Standardization of Basophil Activation Testing (BAT) remains a major challenge for its integration in clinical studies. Variability between reagent lots and limited stability data may bias longitudinal interpretation. Ready-to-use dry BAT tubes represent an attractive approach, but their long-term reproducibility has not been evaluated yet.

This study aimed to evaluate inter-lot variability and long-term stability of peanut dried BAT tubes, performed across multiple donors and multiple storage times.

Whole blood samples from 8 donors allergic to peanut were activated with serial dilutions of peanut extract prepared in dry BAT tubes. For each donor, dose–response curves were generated in parallel with 8 identical lots, at 8 different timepoints. Basophil were identified as SSlowCD45+ CD3-CRTH2+ and their activation was quantified based on CD63 and CD203c upregulation after stimulation.

Across all donors, lots, and timepoints, dose-response curves were highly consistent. Despite a difference of 16 months over the different manufactured tubes, inter-lot variability was minimal, with CVs consistently low for maximal activation values. Repeated testing at distant timepoints on different donors confirmed the long-term stability of the dried-tube format and its ability to support reproducible activation curves even in highly responsive donors. No drift was observed over the seven-year range of tube production and storage.

Ready-to-use dried BAT tubes provide excellent reproducibility across manufacturing lots and maintain low lot-to-lot variability over several years. These findings support their suitability for longitudinal clinical studies, minimizing analytical variability and reducing the risk of misinterpreting lot-related fluctuations as true biological changes. This format may facilitate broader adoption of BAT as a reliable functional biomarker in food allergy research.