The impact of penicillin skin testing on clinical practice and antimicrobial stewardship.

Background: Penicillin skin testing (PST) is a simple and reliable way of diagnosing penicillin allergy. After being off the market for 4 years, penicilloyl-polylysine was reintroduced in 2009 as PRE-PEN. We describe the negative predictive value (NPV) of PST and the impact on antibiotic selection in a sample of hospitalized patients with a reported history of penicillin allergy.

Methods: We introduced a quality improvement process at our 861-bed tertiary care hospital that used PST to guide antibiotic usage in patients with a history consistent with an immunoglobulin E (IgE)-mediated reaction to penicillin. Subjects with a negative PST were then transitioned to a β-lactam agent for the remainder of their therapy. NPV of skin testing was established at 24-hour follow-up. We are reporting the result of 146 patients tested between March 2012 and July 2012.

Results: A total of 146 patients with a history of penicillin allergy and negative PST were treated with β-lactam antibiotics. Of these, only 1 subject experienced an allergic reaction to the PST. The remaining 145 patients tolerated a full course of β-lactam therapy without an allergic response, giving the PST a 100% NPV. We estimated that PST-guided antibiotic alteration for these patients resulted in an estimated annual savings of $82,000.

Conclusion: Patients with a history of penicillin allergy who have a negative PST result are at a low risk of developing an immediate-type hypersensitivity reaction to β-lactam antibiotics. The increased use of PST may help improve antibiotic stewardship in the hospital setting.