D2.19 - Can Drug Provocation Be Avoided in Low-Risk Quinolone Reactions?

 Quinolones are frequently reported as suspected causes of drug hypersensitivity, although many reactions are clinically nonspecific. Some manifestations, such as erythema, phlebitis, pruritus or other nonspecific symptoms, may be related to non–IgE-mediated mechanisms, including direct mast cell activation through receptors such as MRGPRX2, rather than true allergic hypersensitivity. This study aimed to assess the diagnostic yield of skin tests and drug provocation tests (DPT) in patients with suspected quinolone hypersensitivity, focusing on reactions with low clinical probability.

 We conducted a retrospective observational study in a tertiary hospital. Using the Orion Clinic electronic medical record system, patients evaluated for suspected allergy to ciprofloxacin and/or levofloxacin between August 2024 and August 2025 were identified. Of a total of 88 screened patients, 43 fulfilled inclusion criteria and were included for analysis. Reactions were classified according to clinical presentation, and results of skin tests and DPTs were analyzed.

 Among the 43 included patients, reported reactions were erythema (n=10, 23.3%), phlebitis (n=9, 20.9%), urticaria (n=8, 18.6%), pruritus (n=4, 9.3%), gastrointestinal symptoms (n=2, 4.7%), exanthema (n=3, 7.0%), unknown reactions (n=2, 4.7%), angioedema (n=1, 2.3%), anaphylaxis (n=1, 2.3%), and other nonspecific symptoms (n=3, 7.0%).Reactions considered of low probability for true hypersensitivity—including erythema, phlebitis, pruritus, gastrointestinal symptoms, unknown reactions and other nonspecific symptoms—accounted for 69.8% of cases. In this group, skin tests were negative in all but one patient, who presented pruritus and showed a positive skin test to levofloxacin; subsequent drug provocation with ciprofloxacin was negative. All DPTs performed in the low-probability group were negative. Positive diagnostic results were observed exclusively in patients with higher-risk presentations, such as urticaria, angioedema, and anaphylaxis.

Nearly 70% of suspected quinolone reactions were of low clinical probability and showed a very low yield of diagnostic testing. These findings support a more selective diagnostic approach, in which negative skin tests in carefully evaluated low-risk patients may allow safe use of quinolones without systematic drug provocation testing.