Flow Cytometry‐Assisted Analyses of Individual Human Basophils, Mast Cells and T Cells in the Diagnosis of Immediate Drug Hypersensitivity: A Review

Immediate drug hypersensitivity reactions (IDHRs) pose significant diagnostic challenges, often requiring potentially hazardous drug challenge testing (DCT). Flow cytometry-based cellular tests including the basophil activation test (BAT), the mast cell activation test (MAT) and the T cell activation test (TAT) offer promising alternatives to reduce DCT reliance. While these tests are still in development, they demonstrate potential to compete with skin tests by providing superior diagnostic performance and improved patient safety by reducing the need for DCT. Furthermore, it is encouraging that these flow cytometry-based tests are also suitable for challenging populations, such as children. Despite requiring specialised infrastructure, these tests have the potential to be cost-effective when performed in reference centres and may offer unique mechanistic insights into immediate drug hypersensitivity reactions. However, further research is needed to validate their reliability, address pharmaceutical-specific testing considerations, and potentially integrate them into clinical guidelines.