Patients with reported penicillin allergies are significantly more likely to develop surgical site infections, according to a study conducted at Massachusetts General Hospital in Boston.

With new evidence reporting 90%-99% of patients with a reported allergy are not actually allergic, conducting a preoperative allergy test could improve treatment choice and decrease the risk of SSI, as well as the notable financial burden associated with it. Thus, “systematic, preoperative penicillin allergy evaluations in surgical patients may not only improve antibiotic choice but also decrease SSI risk,” according to Kimberly Blumenthal, MD, the quality director for the department of allergy and immunology at Massachusetts General Hospital, and her fellow investigators.

Their retrospective study included 8,385 patients admitted to Massachusetts General Hospital during 2010-2014. The average age was 64 years, the majority were white (85%), and 22.9% of patients in the study were diagnosed with cardiovascular disease.

Surgeries performed were hip arthroplasty, knee arthroplasty, hysterectomy, colon surgery, or coronary artery bypass grafting.

Of the patients studied, 922 (11%) reported a penicillin allergy; most had minor reactions, such as rashes (37.5%) or urticaria (18%). “Only 5 reactions to penicillin represented contraindications to receiving a beta-lactam; the vast majority of patients would have tolerated first-line recommended cephalosporin prophylaxis had allergy evaluation been pursued,“ according to Dr. Blumenthal and her colleagues.

Overall, a total of 241 (2.7%) patients contracted an SSI. In a multivariate analysis, patients who had reported a penicillin allergy were 50% more likely to develop an SSI than those who had no reported allergy (adjusted odds ratio, 1.5; P = .04).

Risk may even be higher than 50% in the general health care population because this health center has a relatively low rate of SSIs, compared with many other hospitals, Dr. Blumenthal and her fellow investigators stated.

The increased risk primarily concerns the treatment used because those with a reported allergy were more likely than those without the allergy to be given clindamycin (48.8% vs. 3.1%, respectively), vancomycin (34.7% vs. 3.3%), gentamicin (24% vs. 2.8%), or fluoroquinolones (6.8% vs. 1.3%) instead of the most commonly used antibiotic, cefazolin (12.2% vs. 92.4%).

Patients given antibiotics other than cefazolin were usually given treatment outside of the perioperative window, which could severely increase the likelihood for developing an SSI, according to investigators. Of patients given vancomycin, 97.5% did not receive their treatment in the recommended time frame, compared with 1.7% of those given cefazolin.

“Increased odds of SSI among patients reporting a penicillin allergy in this cohort was entirely due to the use of beta-lactam–alternative perioperative antibiotics,” wrote to Dr. Blumenthal and her colleagues. “Patients with reported penicillin allergy in this study were not only less likely to receive the most effective perioperative antibiotic, they were also less likely to receive prophylaxis in the recommended time frame for optimal tissue concentration.”

While allergy assessments before surgery are currently recommended, there are no specifically outlined methods for these evaluations, which leads many providers to take what has been deemed the safer route of giving patients beta-lactam–alternative antibiotics instead, Dr. Blumenthal and her colleagues suggested.

The research was supported by the National Institutes of Health, and the investigators reported having no relevant conflicts.

SOURCE: Blumenthal K et al. Clin Infect Dis. 2018 Jan 18;66(3):329-36 .