Decoding allergy in vitro: Challenges and clinical use of humoral and cellular methods

In vitro assays are essential tools in diagnosing IgE-mediated allergic diseases and complement clinical history and skin testing across food, inhalant, venom, and drug allergies. This methodological review is intended for clinicians seeking a more detailed understanding of current laboratory-based allergy diagnostics. It summarizes current humoral and cellular diagnostic methods, including total IgE, singleplex and component-resolved specific IgE testing, multiplex IgE platforms, and functional cellular assays such as the basophil activation test and T-cell-based approaches. Humoral assays remain the quantitative foundation of molecular allergy diagnostics, while multiplex arrays broaden diagnostic scope and map sensitization profiles, although platform variability requires cautious interpretation. Cellular assays may add functional information in selected constellations but remain technically demanding, insufficiently standardized, and are best regarded as adjunctive tools in specialized or research settings, with evidence largely derived from selected cohorts. Additional areas - immunotherapy monitoring, mast cell disorders, contact allergy, and oncology - illustrate the broader methodological spectrum of in vitro methods. Persistent unmet needs include harmonization, validated reference standards, and robust interpretive frameworks. Disease-specific applications are discussed in companion articles in this issue.