Diagnostic testing in suspected fluoroquinolone hypersensitivity.

BACKGROUND: Because of their broad antibacterial activity in the gram-negative and gram-positive spectrum, high oral bioavailability, and good tissue penetration, fluoroquinolone antibiotics are widely used. Besides direct drug-related side-effects, fluoroquinolones may cause hypersensitivity reactions.
OBJECTIVE: The aim of this retrospective analysis was to present the results of diagnostic testing in cases of clinically suspected fluoroquinolone-induced immediate or delayed hypersensitivity.
METHODS: We studied 101 patients with a history of immediate or delayed hypersensitivity symptoms in temporal relation to treatment with a fluoroquinolone antibiotic using standardized skin testing, followed by oral challenges. Patients with anaphylaxis symptoms were further evaluated with in vitro tests.
RESULTS: Fluoroquinolone hypersensitivity was excluded in 71 patients by tolerated oral challenge tests. During positive challenge tests, six patients (three out of these had positive and three had negative skin prick tests) developed anaphylaxis symptoms but the presumed IgE-mediated mechanism could not be confirmed by in vitro tests. Patch testing was constantly negative; however, in two patients a rash was induced by the challenge tests.
CONCLUSION: History alone leads clearly to a considerable over-estimation of fluoroquinolone hypersensitivity. Moreover, skin or in vitro tests do not seem to be very useful in identifying hypersensitive patients. Challenge tests appear to be necessary for definitely confirming or ruling out fluoroquinolone hypersensitivity.