Production and Applicability Evaluation of External Quality Assessment Materials for Proficiency Testing of Rapid Influenza Antigen Test

Background: The increased use of rapid antigen tests (RATs) for influenza viruses, particularly in primary care clinics, has made external quality assessment (EQA) an essential component of quality management.While EQA programs have been successfully implemented for serological and molecular tests, suitable materials and protocols for antigen-based assays are still under development.This study aimed to produce EQA materials and evaluate their applicability for RATs available in the domestic market.Methods: Saline-diluted influenza A/B virus cultures were evaluated using three widely used RAT kits for both visual and instrument-based interpretation.The stability of the EQA materials was assessed using instrument-read RATs under icebox storage conditions.A pilot-scale EQA was conducted after reviewing the RATs, using samples of influenza A (H1N1/ H3N2), influenza B (Yamagata lineage), and a negative control.Results: Influenza A H1N1, H3N2, and influenza B culture samples with concentrations above 10 5 pfu/mL consistently tested positive across all three kits.The antigen stability of influenza B samples was lower than that of influenza A samples.In the EQA involving 10 domestic laboratories, all participants provided the intended responses.Notably, at one institution, influenza A H1N1 and H3N2 yielded negative results with the kit's buffer, whereas applying the sample directly without the buffer produced positive results.Conclusions: This study demonstrates the feasibility of using viral culture fluids as EQA materials for influenza RATs.Nevertheless, challenges remain, such as the large number of testing institutions, difficulty in mass-producing viral culture fluids, and variability among kit buffer solutions, which warrant further consideration.