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Swedish Study Evaluates BD Enteric Parasite Panel

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NEW YORK (GenomeWeb) – An evaluation of Becton Dickinson's enteric parasite panel has shown the test has good specificity and sensitivity for two out of three targets. Researchers at Örebro University in Sweden also determined that a third target was less sensitive, yet still as sensitive as microscopy.

Published last week in the Journal of Clinical Microbiology, the small study "demonstrated the clinical value, ease of implementation, and outstanding clinical performance [with respect to] sensitivity, specificity, and time to result, of the BD MAX Enteric Parasite Panel in a routine laboratory setting," Nikos Pavlidis, global business leader of Lab Automation for Diagnostic Systems at BD, told GenomeWeb.

This level of performance was demonstrated against the standard of care, and the test improved testing efficiencies and freed up valuable expert resources, Pavlidis noted.

The Enteric Parasite Panel was cleared by the US Food and Drug Administration in September. It detects DNA from Cryptosporidium — both C. hominis and C. parvumEntamoeba histolytica, and Giardia lamblia, which is also called Giardia intestinalis, in unpreserved and formalin-fixed stool specimens. The panel runs on the BD Max system, which has automated sample prep, extraction, amplification, and detection.

The Swedish evaluation examined a total of 132 clinical samples. Half had been previously tested using an in-house PCR and stored frozen, while the other half were previously assessed for the presence of parasite ova and cysts and were stored in formalin-containing SAF transport medium.

The enteric parasite panel is validated for testing unpreserved or 10 percent formalin-fixed stool specimens from symptomatic patients with suspected gastroenteritis, enteritis, or colitis, Pavlidis pointed out.

"Although the SAF transport medium used in this study is formalin-based, the performance of the EPP using this exact formulation isn't known," he said.

The BD panel, which took about 3.5 hours to run including automated data analysis, was compared to the past results, and a different in-house PCR was used to reconcile discrepancies.

Results were in complete agreement with previous PCR results with the exception of G. intestinalis. For that parasite, four out of 12 samples were not detected. The researchers confirmed the presence of parasite DNA using the second PCR in three of these samples, but the fourth did not have enough remaining material.

For the samples that had been previously assessed with microscopy, G. intestinalis and Cryptosporidium were confirmed with the BD panel, but the test also called one specimen positive for G. intestinalis that was not detected under the microscope.

All 12 samples that had past microscopic evidence of E. histolytica were reported negative by the BD panel and were subsequently verified positive for the E. dispar strain of the parasite by PCR.

The researchers concluded that storing samples in the freezer could have affected the G. intestinalis sensitivity, but, overall, the test is an improvement over microscopy, which has low sensitivity and can't rule out infection in some cases if only parasite cysts are present. Microscopy also requires highly skilled technicians and is time consuming, the authors noted.

Pavlidis echoed these conclusions. "Since frozen stability of either unpreserved or 10 percent formalin-fixed stool specimens has not been established for the EPP, utilizing frozen specimens may have contributed to the G. intestinalis detection rate observed in this study," he said. The panel has been validated for samples transported and stored for 48 hours at 2 to 25 degrees Celsius or for 5 days at 2 to 80 degrees.

More than 1,600 specimens were tested in the multi-center prospective clinical trial used to support US FDA submission and clearance of the EPP, Pavlidis said. 

That study utilized a composite reference method algorithm to calculate assay performance, "making it possible to further optimize the cut-off for the EPP Giardia lamblia target and resulting in sensitivities of 95.5 percent and 94.4 percent for preserved and unpreserved specimens, respectively," according to Pavlidis.

Ultimately, the Swedish group noted that the test will likely be used primarily for cases of travelers' diarrhea, but it may be considered as a primary diagnostic test when waterborne Cryptosporidium infections are suspected, since this parasite may be underdiagnosed in Sweden.

BD's Enteric Parasite Panel is one of several the firm has developed or is developing for its BD Max system, and its approach to multiplex testing differs somewhat from other competitors. While some firms have syndromic panels that can test for bacteria, viruses, fungi, or parasites, BD is developing smaller, more focused panels.

Cleared last year, it's Enteric Bacterial Panel was shown in a recent assessment at Cincinnati Children's Hospital to save time and money compared to culture, and it also performed favorably in a large, multi-site clinical evaluation published earlier this year. Its Enteric Viral Panel primers and probes kit, meanwhile, is offered with partner Diagenode, as previously reported.

"The FDA-cleared BD MAX assays for enteric bacterial, parasitic pathogens, and Clostridium difficile are designed as an aid for selective, targeted diagnosis of enteric infectious diseases, an approach that is consistent with the recommendations of the American Society of Microbiology, the Infectious Disease Society of America, and the College of American Pathologists," Pavlidis said, adding, "The BD MAX assays can be used as standalone panels ... or in any combination, providing a high degree of flexibility and efficiency to the diagnostic labs to perform testing based on clinical indications."

Panels currently in development for the BD Max system include extended Enteric Bacterial and Enteric Viral panels, the firm's CT/GC/TV test, which was CE-marked earlier this year, and a Vaginitis/Vaginosis assay. Each is anticipated to be available over the next one to three years.

The firm also launched a set of reagents for LDT development on the BD Max last year, and "our partners continue to develop the menu on the BD MAX system, leveraging the unique open system architecture of the BD MAX solution," Pavlidis said.

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