Immunocap® ISAC and microtest for multiplex allergen testing in people with difficult to manage allergic disease: A systematic review and cost analysis

__Background__ Allergy is a form of immune-mediated exaggerated sensitivity (hypersensitivity) to a substance that is either inhaled, swallowed, injected or comes into contact with the skin. Foreign substances that provoke allergies are called allergens. It has been claimed that multiplex allergen testing may help in diagnosing the cause of symptoms in patients with an unclear cause of allergy or who are allergic to more than one substance. __Objectives__ To evaluate multiplex allergen testing [devices that can measure the presence of multiple immunoglobulin E (IgE) antibodies in a patient’s blood at the same time], by assessing (1) clinical effectiveness (allergy symptoms, incidence of acute exacerbations, mortality, adverse events of testing and treatment, health-care presentations or admissions, health-related quality of life); (2) effects on treatment (diet, immunotherapy medications, other potential testing); (3) any additional diagnostic information provided by multiplex allergen testing; and (4) cost-effectiveness (cost of different assessment strategies). __Methods__ Fifteen databases were searched from 2005 to April 2015, including MEDLINE (via OvidSp), MEDLINE In-Process Citations, MEDLINE Daily Update, PubMed (National Library of Medicine), EMBASE, Cochrane Database of Systematic Reviews (CDSR), Cochrane Central Register of Controlled Trials (CENTRAL), Database of Abstracts of Reviews of Effects (DARE), Health Technology Assessment (HTA) database, Science Citation Index (SCI), Conference Proceedings Citation Index-Science (CPCI-S), BIOSIS Previews, Latin American and Caribbean Health Sciences Literature (LILACS), National Institute for Health Research (NIHR) HTA programme, and the US Food and Drug Administration (FDA); supplementary searches of conference proceedings and trials registries were performed. Review methods followed published guidance from the Cochrane Collaboration and the Centre for Reviews and Dissemination, University of York, UK. The methodological quality of included studies was assessed using appropriate published tools or a review-specific tool designed by the project team. Studies were summarised in a narrative synthesis. Owing to a lack of data on the clinical effectiveness of multiplex allergen testing, no long-term cost-effectiveness model was developed. A conceptual model structure was developed and cost analyses were performed to examine the short-term costs of various possible diagnostic pathways. __Results__ Fifteen studies were included in the review. The very limited available data indicated that the addition of multiplex allergen testing [ImmunoCAP® Immuno Solid-phase Allergen Chip (ISAC), Thermo Fisher Scientific/Phadi