Ordering Recommendation

Not recommended for diagnosing acute West Nile infection. May be useful for determining past infections/exposure.

Mnemonic
WNILE IGG
Methodology

Semi-Quantitative Enzyme-Linked Immunosorbent Assay

Performed

Sun, Tue, Fri

Reported

1-4 days

New York DOH Approval Status
This test is New York DOH approved.
Specimen Required
Patient Preparation
Collect

Serum separator tube.

Specimen Preparation

Separate serum from cells ASAP or within 2 hours of collection. Transfer 1 mL serum to an ARUP Standard Transport Tube. (Min: 0.15 mL) Parallel testing is preferred and convalescent specimens must be received within 30 days from receipt of the acute specimens. Mark specimen plainly as "acute" or "convalescent."

Storage/Transport Temperature

Refrigerated.

Unacceptable Conditions

Contaminated, heat-inactivated, hemolyzed, or severely lipemic specimens.

Remarks
Stability

After separation from cells: Ambient: 48 hours; Refrigerated: 2 weeks; Frozen: 1 year (avoid repeated freeze/thaw cycles)

Reference Interval

1.29 IV or less: Negative - No significant level of West Nile virus IgG antibody detected.
1.30-1.49 IV: Equivocal - Questionable presence of West Nile virus IgG antibody detected. Repeat testing in 10-14 days may be helpful.
1.50 IV or greater: Positive - Presence of IgG antibody to West Nile virus detected, suggestive of current or past infection. 

Interpretive Data

This test is intended to be used as a semi-quantitative means of detecting West Nile virus-specific IgG in serum specimens in which there is a clinical suspicion of West Nile virus infection.  This test should not be used solely for quantitative purpose, 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.

Compliance Category

FDA

Note
Hotline History
N/A
CPT Codes

86789

Components
Component Test Code* Component Chart Name LOINC
0050234 West Nile Virus Ab, IgG, Ser 38997-3
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
Aliases
  • Arbovirus
  • Flavivirus
  • WNV IgG
West Nile Virus Antibody, IgG by ELISA, Serum