Health care use and serious infection prevalence associated with penicillin "allergy" in hospitalized patients: A cohort study.

BACKGROUND Penicillin is the most common drug "allergy" noted at hospital admission, although it is often inaccurate. OBJECTIVE We sought to determine total hospital days, antibiotic exposures, and the prevalence rates of Clostridium difficile, methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant Enterococcus (VRE) in patients with and without penicillin "allergy" at hospital admission. METHODS We performed a retrospective, matched cohort study of subjects admitted to Kaiser Foundation hospitals in Southern California during 2010 through 2012. RESULTS It was possible to match 51,582 (99.6% of all possible cases) unique hospitalized subjects with penicillin "allergy" to 2 unique discharge diagnosis category-matched, sex-matched, age-matched, and date of admission-matched control subjects each. Cases with penicillin "allergy" averaged 0.59 (9.9%; 95% CI, 0.47-0.71) more total hospital days during 20.1 ± 10.5 months of follow-up compared with control subjects. Cases were treated with significantly more fluoroquinolones, clindamycin, and vancomycin (P < .0001) for each antibiotic compared with control subjects. Cases had 23.4% (95% CI, 15.6% to 31.7%) more C difficile, 14.1% (95% CI, 7.1% to 21.6%) more MRSA, and 30.1% (95% CI, 12.5% to 50.4%) more VRE infections than expected compared with control subjects. CONCLUSIONS A penicillin "allergy" history, although often inaccurate, is not a benign finding at hospital admission. Subjects with a penicillin "allergy" history spend significantly more time in the hospital. Subjects with a penicillin "allergy" history are exposed to significantly more antibiotics previously associated with C difficile and VRE. Drug "allergies" in general, but most those notably to penicillin, are associated with increased hospital use and increased C difficile, MRSA, and VRE prevalence.