( inical symptoms. These observations ex...)West Nile Virus Screening and Diagnostics Technology Emerges In Step with North American Outbreak,Health

Although WNV is transmitted primarily by mosquitoes, transmission has occurred through transfused blood products. Since 2003 donor mini-pools have been tested by NAT utilizing two test manufacturers approved by the FDA under the investigational new drug mechanism (TaqScreen WNV test, Roche Molecular Systems, Inc.; Procleix WNV assay, GenProbe, Inc.). Although screening has substantially reduced the risk of transfusion associated transmission, there have been screening failures because of low levels of viremia in asymptomatic donors and the use of mini-pools.

The most recent guidelines for diagnosis in patients with suspected WNV infections include ELISA detection of IgM and IgG antibodies to WNV in serum or cerebrospinal fluid. Because of cross reactivity with other flaviviruses, positive results must be confirmed with a plaque reduction neutralization test (PRNT). FDA-approved ELISA kits for detection of antibody are available from Focus Diagnostics, PANBIO Limited and InBios International, Inc. A promising microsphere immunoassay that is more specific for WNV has been described in the literature, but is not available commercially.

The intended use of the FDA approved ELISAs offered by all 3 companies is similar: the assays are intended to qualitatively detect antibodies in sera of patients having symptoms of meningioencephalitis as an aid in the presumptive diagnosis of WNV infection. Positive results must be confirmed by the PRNT or using current CDC guidelines.

Focus Diagnostics offers the West Nile Virus IgM Capture DxSelect, and the West Nile Virus IgG DxSelect. The IgM capture ELISA procedure utilizes wells coated with rabbit anti-human IgM to which diluted samples are added. After incubation and washing, recombinan
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