Full-Course Drug Challenge Test in the Diagnosis of Delayed Allergic Reactions to Penicillin

Background: Drug challenge test (DCT) has long been the most sensitive test in the allergological work-up when investigating for penicillin allergy. Objective: To improve sensitivity of the diagnostic work-up in diagnosing penicillin allergics with histories of allergic reactions on day 2 or later in the course of penicillin treatment. Methods: A full-course DCT was added to the current protocol if specific IgE, skin tests and DCT were all negative in patients who had a nonimmediate reaction to penicillin treatment. Sixteen patients with a history of an immediate reaction to penicillin treatment underwent testing with negative outcomes. Results: Fifty percent of patients undergoing full-course DCT experienced a cutaneous adverse drug reaction. None of the controls reacted (p = 0.001). The mean time of reaction was 6 days. Penicillin V accounted for most reactions. Urticaria was the most frequent clinical reaction observed. Conclusions: Full-course DCT offers an improvement of sensitivity and predictive values of the diagnostic work-up of allergic reactions to penicillin occurring on day 2 of penicillin treatment or later. Copyright (C) 2011 S. Karger AG, Basel