Practical management of positive norovirus results from FilmArray® GI panel

BACKGROUND: On February the 7th 2024, BioFire® alerted users to a risk of false-positive norovirus results with the BioFire® FilmArray® Gastrointestinal Panel (BF-GIP) and recommended confirmatory testing. OBJECTIVES: To assess the reliability of BF-GIP norovirus-positive results in children and develop a decision algorithm for managing potential false positives. STUDY DESIGN: Between January and June 2025, all BF-GIP norovirus-positive samples were re-tested the same day using the GeneXpert® Norovirus assay (Cepheid®). BF-GIP cycle thresholds (Ct) values and melting curves were analyzed. RESULTS: Of the 1007 BF-GIP performed, 131 were norovirus-positive and 127 were retested by the GeneXpert® Norovirus assay. Overall, 31.5 % (40/127) were discordant. Atypical melting curves (22/40, 55 %), high Ct values (> 25) or "N/A" results were strongly associated with discordance, while Ct ≤ 20 were highly predictive of concordance. Based on these metrics, 58 % of BF-GIP norovirus-positive results could be confidently confirmed or rejected without additional testing. CONCLUSION: False norovirus-positive results by the BF-GIP are common. An algorithm integrating BF-GIP Ct values and melting curve analysis can reduce unnecessary retesting, streamline laboratory workflow and support accurate diagnosis in pediatric settings.