Penicillin skin testing in hospitalized patients with β-lactam allergies: Effect on antibiotic selection and cost.

BACKGROUND: A history of a penicillin allergy generally leads to the use of broad-spectrum antibiotics that may increase complications and cost.

OBJECTIVE: To determine the cost-effectiveness of performing penicillin skin testing (PST).

METHODS: A retrospective analysis was conducted on adult inpatients with a β-lactam allergy who underwent PST and oral challenge performed by an allergist. The primary outcome was overall antibiotic cost savings for patients switched to a β-lactam antibiotic (BLA). Secondary outcomes included subsequent admissions that required antibiotics and total number of days a BLA was prescribed.

RESULTS: Fifty patients had PST performed (mean age, 62 years). The most common β-lactam allergy reported was penicillin (92%). Cutaneous reactions were reported in 54% of patients, and 56% had a reaction more than 20 years ago. Fifty percent of patients had aztreonam prescribed before PST. The results of PST were negative in all patients, and 1 patient had anaphylactic symptoms during the oral amoxicillin challenge (98% skin test or oral challenge negative). Thirty-seven patients (75.5%) were changed to a BLA. Overall cost savings were $11,005 ($297 per patient switched to a BLA). There were 31 subsequent admissions that required antibiotics for patients who tested negative on skin test and oral challenge. A BLA was prescribed in 22 of 31 readmissions, totaling 147 days of BLA therapy.

CONCLUSION: After the implementation of a PST protocol, we observed a decrease in non-BLA use in patients with previously documented β-lactam allergy. PST is a safe and cost-effective procedure to serve as a negative predictor test for penicillin hypersensitivity mediated by IgE.