A Prospective Observational Study of the Effect of Penicillin Skin Testing on Antibiotic Use in the Intensive Care Unit

BACKGROUND: Patients with penicillin allergy admitted to the intensive care unit (ICU) frequently receive non-beta-lactam antimicrobials for the treatment of infection. The use of these antimicrobials, more commonly vancomycin and fluoroquinolones, is associated with the emergence of multidrug-resistant infections. The penicillin skin test (PST) can help detect patients at risk of developing an immediate allergic reaction to penicillin and those patients with a negative PST may be able to use a penicillin antibiotic safely. METHODS: We determined the incidence of true penicillin allergy, the percentage of patients changed to a beta-lactam antimicrobial when the test was negative, the safety of the test, and the safety of administration of beta-lactam antimicrobials in patients with a negative test. Skin testing was performed using standard methodology. RESULTS: One hundred patients admitted to 4 ICUs were prospectively studied; 58 of them were male. The mean age was 63 years. Ninety-six patients had the PST: one was positive (1.04%), 10 (10.4%) were nondiagnostic, and 85 (88.5%) were negative. Of the 38 patients who received antimicrobials for therapeutic reasons, 31(81.5%) had the antibiotic changed to a beta-lactam antimicrobial after a negative reading versus 7 patients of the 57 (12%) who had received a prophylactic antimicrobial (P < .001). No adverse effects were reported after the PST or after antimicrobial administration. CONCLUSIONS: The PST is a safe, reliable, and effective strategy to reduce the use of non-beta-lactam antimicrobials in patients who are labeled as penicillin allergic and admitted to the ICU.