Background: ß-lactam (BL) antibiotics represent the main cause of allergic reactions to drugs, inducing both immediate and non-immediate reactions. The diagnosis is well established, usually based upon skin tests and drug provocation tests, but cumbersome.

Objectives: To design predictive models for the diagnosis of BL allergy, based on the clinical history of patients with suspicions of allergic reactions to BL.

Methods: The study included a retrospective phase in which records of patients consulting and explored for a suspicion of BL allergy (in the Allergy Unit of the University Hospital of Montpellier between September 1996 and September 2012) where used to construct predictive models; a prospective phase, in which we performed an external validation of the chosen models, in patients with suspicion of BL allergy recruited from 3 allergy centres (Montpellier, Nîmes, Narbonne), between March and November 2013. Data related to clinical history and allergy work-up results were retrieved and analysed. Logistic regression and decision tree method were used to design two models to predict the diagnosis of allergy to BL.

Inclusion Criteria:

• Patients seen in consultation in allergology department for suspicion of allergy to beta lactamines

Exclusion Criteria:

• patient refusal to take part in the study
• pregnancy
• breast feeding women
• contraindication to provocation test

Patients seen in consultation in allergology department for suspicion of allergy to beta lactamines