Signal without noise: Practical antibody titration for platelet flow cytometry

Antibody titration is essential for optimizing platelet flow cytometry, a technique widely used to evaluate platelet phenotype, activation status, and function. This manuscript outlines practical approaches for platelet antibody titration in whole blood, with tailored strategies for constitutive and inducible markers. It emphasizes the use of appropriate controls, consideration of marker coexpression, and selection of subsaturating antibody concentrations to maximize signal resolution while minimizing background and artifactual activation. Quantitative metrics such as the stain index and separation index are introduced as tools for evaluating staining performance. The discussion also addresses key technical variables, including combinatorial titration, spillover spreading, lot variability, and antibody-induced activation. Titration under final assay conditions is recommended to ensure reproducibility and biological relevance. These strategies provide a foundation for developing robust, high-resolution platelet assays that support both research and clinical applications, particularly as flow cytometry evolves toward greater automation and standardization.