West Nile Virus IgM, Serum
Test Mnemonic
WESTM
CPT Codes
- 86788 - QTY (1)
LOINC ®
38166-5
Includes
- West Nile Virus IgM
Performing Laboratory
ARUP
Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 1 mL | Serum | SST (Gold) | Refrigerated | Separate serum from cells ASAP or within 2 hours of collection. |
Minimum Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 0.15 mL |
Stability
| Environmental Condition | Description |
|---|---|
| Ambient | 48 hours |
| Refrigerated | 2 weeks |
| Frozen | 1 year (avoid repeated freeze/thaw cycles) |
Days Performed
Sun, Tues, Fri
Turnaround Time
2 - 7 days
Methodology
| Name | Description |
|---|---|
| Enzyme-Linked Immunosorbent Assay (ELISA) |
Reference Range
| West Nile Virus IgM | |||||
|---|---|---|---|---|---|
| Sex | Age From | Age To | Type | Range | Range Unit |
| 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. |
Special Info
Parallel testing is preferred and convalescent specimens must be received within 30 days from receipt of the acute specimens. Mark specimens plainly as "acute" or "convalescent."
Clinical Info
This test is intended to be used as a semi-quantitative means of detecting West Nile virus-specific IgM in serum 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. Seroconversion between acute and convalescent sera is considered strong evidence of current or recent infection. The best evidence for infection is a significant change on two appropriately timed specimens, where both tests are done in the same laboratory at the same time.