West Nile IgM and St. Louis Encephalitis IgM Testing

The Missouri State Public Health Laboratory conducts IgM antibody testing for various arboviruses including West Nile Virus (WNV) and St. Louis encephalitis (SLE) on serum and cerebrospinal fluid (CSF) samples.

Virology

WN IgM and SLE IgM antibody detection on single acute serum, convalescent serum, or CSF using Microsphere Immunoassay (MIA).

All specimens marked for Arbovirus serology will only be tested against antigens of the Flavivirus group, which include WNV and SLE.

Virus Serology Kit

The ideal timing to collect acute serum is 3 to 10 days after onset of symptoms.

Collect CSF as soon as possible after onset of symptoms.

At least 1 ml of serum and 1.5 ml of CSF is required for serological testing.

Specimens received within 10 days of collection and stored at refrigeration temperature should be shipped on freeze pillows. Specimens that have been frozen or being shipped after 10 days of collection should be shipped on dry ice.

Serum, CSF

Virology Test Request Form

Positive (CSF) - Indicates recent infection.

Positive (Serum) - Indicates infection.*

Nonspecific - Results of borderline significance (Convalescent specimen required for proper interpretation).

Negative - Results fail to indicate an infection with WNV or SLE.

* West Nile Virus IgM antibody may remain for more than one year. Thus it will be difficult to determine if a positive IgM (from serum) is from an acute WNV infection. In this case clinical correlation is required to determine infection.

• Specimen not properly labeled
• Quantity Not Sufficient for testing
• Hemolyzed specimen
• Improper storage/transport of specimen

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3 to 10 days after receipt of specimen. May vary during high and low volume testing periods.

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