Novel testing to aid antibiotic prescribing in severe antibiotic allergy (SCAR)

Published online: October 31, 2017

Severe cutaneous adverse reactions (SCAR), such as Stevens-Johnson syndrome, frequently occur secondary to antibiotics, and in these patients, mortality can be upwards of 25%. Due to the severity of such reactions, prescribing antibiotics post SCAR is problematic for doctors, especially in the era of antibiotic-resistant infections. Currently there remains no widely available test to assign causality in SCAR and aid appropriate antibiotic prescribing post event.

The study by Trubiano and colleagues recently published in The Journal of Allergy and Clinical Immunology: In Practice explores the use of traditional skin testing (in vivo) with novel blood tests (ex vivo) to aid antibiotic prescribing in a group of antibiotic-associated SCAR patients.

Patients underwent in vivo skin testing to the implicated antibiotics in addition to blood being utilized for ex vivo T-cell studies. The ex vivo studies examined T-cell responses to the implicated antibiotics via an Enzyme Linked ImmunoSpot (ELISpot) assay, measuring the release of a key immune mediator (IFN-γ) that is produced during SCAR. Patients were followed post testing to examine the impacts of testing on safe antibiotic prescribing.

Trubiano et al. demonstrated that in 79% of patients with a history of antibiotic-associated SCAR, the causative antibiotic could be assigned utilizing combined in vivo (skin testing) and ex vivo (IFN-γ release ELISpot) tests. Fifty-two percent of patients were positive to one or more antibiotics on in vivo testing, with no adverse events reported. Fifty-three per cent of patients were positive on the IFN-γ release ELISpot assay. There was an increased use of narrow-spectrum antibiotics and those with a similar structure to the implicated antibiotics in patients with a positive test (ex vivo or in vivo).

This study, in one of the largest cohorts of antibiotic-associated SCAR, demonstrated the potential utility of combining skin (in vivo) and blood (ex vivo) testing. In the future, improving the safe and appropriate use of antibiotics in patients with a history of severe antibiotic allergy may be improved by the combination of traditional skin testing with novel diagnostics.

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.

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