FDA clears second West Nile blood screening test

Aug 30, 2007 (CIDRAP News) – The US Food and Drug Administration (FDA) has announced the approval of a second automated test to screen donated blood and organs for West Nile virus (WNV).

The cobas TaqScreen WNV test, made by Roche Molecular Systems Inc. of Pleasanton, Calif., detects genetic material of the virus early in the infection, the FDA said in an Aug 28 press release. The Roche test is similar to the Procleix West Nile virus assay, which was approved by the FDA in December 2005 as the first stand-alone test to detect viral RNA in blood.

"This action is the culmination of the dedicated efforts of FDA, our sister agencies, blood establishments, and manufacturers to bring donor screening tests to the market for this increasingly common virus," said Jesse L. Goodman, MD, MPH, director of the FDA's Center for Biologics Evaluation and Research, in the press release. "As a result, blood centers and hospitals now have a choice of two FDA approved tests to screen for West Nile virus in donated blood and organs."

The TaqScreen test is approved for detecting the virus in plasma specimens from human donors of whole blood and blood components and from living donors of cells, reproductive cells, and other tissues, the FDA said. It is also intended for testing plasma specimens obtained from organ donors while the donor's heart is still beating. The test is not intended for use on cord blood samples or as an aid in diagnosing WNV infection.

WNV is usually transmitted to humans by mosquitoes, but it can also be spread by blood transfusion or organ transplantation.

Daniel O'Day, head of Roche Molecular Diagnostics, said in a Roche press release issued yesterday that the system has already been used under an investigational new drug application at 14 clinical trial sites that are testing blood from more than 100 donation centers.

Tranfusion-associated WNV transmission first emerged as a threat to the US blood supply in 2002. Roche said blood agencies began using investigational WNV nucleic acid amplification tests, including the Procleix and Roche systems, in June 2003.

The FDA said the approval comes in advance of guidance it is preparing on the use of licensed WNV screening tests for blood donors.

The United States had 4,269 WNV illnesses cases last year, a 42% increase over the previous year, according to the US Centers for Disease Control and Prevention (CDC). The number of WNV cases this year has been ahead of last year's pace, but fewer severe cases have been reported, the CDC reported 2 weeks ago.

As of Aug 21, the CDC had received 58 reports of blood donors who possibly were infected with WNV, the FDA said. In 2006, state and local health departments reported 361 presumably viremic blood donors to the CDC, according to CDC data.

Most people infected with WNV remain healthy, but about 20% fall ill with West Nile fever, which includes fever, headache, fatigue, body aches, and in some case a rash on the trunk, according to the CDC. About in 1 in 150 to 350 infected people suffers serious disease, including encephalitis.