Impact of an extended challenge on the effectiveness of β-lactam hypersensitivity investigation.

Background: Drug provocation tests (DPTs) are the gold standard in the diagnosis of β-lactam hypersensitivity. However, no consensus exists on the need for extended provocation tests, even though the effectiveness of the short DPT is relatively low and there has been an increase in the relative incidence of nonimmediate hypersensitivity reactions.

Objective: To evaluate the effectiveness of a 7-day (extended) DPT compared with a 1-day-only (short) DPT in the management of hypersensitivity reactions to β-lactam antibiotics.

Methods: Patients referred to the allergy clinic of the Sheba Medical Center for suspected β-lactam hypersensitivity from January 2008 to December 2012 underwent in vivo skin tests and an immediate short DPT with the culprit drug. Unless an immediate reaction was clearly documented, patients were offered a 7-day, extended DPT. Long-term effectiveness, calculated as the subsequent use of the tested antibiotic, and satisfaction levels were assessed with a telephone questionnaire.

Results: Of 49 negative DPT results, 26 (53%) were long and 23 (47%) were short. A total of 78% of the patients who underwent the long DPT reported that they used the drug compared with 61% of those who underwent only the short DPT (P = .049). Most patients were very satisfied with the drug allergy evaluation process.

Conclusions: An extended DPT protocol increased the effectiveness of the allergy workup in our center without compromising patient satisfaction and safety, and it should be recommended to patients with a history of nonimmediate reaction to β-lactam.