The overall aim of this project was to summarise the evidence available to inform estimates of the clinical effectiveness and cost-effectiveness of adding multiplex allergen testing to the investigation of people with difficult to manage allergic disease, in secondary or tertiary care settings. Multiplex allergen testing may replace some single immunoglobulin E (IgE) testing, but, where the multiplex testing panel does not include all of the suspected allergens, additional single specific IgE (sIgE) tests may be needed.

We defined the following research objectives to address this aim:

• To assess the effects on clinical outcomes [e.g. allergy symptoms, incidence of acute exacerbations, mortality, adverse events (AEs) of testing and treatment, health-care presentations or admissions, health-related quality of life (HRQoL)] of adding multiplex allergen testing to the investigation of people with difficult to manage allergic disease.
• To assess the effects on treatment (e.g. restriction diets, immunotherapy, use of other medications such as corticosteroids, number of allergen challenge tests required) of adding multiplex allergen testing to the investigation of people with difficult to manage allergic disease.
• To assess the accuracy of multiplex allergen testing in predicting clinical reactivity (response to allergen challenge testing or response to immunotherapy) and to investigate whether or not multiplex allergen testing can provide diagnostic information additional to that provided by current standard care in the UK (clinical history, skin prick tests) and single IgE testing or a combination of these approaches).
• To assess the cost-effectiveness of adding multiplex allergen testing to the investigation of people with difficult to manage allergic disease in secondary or tertiary care settings.
• This report contains reference to confidential information provided as part of the National Institute for Health and Care Excellence (NICE) appraisal process. This information has been removed from the report and the results, discussions and conclusions of the report do not include the confidential information. These sections are clearly marked in the report.