West Nile Virus: Test for Diagnosis

The Food and Drug Administration (FDA) has cleared the first test for use as an aid in the clinical laboratory diagnosis of West Nile virus infection. The West Nile Virus IgM Capture ELISA is intended for use in patients with clinical symptoms consistent with viral encephalitis/meningitis.

"Emerging infectious diseases such as West Nile virus present a challenge to the public health community," said Tommy G. Thompson, Secretary of Health and Human Services. "When industry and government collaborate closely to meet a public health need, the resulting new technology will strengthen our joint efforts to confront diseases earlier and should lower rates of infection."

The new test works by detecting the levels of a particular type of antibody, IgM, to the disease in a patient's serum. IgM antibodies can be detected within the first few days of the onset of illness and can assist in the diagnosis of these patients.

" The rapid review and approval of this blood test, which uses antibody levels to identify persons who were recently exposed to West Nile virus, reflects FDA's commitment to making safe and effective medical products available promptly," said FDA Commissioner Mark B. McClellan, M.D.,Ph.D. "This test provides a useful tool to combat the important public health problem of West Nile virus infection, just in time for the start of the West Nile season."

The PanBio West Nile IgM assay was evaluated using over 1000 patient sera, which were tested at four different clinical sites. The test correctly identified antibody in up to 90 to 99% of West Nile virus disease cases. Because detection of antibody is not always specific in patients with acute viral infections, this test is considered presumptive and should be confirmed by more specific testing.