over the past two years, a testing program led by Stone, Elizabeth Phillips, MD, John A. Oates Professor of Clinical Research and Professor of Medicine, Department of Pharmacy and Vanderbilt Learning Healthcare System, has resulted in more 100 penicillin treatments for patients previously labeled as penicillin allergic. Research shows that up to 95% of labeled penicillin allergies, reported by 10-15% of the US population, may be inaccurate. The VUMC program also looked at allergies to cephalosporin antibiotics.

The current study on allergy delabeling in transplant patients paves the way for more research, Stone said.

“We are prioritizing transplant patients for antibiotic allergy evaluations because they will need the drugs soon,” he said. “Given the demonstrated success in this small cohort, this practice could be incorporated into routine pre-transplant protocols across all of our transplant teams and other institutions,” Stone said. However, this requires knowledge of the value and availability of the service by organ transplant teams and the availability of allergy services with relevant expertise.

“Although the service is readily available at our facility, less than 50% of infectious disease experts have ready access to allergists who can test their patients for drug allergies,” he said.

Stone said he would like to see this study lead to collaboration with other medical centers that offer transplants.

“We would really like to know what effect this has on the rate at which these patients get infections, which is a key indicator for transplant care,” he said. “And we would like to know if this type of available program improves any of the other key outcomes for transplant patients. Above all, we would love to partner with others who want to build their ability to unlabel drug allergies. We suspect that further evidence will confirm our suspicion that putting first-line antibiotics back on the table helps our patients achieve better outcomes and save money on their drug costs.


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