By Ben Butkus
Quest Diagnostics subsidiary Focus Diagnostics this week announced CE marking and European availability for its Simplexa Flu A/B and RSV Direct test on the 3M Integrated Cycler, a new version of an existing test that eliminates the nucleic acid extraction step.
The new assay can be completed in just over an hour — about a quarter to a third as fast as its predecessor — with no loss in sensitivity and a simpler workflow, making it more conducive to direct testing at the point of care, the company said.
In addition, Focus plans to incorporate the technology into all future Simplex molecular diagnostics for infectious diseases, as well as potential tests outside of infectious diseases, such as the molecular genetics and coagulation arenas, Maurice Exner, vice president of research and development at Focus Diagnostics, told PCR Insider.
"We see this is as sort of our future here, with future products that we come out with in the molecular arena," Exner said. "We don't see a reason to necessarily ever go back to using [nucleic acid] extraction, because the non-extraction version is working very well."
Focus and 3M have been working together since 2009 to develop molecular diagnostic tests on 3M's Integrated Cycler, a benchtop instrument featuring a disc-shaped consumable that can process up to 96 samples in a 30- to 75-minute run depending on the analyte.
In the fourth quarter of last year Focus received the CE Mark and subsequent 510(k) clearance for the Simplexa Flu A/B & RSV assay, designed to aid in detecting and discriminating influenza A, influenza B, and respiratory syncytial virus infections from a patient nasopharyngeal swab (PCR Insider, 12/2/10).
Like many molecular diagnostic tests, the first version of Simplexa Flu A/B & RSV required a separate nucleic acid sample-extraction step, which is laborious and time-consuming, requires trained personnel, and tacks another hour or two onto the entire testing process.
To address this issue and make the test more conducive to use at the point of care, Focus developed and incorporated a technique to obviate the need for nucleic acid extraction. The company declined to share specific details about the technology due to its early and proprietary nature, but Exner provided PCR Insider with a basic overview.
"In comparison to extraction technology where you remove all the impurities or inhibiting substances to get purified DNA … we actually work to inhibit the inhibitory substances or problematic components that interfere with the reaction," Exner said. "By neutralizing them instead of removing them, we don't need to separate and purify the DNA from the bacteria or viruses."
The end result is that users of the new test need only aliquot PCR reagents and transport media containing a nasopharyngeal sample onto the consumable Simplexa disc, then insert it into the benchtop platform and run the test, Exner said.
"The new system is probably a two-minute setup and an hour PCR run, so you're essentially doing it in about an hour" versus three to four hours total for the previous version of the test, Exner said. "And the labor involved with the new test is very limited."
The Simplexa Flu A/B & RSV Direct is the first test from Focus to use the extraction-free technology. Exner said that the company already has available in Europe a Simplexa Clostridium difficile test using a similar technology, but it requires an extra heating step and thus does not have "quite the same sample-to-answer capability as the new disc."
The new direct flu and RSV test also contains just eight wells as opposed to most other Simplexa tests, which use 96 wells to achieve higher throughput. "The disc does meter liquids, so you don't have to pipette exact amounts," Exner said. "It's just very simple … compared to the 96-well version, which does require pipetting and reagent mixing, things like that."
The ultimate goal is to move the Simplexa Flu A/B & RSV Direct test closer to the patient, Exner said. "For flu, when you're sending it off to a centralized laboratory, it's really not helping the patient at all, because by the time they get the result back it's too late" to recommend an appropriate course of treatment, he said. "With this simplified format, you can get it closer to the patient in those laboratories with perhaps less expertise in doing molecular testing."
Eliminating nucleic acid sample prep is not particularly new in the molecular diagnostics space. For instance, Cepheid's GeneXpert system integrates nucleic acid extraction, amplification, and detection on a single cartridge, meaning users need only add a biological sample to the test cartridge before placing it on the testing platform. And numerous other vendors are developing benchtop sample-to-answer testing platforms, with the goal of reducing the time it takes to perform each step to minutes as opposed to hours.
But Simplexa Direct is different in that it is directly testing a sample rather than first extracting nucleic acid from it, which may actually confer additional benefits. Exner said that Focus has conducted extensive internal studies showing that the extraction-free test has equivalent sensitivity to the previous version. One reason for that "is we're not losing any sample during extraction. Typically, extraction processes aren't 100 percent efficient. The direct chemistry gives some benefits to this system … so we are not losing any sensitivity."
Focus has applied for a patent application on the direct testing method. The company is also planning to seek 510(k) approval for the direct version of the test in the US, but Exner declined to provide a timeline for such an endeavor.
The company also believes its direct testing technology can be incorporated into other types of molecular testing applications outside of infectious disease.
"We believe the technique works well on blood (including heparinized blood) and other specimen types, but have not tried it on fresh or [formalin-fixed paraffin-embedded] tissue yet," a Quest spokesperson told PCR Insider in an e-mail. "We're excited about the prospects of using the technology for non-infectious disease testing," she added, but declined to provide additional detail, citing competitive concerns.
Overall, "it's a different way of looking at molecular [testing] that is going to simplify it and really get it to the patient, rather than using it for something like epidemiology purposes," Exner summarized. "We've gone beyond some traditional thoughts about PCR that you can't do certain specimen types … and those are no longer issues for us."
Have topics you'd like to see covered in PCR Insider? Contact the editor at bbutkus [at] genomeweb [.] com.