FDA in late August reported approval of a second test for the detection of West Nile virus (WNV) in blood and organs.

The cobas TaqScreen WNV test manufactured by Roche Molecular Systems (Pleasanton, California) is an automated test that is able to detect the genetic material of the virus itself early in the infection. Such nucleic acid testing improves blood and organ safety, detecting whether donated blood and organs have been infected even before the donor's body has begun to produce antibodies against the virus, according to a statement from the FDA. The test will compete with a WNV test from Gen-Probe (San Diego) in this market.

Roche said The company said that the diagnostic, enables detection of the virus "earlier in the infection cycle in donors who may show no symptoms of disease."

Chris Parkhouse, international business leader, blood screening, for Roche Molecular Diagnostics, told Biomedical Business & Technology that the cobas TaqScreen test utilizes different technology than its competitor. "Our test is PCR — polymerase chain reaction — and it is directed against the flavivirus family, which includes West Nile Virus. But it will also detect St. Louis Virus, Japanese encephalitis, Murray Valley [encephalitis virus] and one or two other viruses that have been shown to cause transfusion-transmitted infections," Parkhouse said.

"The other licensed assay" from Gen-Probe uses "transcription-mediated amplification" technology, Parkhouse said.

The development of this "broad spectrum" assay, he said, "stems back to early discussions with the FDA in 2003, when the agency pulled together manufacturers" to determine if they could produce such a test. For example, he said, St. Louis virus encephalitis is "associated with periodic outbreaks in the U.S."

The FDA said that while WNV infection is "common" in Africa, Asia and the Middle East, the U.S. was not impacted by the disease until 1999, when it first appeared in this country. Since then, the agency said, WNV has become "endemic" in most of the U.S., with from 1 million to 3 million cases between 1999 and 2006, according to the Centers for Disease Control and Prevention (Atlanta).

In a statement, Jesse Goodman, MD, director of FDA's Center for Biologics Evaluation and Research, said, "This action is the culmination of the dedicated efforts of FDA, our sister agencies, blood establishments and manufacturers to bring donor screening tests to market for this increasingly common virus.

Roche's test is approved for the detection of the virus in plasma specimens from human donors of whole blood and blood components and living donors of cells, reproductive cells and other tissues. The FDA said it is also intended for use in testing plasma specimens of organ donors when specimens are obtained "while the donor's heart is still beating."

"WNV has been especially virulent this year," the FDA said. "Although it is still early in the WNV season, 58 blood donors who are possibly positive for the virus have been reported to the CDC as of August 21, 2007." Since the introduction of the virus, the reported number of human cases of serious WNV in the U.S. "has grown steadily" from 62 in 1999 to 4,269 in 2006.

Now that there are two licensed tests, still -- according to Parkhouse -- WNV testing is not mandated in the U.S. It is expected that this new guidance, once it is issued, will essentially mandate WNV testing.

Gen-Probe received its first approval for a blood screening assay in late 2005, although at that time, U.S. blood centers had used Gen-Probe's Procleix WNV assay to screen more than 29 million units of donated blood since 2003.

Earlier this year, Gen-Probe's Procleix Tigris automated system also was cleared for WNV blood screening.

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