MDDI_Medical Device & Diagnostic Industry

MDDI, July 2016

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30 | JULY 2016 mddionline.com Image courtesy of Goldfinch4ever/iSTOCKPHOTO.COM Image courtesy of ALTONA DIAGNOSTICS IVD T he mosquito-borne Zika virus has turned into a pandemic across Latin America, and with the summer season ramping up in the United States, officials worry it is only a matter of time before mosquitoes start infecting people in the lower 48 states. Zika is such a worry because there is mounting evidence that infection during pregnancy can cause a serious birth defect called microcephaly, which causes infants to have abnormally small heads. Zika could also cause other severe fetal brain defects. No vaccine is available yet to protect against Zika, but some impor- tant strides are being made when it comes to diagnosing the disease. An FDA-Authorized Zika Test Quest Diagnostics in April announced FDA emergency use authoriza- tion for its Zika virus RNA qualitative real-time test (Zika RT-PCR test). The proprietary molecular test allows for detection of RNA from the Zika virus in serum from human blood. Quest's test, made by its Focus Diagnostics business, was the first commercial test to receive an emergency use authorization from FDA. Previously, the only FDA-authorized tests under emergency use authorization had to be used in CDC-qualified laboratories. Quest made its Zika RT-PCR test broadly available to physicians in May. The tests go to labs designated by Quest's Focus business and are certified to perform high complexity tests under the Clinical Laboratory Improvement Amendments (CLIA) of 1988. "Quest's expertise in molecular, infectious disease, and women's health diagnostics, and relationships with half of the country's phy- sicians and hospitals, allow us to quickly make useful tests widely available for clinical use. This capability uniquely positions Quest to complement the response of public health laboratories for Zika outbreaks where access to FDA authorized diagnostic tests can po- tentially influence the quality of patient management," Quests's vice president for R&D, Rick Pesano, MD, PhD, said in a news release. FDA's emergency use authorization letter for the test describes it as a real-time reverse transcriptase PCR (rRT-PCR) test. Here's how the agency described how it works: The Zika Virus RNA Qualitative Real-Time RT-PCR includes primers and dual-labeled hydrolysis (Taqman) probes targeting two separate nucleotide sequences within the Zika virus genome to be used in the in vitro quali- tative detection of Zika virus RNA isolated from human serum and any other authorized specimens. The purified nucleic acids are first reverse transcribed into cDNAs. In the process, the probes anneal to the specific target sequences located between the respective forward and reverse prim- ers. During the extension phase of the PCR cycle, the 5' nuclease activity of Taq polymerase degrades the probes, causing the reporter dyes to separate from the quencher dyes, generating fluorescent signals. With each cycle, additional reporter dye molecules are cleaved from their respective probes, increasing the fluorescence intensity. Testing Both Blood and Urine for Zika In May, FDA granted an emergency use authorization for the Re- alStar Zika virus RT-PCR kit, made by Altona Diagnostics GmbH (Hamburg, Germany). The test is meant to provide detection of RNA from Zika in serum from human blood or urine. The urine is collected alongside a patient-matched serum specimen. The workings of the RealStar test, as described in the FDA autho- rization letter, involve a primer and dual hydrolysis (Taqman ) probe. Purified nucleic acids are first reverse transcribed into cDNAs. The process has the probes anneal to specific target sequences located between the respective forward and reverse primers. According to the FDA letter: During the extension phase of the PCR cycle, the 5' nuclease activity of Taq polymerase degrades the probes, causing the reporter dye to separate from the quencher dye, generating fluorescent signals. With each cycle, additional reporter dye molecules are cleaved from their respective probes, increasing fluorescent activity. The tests go to labs certified to perform high-complexity tests under CLIA or by similarly certified non-U.S. labs. Altona Diagnostics's RealStar Zika RT-PCR kit can detect the virus in serum from human blood or urine. How Medtech Is Fighting Zika As fears about the mosquito-borne disease rise, the industry is responding with new diagnostics. CHrIs NewMArker

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