Objective: To evaluate antibiotic selection and the cost effect of reported β-lactam allergies. Design: Retrospective medical records review comparing antimicrobial selection and costs in patients with a reported β-lactam allergy with a group in which no such allergy had been documented. Setting: University-based family medicine clinic. Patients: Patients who were prescribed at least 1 antibiotic for an upper respiratory tract infection, otitis media, sinusitis, and/or a urinary tract infection were eligible. One thousand two hundred one patients were identified via ICD-9-CM (International Classification of Diseases, Ninth Revision, Clinical Modification) codes. Four hundred sixty-five patients were initially identified and an additional 195 family members were eligible for inclusion. Main Outcome Measures: Comparison of antimicrobial selection and costs (by average wholesale price) between patients with and without a reported β-lactam allergy. Results: Of the 660 patients eligible for inclusion, 99 (15%) had a documented β-lactam allergy. Of the patients with a documented allergy, only 33% had a description of their purported reaction. The mean antibiotic cost for patients with a β-lactam allergy was significantly higher compared with those without a β-lactam allergy ($26.81 vs $16.28, respectively; P = .004). Patients with a β-lactam allergy were more likely to have received a cephalosporin, macrolide, or a miscellaneous agent (eg, quinolone, tetracycline, or nitrofurantoin) (P = .001). Conclusions: Patients with a β-lactam allergy had higher antibiotic costs and were more likely to receive a broader-spectrum antibiotic. Most patients with a reported allergy did not have a description of their reaction. Skin testing may be of use in detecting true β-lactam allergies; however, further study is needed to determine its cost-effectiveness.
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