Negative Test, Persistent Avoidance: Real-World Outcomes of Quinolone De-Labeling.

Background/Objectives: Quinolones are among the most frequently implicated antibiotics in immediate hypersensitivity reactions, yet diagnostic evaluation remains challenging and the real-world behaviour of patients after de-labeling has received little attention. We examined the diagnostic work-up, outcomes, and post-de-labeling drug-use behaviour of patients with suspected quinolone hypersensitivity. Methods: This single-centre ambispective study included 29 patients evaluated between January 2020 and April 2024. Clinical, demographic, skin test, and drug provocation test (DPT) data were extracted retrospectively. Patients in whom allergy had been excluded or a safe alternative identified were contacted by structured telephone interview between May and June 2025. Results: Anaphylaxis was the most common index reaction (42.9%), and ciprofloxacin was the most frequently implicated agent (57.1% of drug instances). Skin tests were positive in 84.2% of cases, but the positive predictive value in the DPT-tested subset was only 20.0%. Of the 12 reached patients, 11 had quinolone allergy excluded; among these, only 4 (36.4%) had reused the de-labeled quinolone, while 7 (63.6%) had avoided it, including 4 who declined it when clinically indicated. Conclusions: Quinolone skin tests show limited specificity, and successful de-labeling does not guarantee real-world drug use. Patient anxiety and counselling are central to effective management.