European Network on Drug Allergy (ENDA) has proposed an algorithm for diagnosing immediate beta-lactam (BL) allergy. We evaluated its performance in real life. During 1994-2014, 1779 patients with suspected immediate reactions to BL were evaluated following ENDA's short diagnostic algorithm. Five hundred and nine patients (28.6%) were diagnosed of BL hypersensitivity. Of them, 457 (25.7%) were at first evaluation [403 by skin tests (ST), 12 by positive IgE and 42 by controlled provocation tests (CPT)]. At second evaluation (SE), 52 additional patients (10.2% of allergic patients) were diagnosed, [50 (2.8%) by ST and 2 (0.1%) by CPT]. Time between reaction and study was significantly longer in patients diagnosed at SE (median 5 vs 42 months; IQR 34 vs 170; P < 0.0001). Anaphylaxis was significantly associated with a diagnosis at SE. European Network on Drug Allergy/EAACI protocol was appropriate and safe when evaluating BL immediate reactions. Re-evaluation should be performed, particularly when anaphylaxis and long interval to diagnosis are present.

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Background: Being labeled as allergic to penicillin (unverified ß-lactam allergy) can result in patients receiving broader-spectrum antibiotics than necessary that may be more toxic, less effective, and/or more expensive than alternative options. Objective: We aimed to evaluate the real costs of evaluating ß-lactam allergy. Methods: We performed a prospective real-life observational study designed to evaluate all adult patients who consulted for suspected ß-lactam allergy over a 1-year period. Direct and indirect costs were systematically recorded. Direct health costs were calculated based on the number of visits and all additional and diagnostic tests performed, direct nonhealth costs based on the number of visits and the distance from their homes to the Allergy Department, and indirect costs based on absenteeism. Results: A total of 296 patients with suspected allergy to ß-lactams were evaluated in our outpatient clinic from June 1, 2017 to May 31, 2018. Total direct health care costs were €28 176.70, with a mean (SD) cost of €95.19 (37.20). Direct nonhealth costs reached €6551.73, that is, €22.13 (40.44) per patient. Indirect health costs reached €20 769.20, with a mean of €70.17 (127.40). In summary, the total cost was €55 497.63, that is, a cost per patient of €187.49 (148.14). Conclusions: When all possible costs are taken into account, the evaluation of ß-lactam allergy is not expensive and can reduce future expense arising from unnecessary use of more expensive and less effective antibiotics.