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New Papers Compare Luminex's xTAG Gastrointestinal Pathogen Panel with Tests from Savyon, BioFire


NEW YORK (GenomeWeb) – Two new papers have assessed the ability of Luminex's xTAG Gastrointestinal Pathogen Panel and competitive offerings to detect infectious pathogens.

The first, authored by a team at Public Health Wales, appeared in the Journal of Medical Microbiology earlier this month and compared the performance of xTAG GPP with Sayvon Diagnostics' Gastrointestinal Infection Panel in 1,000 clinical stool samples.

Researchers at the Mayo Clinic in Rochester, Minn., carried out another study where they compared Luminex's assay with BioFire Diagnostics' FilmArray Gastrointestinal Panel in 500 samples. The paper was published earlier this month in the Journal of Clinical Microbiology.

Both studies add to a growing body of literature concerning new multiplex tests for the detection of enteric pathogens. Last month, for instance, a group of researchers from the University of Basel in Switzerland described their experience with the xTAG GPP in the journal Infection.

"The background was really to look at some molecular solutions to classical methodologies," said Sally Corden, a co-author on the JMM paper and head of the molecular diagnostics unit at Public Health Wales' microbiology lab in Cardiff. "We already had connections with Luminex from previous research projects and the Savyon link was established by [lead author] Michael Perry after meeting Savyon at an international conference," Corden told BioArray News this week.

Austin, Texas-based Luminex says its xTAG GPP can detect hospital-acquired infections, targeting a total of 15 gastrointestinal pathogens in a single bead array-based assay. The company garnered a CE-IVD mark for the test in 2012, followed by US Food and Drug Administration clearance last year for a version of the assay containing 11 pathogens for use on its LX 200 and benchtop MagPix instruments.

Savyon Diagnostics is a Gamida for Life company, and its Gastrointestinal Infection Panel targets eight pathogenic bacteria and parasites. The assay is run on Gamida's NanoChip microarray platform. Gamida acquired the NanoChip platform from the Elitech Group in 2010. The technology was originally developed by San Diego-based Nanogen.

Both assays interested Colden's lab, as conventional laboratory diagnostic methods are often "time-consuming and frequently suffer from low detection rates," the authors wrote in the paper. In their study, they tested a thousand stored diarrhea samples using both assays, gauging their performance against positive results for Camplobacter, Salmonella, Shigella, C. difficile, and Giardia that were obtained using common approaches such as enzyme-linked immunosorbent assays and culture.

The authors also evaluated the xTAG GPP assay concurrently with conventional methods for 472 clinical samples and its results aligned perfectly with positive findings obtained with culture and ELISA.

Overall, the authors seemed impressed by the two assays' performances.

"It provides a truly syndromic approach rather than bacteriology and virology departments working in isolation," Colden said of the two assays, calling them "far more effective and efficient."

That does not mean that Public Health Wales is going to start offering them in routine clinical use yet. Colden said that implementation of such tests is "not that straightforward in the NHS in Wales," but said that her lab is progressing towards offering them according to NHS and EU regulations.

Comparing Luminex and BioFire

At the Mayo Clinic, researchers sought to evaluate the performance of the xTAG GPP with another FDA-cleared assay, BioFire Diagnostics' FilmArray Gastrointestinal Panel, in 500 stool samples submitted to their lab for routine testing.

At the time the authors carried out the study, they used a prototype of the RT-PCR-based FilmArray GI panel that targeted 23 pathogens. The FDA cleared a version of the test containing 22 pathogens for clinical use in May.

Among 230 prospectively collected samples, routine conventional testing was positive for one or more GI pathogens in 19 samples, or about 8 percent of the total. In comparison, BioFire's test detected pathogens in 76 samples, or a third of the total, while Luminex's assay detected pathogens in 69 samples, or about 30 percent of those tested.

According to the authors, among 270 additional samples that had previously been tested using conventional approaches, both panels demonstrated high sensitivity of greater than 90 percent for the majority of targets. The authors also noted that the FilmArray and Luminex panels identified mixed infections in 21 percent and 13 percent of positive prospective samples, respectively, compared to only 8 percent by routine methods.

Matthew Binnicker, the corresponding author on the paper, declined to comment for this publication.

While the Mayo Clinic researchers compared the xTAG GPP and FilmArray tests head to head, Luminex executives have portrayed the two FDA-cleared diagnostics as serving different kinds of customers given differences in throughput and technology, with the xTAG GPP attracting high-volume laboratories and the FilmArray test catering to lower-volume labs.

"We're serving one volume segment, they're serving the other, and we're both working to educate the market about the benefits of the panel," CEO Patrick Balthrop said on an earnings call last month. "In the short, intermediate term it's actually been a net positive," he said of BioFire's market entry.