Our fellow, Nathan Shively, recently presented “Impact of Reported Beta-Lactam Allergy on Inpatient Outcomes: A Multicenter Prospective Cohort Study,” published in Clinical Infectious Diseases, at journal club on October 31, 2016. This was a trainee-led quality improvement initiative at 3 academic hospitals in Canada with the hypothesis that receipt of alternative therapy when a beta-lactam agent was the preferred therapy would lead to worse clinical outcomes. Prior studies have evaluated this in retrospective fashion, with findings that patients labeled with “penicillin allergy” have longer length of stay, are treated with more broad spectrum antibiotics, and have more C diff, MRSA, and VRE.

The investigators included patients seen on the Infectious Disease consult service between April 2014 and January 2015, and prospectively collected a characterization of any prior beta-lactam allergy, as well as the preferred antibiotic therapy and the antibiotic therapy that was initially chosen, among other variables. The primary outcome was treatment-related adverse events, a composite outcome comprised of acute kidney injury while on treatment, C diff infection within 3 months of treatment, drug-related adverse reaction requiring discontinuation, and readmission for the same infection. Ultimately 507 patients were included for analysis.

They found that 95 (19%) of patients reported a beta-lactam allergy. In this group, there were 25 patients for whom beta-lactam therapy was the preferred therapy and it was not received due to allergy history. This group was found to have a significantly higher risk of adverse events (odds ratio 3.18 in the multivariable analysis, CI 1.28 – 7.89) compared to patients without reported allergy, with the composite outcome being driven primarily by drug reaction and readmission for the same infection.

This study adds to the existing evidence that the label of “penicillin allergy” is not benign, as it can potentially lead to patients receiving inferior and/or more harmful treatments when beta-lactams are the preferred therapy.

Discussion focused on the importance of an accurate allergy history as a component of antimicrobial stewardship, as this in many patients will reveal a history of a non-IgE-mediated reaction, in which case proceeding with beta-lactam therapy is acceptable. We also discussed the potential utility of inpatient beta-lactam skin testing if concerns remains. While this is not currently available at all center, some have implimented this safely and successfully. While further investigation is needed, the available literature suggests that this may be a strategy that could improve outcomes and reduce costs.