ARUP's Laboratory Test Directory

0050234: West Nile Virus Antibody, IgG by ELISA, Serum

Test Mnemonic: WNILE IGG
Methodology: Enzyme-Linked Immunosorbent Assay

Performed: Tue, Fri

Reported: 1-5 days

Specimen Required:  
Collect: One 4 mL SST.

Transport: 1 mL serum at 2-8°C. (Min: 0.5 mL) Submit specimen in an ARUP Standard Transport Tube.

Pediatric Collection/Transport: 0.15 mL serum at 2-8°C.

Remarks: Separate serum from cells ASAP. Acute and convalescent specimens must be labeled as such; parallel testing is preferred and convalescent specimens must be received within 30 days from receipt of the acute specimens. Please mark specimen plainly as "acute" or "convalescent."

Unacceptable Conditions: Plasma.  Severely lipemic, contaminated, heat-inactivated, or hemolyzed specimens.

Stability: After separation from cells: Ambient: 2 days; 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.
1.30-1.50 IV: Equivocal - Questionable presence of West Nile virus IgG antibody detected.  Repeat testing in 10-14 days may be helpful.
1.51 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 samples 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 also be performed.

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.



CPT Code(s):
86789