Oral challenge necessary for diagnosis of fluoroquinolone allergy, skin/in vitro tests not enough

Fluoroquinolone antibiotics are widely used for several reasons:

- broad antibacterial activity in the gram-negative and gram-positive spectrum
- high oral bioavailability
- good tissue penetration

Fluoroquinolones may cause hypersensitivity reactions.

101 patients with a history of immediate or delayed hypersensitivity in temporal relation to fluoroquinolones were assesed with skin testing, followed by oral challenges.

Patients with anaphylaxis symptoms were further evaluated with in vitro tests.

Fluoroquinolone hypersensitivity was excluded in 71 patients by tolerated oral challenge tests.

During positive challenge tests, 6 patients (3 with positive and 3 with negative skin prick tests) developed anaphylaxis. However, IgE-mediated mechanism could not be confirmed by in vitro tests.

Patch testing was negative. History alone leads clearly to a considerable over-estimation of fluoroquinolone hypersensitivity.

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.

Mnemonic for diagnosis of drug allergy

HASTA la vista (Spanish, See you later)

History
Assemble a list of drugs and rank them
Stop all drug candidates
Test
Administer - dose escalation or desensitization

References:
Diagnostic testing in suspected fluoroquinolone hypersensitivity. C. S. Seitz, E. B. Bröcker, A. Trautmann. Clinical & Experimental Allergy.

Basophil activation test for evaluation of IgE-mediated hypersensitivity reactions to quinolones http://goo.gl/LFEf
Mnemonics: Drug Allergy
Image source: Essential structure of all quinolone antibiotics: the blue drawn remainder of R is usually piperazine; if the connection contains fluorine (red), it is a fluoroquinolone. Wikipedia, public domain.