West Nile Virus Antibody, IgM
Label Mnemonic: WNIGMCSF
Epic Lab Code: LAB8521
Downtime Form: A-1a Miscellaneous Request
Commercial Mail-out Laboratory
5231 RCP
356-8593
Specimen(s):
CSF
Collection Medium:
CSF collection kit
Minimum:
Preferred Minimum: 2 mL CSF in CSF container
Absolute Minimum: 0.15 mL CSF
Rejection Criteria:
Contaminated, heat-inactivated, or hemolyzed specimens.
Turn Around Time:
1-6 days upon receipt at reference laboratory
Reference Range:
0.89 IV or less: Negative - No significant level of West Nile virus IgM antibody detected.

0.90-1.10 IV: Equivocal - Questionable presence of West Nile virus IgM antibody detected. Repeat testing in 10-14 days may be helpful.

1.11 IV or greater: Positive - Presence of IgM antibody to West Nile virus detected, suggestive of current or recent infection.
Interpretive Data:
This test is intended to be used as a semi-quantitative means of detecting West Nile virus-specific IgM in CSF specimens in which there is a clinical suspicion of West Nile virus infection. This test should not be used solely for quantitative purposes, nor should the results be used without correlation to clinical history or other data. Because other members of the Flaviviridae family, such as St. Louis encephalitis virus, show extensive cross-reactivity with West Nile virus, serologic testing specific for these species should be considered.

The detection of antibodies to West Nile virus in cerebrospinal fluid may indicate central nervous system infection. However, consideration must be given to possible contamination by blood or transfer of serum antibodies across the blood-brain barrier.
Comments:
This is the preferred test for diagnosing West Nile encephalitis.
Methodology:
Semi-Quantitative Enzyme-Linked Immunosorbent Assay
CPT Code:
86788