Nonirritant intradermal skin test concentrations of ciprofloxacin, clarithromycin, and rifampicin

Background: Intradermal skin testing of the clinically important antibiotics ciprofloxacin, clarithromycin, and rifampicin in the case of suspected allergies to antibiotics is poorly standardized. For clinical practice, standardized procedures and protocols are desired. Methods: Fifteen healthy volunteers were tested with different concentrations of the antibiotics as well as with appropriate controls. Test readings included wheal area measured by digital image analysis and blood flow increase measured by laser Doppler flowmetry (LDF). To reduce interpersonal variability, test results were normalized with the individual controls using a novel protocol. Results: Nonirritating concentrations of the three antibiotics (ciprofloxacin similar to 0.0067 mg/ml, clarithromycin similar to 0.05 mg/ml, rifampicin similar to 0.002 mg/ml) could be defined for healthy volunteers. Laser Doppler flowmetry generates comparable results to wheal area measurement. Normalization of the test results is necessary and can be applied in a practical algorithm. Conclusions: Standardized skin testing to detect sensitization to broadly used nonbetalactam antibiotics was presented and should be applied in truly sensitized patients. This approach should help to minimize the inter-and intraindividual differences in reactivity.