Skin testing and drug challenge outcomes in antibiotic-allergic patients with immediate-type hypersensitivity

Abstract Background The evaluation of antibiotic immediate-type hypersensitivity is intricate because of nonstandardized skin testing and challenge method variability. Objective To determine the safety outcomes and risk factors for antibiotic challenge reactions in patients reporting a history of antibiotic immediate-type hypersensitivity. Methods A 5-year retrospective review of patients evaluated for immediate-type antibiotic allergy was conducted. Data analyzed included patient demographics, index reaction details, and outcomes of skin testing and challenges, classified as single-step or multistep. Results Antibiotic hypersensitivity history was identified in 211 patients: 78% to penicillins, 10% to fluoroquinolones, 7.6% to cephalosporins, and 3.8% to carbapenems. In total, 179 patients completed the challenges (median age 67 years, range 50–76 years, 56% women), and compared with nonchallenged patients, they reported nonanaphylactic ( P < .001) and remote index ( P = .003) reactions. Sixteen patients (8.9%) experienced challenge reactions (5 of 28 for single-step challenge, 11 of 151 for multistep challenge), and 11 of these patients had negative skin testing results before the challenge. Challenge-reactive patients were significantly younger ( P = .007), more often women ( P = .036), and had additional reported antibiotic allergies ( P = .005). No correlation was detected between the reported index and observed challenge reaction severities (κ = −0.05, 95% confidence interval −0.34 to 0.24). Anaphylactic rates were similar during single-step and multistep challenges (3.6% vs 3.3%). Conclusion In the present population, younger women with multiple reported antibiotic allergies were at greatest risk for challenge reactions. Negative skin testing results did not exclude reactions, and index severity was not predictive of challenge outcome. The multistep and full-dose methods demonstrated a comparable reaction risk for anaphylaxis.