Diagnostics & Imaging Week
The FDA late last week reported the approval of a new laboratory test, developed by the Centers for Disease Control and Prevention (CDC; Atlanta), to diagnose H5 strains of influenza in patients suspected to be infected with the virus.
The test, named Influenza A/H5 (Asian lineage) Virus Real-time RT-PCR Primer and Probe Set, provides preliminary results on suspected H5 influenza samples within four hours once a sample arrives at the lab and testing begins. Previous tests require at least two to three days to render results. If the presence of the H5 strain is identified, further testing is conducted to identify the specific H5 subtype (e.g., H5N1), according to the FDA.
"We've been working on developing the test for some time, because having a rapid diagnostic test for H5 is vital for a public health response and identifying the potential cases of bird flu or influenza viruses of Asian lineage," Jennifer Morcone, a CDC spokeswoman, told Diagnostics & Imaging Week. In a follow-up e-mail, she said the test had been in development over the past two years.
Morcone added: "This tests detect the presence of a very small amount of the H5 virus or the Asian lineage influenza A virus material from a clinical sample of nose or throat swab with very high sensitivity." She described the sensitivity as being able to detect "as low as 100 copies of virus genes, or even less."
Since December 2003, more than 160 human cases of avian flu caused by the H5N1 strain of influenza have been reported in Thailand, China, Vietnam, Cambodia, Indonesia, Turkey and Iraq. More than half of the people infected with the H5N1 virus have died, with nearly all cases believed to have been caused by exposure to infected poultry. The concern is that H5N1 will evolve into a virus capable of human-to-human transmission and lead to an influenza pandemic.
Morcone told D&IW that the test tests only for the H5 virus, but not down to the "N1" level, or the particular strain of the H5 virus. However, prior to development of the CDC's test, a clinical sample would have to be taken and grown in culture, with the results taking "several days to weeks, depending on the test."
The test is available now, Morcone said, and the CDC is deploying it through the agency's Laboratory Response Network (LRN). Domestically the LRN is a system of about 140 labs in all 50 states. LRN labs have special experience and training in molecular testing methods, special bio-safety facilities and containment procedures as well as communication networks connected to public health programs across the country.
CDC has shared the test technology with the World Health Organization (Geneva) and its collaborating centers around the world.
"This laboratory test is a major step forward in our ability to more quickly detect cases of H5 avian influenza and provides additional safeguards to protect public health," HHS Secretary Mike Leavitt said in a prepared statement. "[T]he availability of this new test gives us one more tool to keep up with the ever changing nature of influenza viruses."
"Preparing for a possible flu pandemic is a top priority for our nation, and FDA acted quickly to evaluate and expedite CDC's request for approval of this test," said Dr. Andrew von Eschenbach, acting FDA commissioner. "Using flexible regulatory authorities, FDA was able to prioritize this expedited approval based on the clear critical need without compromising the quality or integrity of the FDA review process."
The test will be distributed to LRN-designated laboratories to enhance early detection and surveillance activities as well as increase laboratory response capacity associated with a potential pandemic.
"The use of this test by laboratories that are part of the LRN, in conjunction with other laboratory testing and clinical observations, may enable earlier detection of influenza cases caused by this specific virus and allow public health agencies to investigate sources of infection and more quickly respond with control and prevention activities," said CDC Director Dr. Julie Gerberding.
Testing for this virus is indicated when a patient has symptoms of severe respiratory illness and a risk of exposure (e.g., direct contact with sick, dead or infected poultry in a country with outbreaks of influenza H5N1 among poultry).
The CDC recommends that testing for influenza A/H5 be considered on a case-by-case basis "in consultation with local or state health departments. The full recommendations are available at www.cdc.gov/flu/avian/.
Qiagen (Venlo, the Netherlands) in early November reported the global launch of two test kits for the detection of the much-feared virus. The company's molecular test for humans, called the artus Influenza/H5 kit, was being offered by the company's sales team focused on molecular diagnostics testing, Dr. Solveigh Mahler, director of investor relations and public relations for Qiagen, told D&IW.
In addition, Tm Bioscience (Toronto) has reported development of an upper respiratory viral panel that it said detects all of the major human respiratory viruses, including H5N1 (avian flu) and SARS Corona, or severe acute respiratory syndrome. And Quest Diagnostics (Lyndhurst, New Jersey) said it has developed a test to detect the avian flu virus (Diagnostics & Imaging Week, Nov. 10, 2005).