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St. Joseph Mercy Health System

Antibiotic Use in Patients with Documented β-lactam Allergies: Impact of an Antibiotic Side-Chain-Based Cross-Reactivity Chart Combined With Enhanced Assessment

Curtis D. Collins, Pharm.D., M.S., BCIDP, FASHP; Kara Brockhaus, Pharm.D.; Shikha Polega, Pharm.D.; Nina West, Pharm.D.; Harvey L. Leo, M.D.; Tara Shankar, M.D.; Renee Bookal, Pharm.D.; Anurag N. Malani, M.D.

St. Joseph Mercy Health System
Ann Arbor, Michigan

β-lactam antibiotics with dissimilar R-group side chains are associated with low cross-reactivity.  The myths surrounding the incidence and reporting of β-lactam allergies, and the cross-reactivity of β-lactam antibiotics, may lead to use of non-β-lactam alternative antibiotics which have been associated with less efficacy (e.g., increased surgical site infections), and increased adverse events including Clostridioides difficile infections (CDI)).

A multi-disciplinary team at our hospital implemented an institutional approach for antibiotic management of patients with β-lactam allergies in October 2014.  Strategies included enhanced allergy assessment, and the use of an internally developed, literature-based, antibiotic side-chain-based cross-reactivity chart to guide prescribing.  Pharmacists actively intervened to assess for previous tolerance of β-lactams, ensure compliance with chart recommendations, and communicate with prescribers when warranted.   We describe the impact of the cross-reactivity chart in combination with enhanced allergy assessment, antimicrobial stewardship, and pharmacy processes to optimize β-lactam use for patients with pneumonia and surgical prophylaxis. 

This single center, retrospective, cohort study analyzed the impact of the implementation of the cross-reactivity chart in conjunction with enhanced assessment.  Impact was determined by assessing antibiotic use and associated outcomes in patients with β-lactam allergies in quasi-experimental pre-post study designs.  Propensity-weighted scoring analyses compared categorical and continuous outcomes.  Interrupted time-series analysis further analyzed key outcomes.

A total of 2,208 adult surgical patients were included, 1,119 and 1,089 in the historical and intervention cohorts, respectively.1  There was a significant difference in the number of patients who received an alternative antibiotic between the historical and intervention cohorts (84.9% vs. 15.1%, p < 0.001).  The use of preferred therapy significantly improved in all patient allergy types and across all procedure types.  There was no change in the rate of allergic reactions between cohorts (0.5% vs. 0.3%; p = 0.323).  There were significant increases in the patients who received recommended antibiotic timing (93.7% vs. 95.9%; p = 0.003), antimicrobial selection (92.6% vs. 96.2%, p < 0.001), and duration of antibiotic prophylaxis between cohorts (98.3% vs. 99.2%; p = 0.05). 

A total of 341 and 623 patient encounters were included in the historical and intervention pneumonia cohorts, respectively.  There was a significantly greater use of β-lactams in the intervention cohort (70.4% vs 89.3%; p < 0.001) and decreased use of alternative therapy (58.1% vs. 36%; p < 0.001).  There was no difference in overall allergic reactions between cohorts (2.4% vs. 1.6%; p = 0.738) or in reactions caused by β-lactams (1.3% vs. 0.9%; p = 0.703).  Healthcare facility-onset CDI decreased between cohorts (1.2% vs. 0.2%; p = 0.032).

In summary, implementation substantially improved the prescribing of preferred β-lactam antibiotics without increasing allergic reactions.  Active strategies incorporating side-chain-based allergy assessment, antimicrobial stewardship, and pharmacist review may be an easily implemented, inexpensive, effective, and deployable ‘best practice’ for pharmacies to incorporate into their suites of existing allergy stewardship strategies with the potential for wide-scale influential change.

St. Joseph Mercy Health System