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Dutch Firm PathoFinder's Multiplex STD Assay Performs Well in Comparative Study

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By Ben Butkus

A multiplex PCR-based assay being developed by Dutch firm PathoFinder to simultaneously detect seven sexually transmitted diseases has comparable clinical sensitivity to more conventional single- and duplex PCR assays for the pathogens, according to a recently published research study.

According to the study's authors, the test is suitable for the routine detection of the included STDs at a relatively low cost due to multiplexing; however, its performance needs to be further assessed in larger populations or groups with a higher incidence of certain STDs.

Such studies will also help support PathoFinder's pursuit of the CE Mark for In Vitro Diagnostics for the product, called STDFinder, in order to bring it to market in Europe next year, CEO Guus Simons told PCR Insider in a recent e-mail.

"PathoFinder is only selling CE-IVD-compliant products and currently we are in the process of getting CE-IVD compliance of our STDFinder," Simons said. He noted that because the test includes Chlamydia trachomatis, which is an Annex II List B pathogen according to the European IVD Directive, it has "additional regulatory requirements."

Simons said that the company also plans to eventually tackle the US market, but that it couldn't currently afford such an endeavor given the relatively high regulatory hurdle in the US. "At the moment we cannot afford it but maybe next next year we can," Simons said. "We definitely need a good strategic partner in the US."

STDFinder uses the company's MultiFinder technology platform, which enables the detection and differentiation of as many as 25 viral and bacterial targets in a single assay. MultiFinder combines multiplex ligation-dependent probe amplification technique owned by Dutch firm MRC-Holland, along with capillary electrophoresis to analyze the resultant PCR products.

According to Simons, PathoFinder holds a worldwide, exclusive license to the MLPA method for use in the infectious disease market. MRC-Holland, meantime, markets various gene expression analysis kits that use MLPA in research and diagnostic applications. To wit, a team from Maastricht University is using MLPA to develop an inexpensive prenatal blood test to detect chromosomal abnormalities such as trisomy 21 (PCR Insider, 7/1/10).

In a paper published in the September issue of Diagnostic Microbiology and Infectious Disease, clinical researchers from Ghent University Hospital and other academic and non-profit institutions in Belgium and Rwanda evaluated the STDFinder assay's ability to simultaneously detect seven STD pathogens — Neisseria gonorrhoeae, C. trachomatis, Trichomonas vaginalis, Mycoplasma genitalium, Treponema pallidum, and herpes simplex virus type 1 and 2 — in 242 vaginal swabs taken from infertile women treated at Rwanda's Kigali Teaching Hospital.

The researchers compared the STDFinder results with those obtained using a variety of commercial or previously published species-specific single or duplex PCR assays, including the Abbott Real-Time CT/NG, Gen-Probe Aptima Combo 2, Argene real-time PCR HSV1/2, and Abbott Real-Time HSV1/2 assays; as well as a number of laboratory-developed assays.

The researchers explained that while culture methods are still generally considered to be the gold standard for this type of pathogen detection, several studies have shown that nucleic acid amplification tests have a higher detection rate for sexually transmitted pathogens and thus may be the more valuable comparator. The scientists also noted that each of the tests selected for comparison amplified different targets than STDFinder.

Also, in order to increase the study's ability to evaluate STDFinder's performance, the researchers also used it to test an additional 80 specimens — 31 positive for either C. trachomatis or N. gonorrhoeae; and 49 negative for both – that had been previously tested using Abbott's Real-Time CT/NG assay.

Compared to the various reference tests, STDFinder demonstrated specificities and sensitivities of 100 percent for N. gonorrhoeae, C. trachomatis, and M. genitalium; 90.2 percent and 100 percent, respectively, for Trichomonas vaginalis; and 96.1 percent and 100 percent, respectively, for HSV-2. None of the tested specimens was positive for HSV-1 or Treponema pallidum by either the STDFinder assay or the comparator method.

Overall, the results showed that STDFinder "has comparable clinical sensitivity to the conventional single and duplex real-time PCR assay and is suitable for the routine detection of a broad spectrum of these STDs at relatively low cost due to multiplexing," the researchers wrote in their paper.

The scientists also underscored the fact that the multiplexed nature of STDFinder would hold an advantage over existing molecular methods in terms of cost; and that it may have the added benefit of detecting co-infections.

However, they also noted that "further testing of a larger population, or a population with a higher incidence of certain STDs, and using different specimens, would be required to achieve the power necessary to adequately assess this assay."

PathoFinder's Simons told PCR Insider that the company is currently performing such additional validation studies in hopes of bringing STDFinder to market in 2012.

If successfully commercialized, STDFinder would not be PathoFinder's first marketed product to use the MultiFinder platform. The company has also developed a series of CE-Marked panels for respiratory disease detection called RespiFinder.

In December, PathoFinder said that it had signed an agreement with Life Technologies to sell these panels as Applied Biosystems TrueScience RespiFinder panels in most European countries covered by the CE IVD Directive; as well as in Latin American, Asia Pacific, Australia, New Zealand, and Africa. PathoFinder and its distributors continue to sell RespiFinder products under PathoFinder's label in France, Italy, Belgium, and the Netherlands.

The RespiFinder panels can detect up to 19 of the most common respiratory viruses and bacteria, including influenza virus, respiratory syncitial virus, parainfluenza virus, and Bordetella pertussis in a single reaction followed by fragment analysis in as little as seven hours, according to the company.

And even as PathoFinder is working to penetrate the diagnostic testing market with its MultiFinder technology, it is developing a next-generation technology called SmartFinder, which enables the detection of MultiFinder probes using real-time PCR instruments such as Roche's LightCycler 480 or Qiagen's RotorGene Q.

"We are also transforming our STDFinder to a real-time PCR format using our SmartFinder technology," Simons said. "A multiplex of eight targets — seven pathogens and an internal amplification control — in a single reaction on a real-time PCR machine."


Have topics you'd like to see covered in PCR Insider? Contact the editor at bbutkus [at] genomeweb [.] com.

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