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Multicenter Study Finds BioFire Joint Infection Panel Shows High Accuracy Despite Limitations

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COPENHAGEN – Data presented at the 33rd European Congress of Clinical Microbiology and Infectious Diseases on Monday found BioMérieux's BioFire Joint Infection Panel had high diagnostic sensitivity and accuracy. 

The BioFire PCR-based assay, which runs on the BioFire FilmArray 2.0 and BioFire Torch systems and returns results in an hour, received de novo authorization from the US Food and Drug Administration last May and CE marking under Europe's new In Vitro Diagnostic Regulations in July. The test includes 39 targets: 31 pathogens, including Gram-positive bacteria, Gram-negative bacteria, and yeasts, as well as eight antimicrobial resistance genes.

The data presented at ECCMID by Marjan Wouthuyzen-Bakker, an internist-infectiologist at University Medical Center Groningen, was collected during a 34-site prelaunch evaluation where hospitals used the test and were asked if the panel would have changed patient management. The evaluation included more than 1,527 synovial fluid samples, largely from adult patients, although 6 percent of the samples were from children. More than 50 percent of the samples were from knee joints, and 57 percent were from native joints with a quarter of the samples from prosthetic joints. 

For native joints, the BioFire test found an additional 73 positive samples — corresponding to 77 pathogens — compared to synovial fluid culture. Twelve samples, correlating to 12 pathogens, were positive via culture but missed by the panel, although Wouthuyzen-Bakker said that it was unclear whether the pathogens found in cultures were actually the causative agents for the infections. 

For prosthetic joints, the assay found an additional 38 positive samples, corresponding to 52 pathogens, compared to culture-based methods. Again, 12 samples were positive via culture but missed by the BioFire test. However, Wouthuyzen-Bakker said that in this evaluation there was no validation done to verify that the samples found to be positive by the BioFire test and negative by culture were true positives. 

Also, Staphylococcus epidermidis was found in 6 percent of the native joint cultures and 12 percent of prosthetic joint cultures. Wouthuyzen-Bakker noted that users of the BioFire panel should be aware that the assay does not detect S. epidermidis, although it is a "very common causative pathogen" in prosthetic joint infections. Adding more microorganisms would decrease the overall sensitivity of the panel, Wouthuyzen-Bakker said. 

Earlier this year, she published a paper in the Journal of Bone and Joint Infection evaluating the panel in 45 samples from patients suspected of having native septic arthritis or acute periprosthetic joint infections. The panel showed 100 percent specificity in all categories, with sensitivity of 83 percent for patients suspected of having native septic arthritis. Sensitivity was 73 percent for patients with suspected late acute periprosthetic joint infections and 30 percent for those with suspected early acute periprosthetic joint infections. She and her coauthors noted that there was a "clear clinical benefit" for the first two groups, but a low clinical benefit in the early acute infection patients "due to the absence of certain relevant microorganisms" from the panel, including S. epidermidis.

Researchers from eight sites in the UK and Ireland also recently published a study in the European Journal of Clinical Microbiology and Infectious Diseases that found the test had increased diagnostic yield for organisms included in the panel, with 98 samples having positive pathogen identification with the BioFire panel compared to 83 with routine culture methods. Like Wouthuyzen-Bakker, the researchers noted that the organisms detected by culture but not included in the BioFire panel, such as S. epidermidis, might be clinically significant in certain infections and could limit the value of the test for those infections. 

Physicians using the test were asked if the results of the BioFire test would have impacted patient management. Positive results would have had an impact in nearly 64 percent of the native joint infection cases and 70 percent of the prosthetic joint infection cases, Wouthuyzen-Bakker said.

"I can imagine that the major difference that it makes is you can target antibiotic treatment sooner," she added. Meantime, negative results would have had an impact in 31 percent of native joint cases and 20 percent of prosthetic joint cases.

In her presentation, Wouthuyzen-Bakker said that the panel "really aids in rapid diagnosis" and demonstrates "high diagnostic accuracy for those microorganisms that are included in the panel." She also noted that it would be good for a future study to compare the results of the test with tissue cultures.

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