Allergologic work-up in diagnosing amoxicillin hypersensivity in children

Key words: Amoxicillin, Hypersensitivity, Children

Introduction - Adverse reactions to antibiotics, in particular to Amoxicillin, are frequently reported by parents but the allergologic work-up confirms a true state of drug hypersensitivity only in a small percentage of cases.
Objective - The aim of this study was to evaluate the utility of the skin tests methods and of the specific serum IgE assays in the diagnosis of mild-moderate Amoxicillin hypersensitivity reactions in children.
Materials and methods - 52 children (mean age 7.48 years) with history of mild-moderate cutaneous adverse reactions following the ingestion of Amoxicillin syrup were examined; the clinical manifestations of hypersensitivity were classified as immediate and non immediate according to the timing of the reaction (within 1 hour and after 1 hour from the last drug intake, respectively). Patients underwent skin tests (Skin Prick Test and Intradermal Test), determination of total and specific serum IgE with an immunoassay method (UNICAP) and with the epoxy-activated sepharose 6 B radioimmunoassay. All children underwent the Oral Provocation Test (OPT) with Amoxicillin.
Results - 13/52 (25%) and 39/52 (75%) children had history of immediate and non immediate reactions to Amoxicillin, respectively. The OPT resulted positive in 2 out of 13 (15.4%) and in 5 out of 39 (12.8%) of patients with history of immediate and non immediate reactions, respectively. In 3 children with history of immediate reactions, Amoxicillin specific serum IgE were detected by skin tests or in vitro tests and among them only one child had a positive OPT. None of those 32 subjects with history of non immediate reactions, who took the skin tests, had a positive response to immediate reading of the intradermal test, whereas one child had a positive delayed intradermal response. 6 out of 39 children with history of non immediate reactions had specific serum IgE; it was shown by the epoxy-activated method and among them 3 children had also a positive OPT. None of the 39 subjects had positive results with the UNICAP. All OPT-positive subjects showed mild skin reactions.
Conclusions - The present study highlights the weak utility of the in vivo and in vitro tests in the diagnosis of non immediate Amoxicillin hypersensitivity reactions and on the other hand, it emphasizes the importance and the relative safety of the OPT.