Fundamentals of laboratory diagnostics in allergology

Summary The diversity of allergic disorders and their associated underlying mechanisms render allergy diagnosis particularly challenging. There is a palette of available in vivo and in vitro tests, while result interpretation must always be made in conjunction with clinical history. The focus of the present article is on laboratory diagnostics, where several diagnostic tests have been developed targeting different parts of the allergic cascade. The results of these tests may indicate the presence of clinical allergy but also provide information on disease severity, treatment options, and therapy responsiveness. First-line testing involves allergen specific IgE (sIgE) antibody measurements, and several considerations are required when choosing the exact test. Among others, the allergens to be tested, the use of allergen extracts versus molecular components, cross-reactivity aspects, cost, and geographical sensitization patterns need to be considered. There are technical distinctions between main commercially available automated platforms, which is often reflected by differences in their test results. Diagnostically challenging cases can be supplemented by tests assessing the key effector cells, i.e., basophils, mast cells, and eosinophils, as well as by tests targeting several of the released mediators, including tryptase, lipids, and histamine. Overall, non-IgE-based laboratory tests need additional standardization and research to support their clinical utility.