Evaluation of false positive enteric viruses results from the BIOFIRE® FILMARRAY® gastrointestinal PCR panel

The BioFire® FilmArray® Gastrointestinal (GI) Panel targets 22 pathogens associated with acute gastroenteritis (AGE). While the Veterans Affairs SUPERNOVA surveillance platform uses this assay to test stool specimens from hospitalized Veterans across five U.S. medical centers, increasing reports of false positives, particularly for norovirus, have raised concerns regarding the assay's accuracy.

To verify BioFire®-positive viral results from the SUPERNOVA study using molecular reference methods at the Centers for Disease Control and Prevention (CDC).

A total of 415 stool specimens (2018-2023) from both hospitalized and outpatient Veterans with AGE that tested positive by BioFire® GI panel for at least one of five viruses (norovirus, rotavirus, sapovirus, astrovirus, or adenovirus 40/41) were retested using CDC reference methods, including RT-qPCR and conventional RT-PCR with Sanger sequencing. Specimens were considered true positive when confirmed by two of the three testing methods.

Of the 415 specimens, 327 (78.8%) were confirmed positive for at least one virus. Norovirus was the most frequent (n = 207; 63.3%), followed by sapovirus (39; 11.9%), rotavirus A (37; 11.3%), astrovirus (36; 11.0%), and adenovirus 40/41 (10; 3.1%). False-positive rates were highest for norovirus (26.5%), followed by rotavirus (21.3%) and sapovirus (18.8%). Norovirus false-positives were more frequent in hospitalized patients (35.5%) than in outpatients (19.2%), particularly among individuals aged 40-60 years. Norovirus false positives trended upward starting in 2021.

These results confirm performance concerns with the BioFire® GI Panel, particularly for norovirus, the most frequently identified virus. Confirmatory testing of questionable positives should be considered.