The assays — the NP2 and VP40 RT-qPCR tests from the US Centers for Disease Control and Prevention described previously, and BioMérieux's BioFire Diagnostics FilmArray BioThreat (BT) panel and the FilmArray BT E-panel that were approved for use last October — are among the eight in vitro diagnostics to detect viral RNA granted EUA since the Secretary of Health and Human Services declared that the Ebola virus presents a national security threat against the United States population.
The study was conducted by researchers from the US Centers for Disease Control and Prevention, Emory University School of Medicine, The University of Nebraska Medical Center, and the Nebraska Public Health Laboratory.
Many of the patients treated in the US during the recent Ebola outbreak — the majority of whom were medical evacuees from West Africa, where the outbreak killed more than 11,000 people — were treated at Emory and the Nebraska Medical Center.
The study assessed percent agreement among the four assays, using titers of Ebola-spiked whole blood as well as clinical specimens of whole blood, plasma, and urine from infected people.
For each of 38 whole blood titers, there was complete agreement.
FilmArray and the CDC RT-qPCR tests showed 85 percent agreement on whole blood from infected patients, but 90 percent agreement when FilmArray was tested with whole blood and matched plasma was tested with RT-qPCR.
There was an 85 percent agreement on urine specimens. Agreement between the NP2 and FilmArray assays was 100 percent on 30 specimens derived from initial stages of the disease.
The authors note that there were eight discordant results in the prospective evaluation of 60 clinical specimens from six of the patients they treated — four samples were only positive with FilmArray and four only with the CDC tests.
Ultimately, the researchers concluded that the FilmArray was advantageous because the tests are rapid and easy to use.
FilmArray tests one sample at a time, while the standard RT-qPCR can be run in batches of 96. But the FilmArray takes one hour and RT-qPCR takes three hours and requires more technical expertise.
"Reduced manipulation of clinical specimens, ease of use, and rapid turnaround time make [FilmArray] an appropriate screening test for healthcare institutions and public health laboratories that lack qRT-PCR capability," they wrote.