AI Insight
The BioFire FilmArray Gastrointestinal Panel (BF-GIP), a widely used multiplex molecular diagnostic tool, was found to produce norovirus false-positive results at rates ranging from 31 to 74% across four hospital sites, with the highest rates observed at a specialized cancer care facility. Deep sequencing analysis identified the Noro-1 assay as the primary source of this problem, revealing 78 off-target amplification species, mostly commensal gut bacteria, compared to only two for the Noro-2 assay. False-positive samples showed significantly higher cycle threshold (Cp) values than true positives, consistent with low-level mispriming of gut microbiota rather than genuine norovirus detection.
Why it matters
These findings have direct clinical consequences, as false-positive norovirus diagnoses can lead to unnecessary isolation measures, delayed care, misattribution of symptoms in vulnerable patients such as cancer patients, and inappropriate resource use in healthcare settings. The study provides mechanistic evidence supporting the need to redesign the Noro-1 assay to restore diagnostic reliability.
⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Molecular syndromic panels such as the BioFire FilmArray Gastrointestinal Panel (BF-GIP) have been widely adopted for gastrointestinal illness diagnosis due to their fast turnaround times and broad pathogen coverage. Recently, the BF-GIP demonstrated increased rates of norovirus false-positive detections, prompting a Class II recall of more than two million tests in February 2024. We examined the prevalence of BF-GIP norovirus false positives across four hospitals from December 2024 to June 2025. Among 185 BF-GIP norovirus-positive results confirmed with the BD MAX Enteric Viral Panel, the false discovery rate ranged from 31 to 74% across sites, with the highest rate seen at a specialized cancer care hospital. Deep sequencing of BF-GIP pouches (n=42) confirmed the Noro-1 assay as the primary source of off-target amplification, identifying 78 off-target species, predominantly commensal stool bacteria, compared to only two species for the Noro-2 assay. Off-target species amplified by the Noro-1 assay were recovered from both false-positive and true-negative pouches, suggesting no single species accounted for the false-positive results. Partial primer complementarity at off-target loci and amplicon Tm values within the acceptable range support mispriming of gut microbiota as the underlying cause. False-positive pouches exhibited significantly higher Cp values than true positives for both assays (Noro-1: 26.6 vs. 11.1, p=0.013; Noro-2: 30.0 vs. 13.1, p<0.001), consistent with low-level off-target amplification. These findings highlight the high false discovery rate of the Noro-1 assay, identify bacterial species involved in mispriming, and demonstrate the need to redesign this assay to ensure reliable testing and improved patient care.