Penicillin skin testing in patients with a history of β-lactam allergy

Background: Vancomycin and fluoroquinolones are commonly used in patients with a history of penicillin allergy. Objective: To determine the safety and utility of penicillin skin testing (PST). Methods: Retrospective study of patients with a history of penicillin allergy between April 1, 1999, and September 30, 2004. Penicillin skin testing was performed by means of standard methods using benzylpenicilloyl-polysine, penicillin G, and histamine and saline controls. Results: Of 596 patients studied, 25.3% were outpatients, 50.3% were inpatients, and 24.3% were intensive care unit patients. The most common antibiotics used during the time of PST were vancomycin and fluoroquinolones. Results of PST were negative in 88.4% of patients, positive in 8.2%, and indeterminate in 3.4%. One patient (0.17%) developed urticaria immediately after PST. Fifty-five percent of patients with negative PST results were changed to a beta-lactam drug, more frequently in the intensive care unit vs the outpatient setting (70.3% vs 8.6%; P < .001) and in adults vs patients younger than 18 years (58.6% vs 8.1%; P < .001). A beta-lactam antibiotic was used in 290 patients with negative PST results. Of the patients given beta-lactam antibiotics, 5 (1.7%) had adverse reactions: 2 had hives after 16 and 20 days of therapy, I had a nonspecific rash after 17 days of therapy, I had flushing and urticaria 3 hours after a test dose of piperacillin-tazobactam, and I had a pruritic rash after 12 hours of therapy. Conclusions: Patients with a history of penicillin allergy can safely use beta-lactam drugs if negative PST results.